Genetic, hormonal and metabolic aspects of PCOS: An update

Abstract

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder affecting 5–10 % of women of reproductive age. It generally manifests with oligo/anovulatory cycles, hirsutism and polycystic ovaries, together with a considerable prevalence of insulin resistance. Although the aetiology of the syndrome is not completely understood yet, PCOS is considered a multifactorial disorder with various genetic, endocrine and environmental abnormalities. Moreover, PCOS patients have a higher risk of metabolic and cardiovascular diseases and their related morbidity, if compared to the general population.

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R E V I E W Open Access
Genetic, hormonal and metabolic aspects
of PCOS: an update
V. De Leo
*
, M. C. Musacchio, V. Cappelli, M. G. Massaro, G. Morgante and F. Petraglia
Abstract
Polycystic ovary syndrome (PCOS) is a complex endocrine disorder affecting 5–10 % of women of reproductive age.
It generally manifests with oligo/anovulatory cycles, hirsutism and polycystic ovaries, together with a considerable
prevalence of insulin resistance. Although the aetiology of the syndrome is not completely understood yet, PCOS
is considered a multifactorial disorder with various genetic, endocrine and environmental abnormalities. Moreover,
PCOS patients have a higher risk of metabolic and cardiovascular diseases and their related morbidity, if compared
to the general population.
Keywords: PCOS, Genetic, Insulin-resistance, Hyperandrogenism, Infertility, Metformin, Oral contraceptives,
Myo-inositol
Background
Definition and diagnostic criteria
Polycystic ovary syndrome (PCOS) is the most common
endocrine disorder in women and major cause of an-
ovulatory infertility. PCOS patients can present a wide
range of signs and symptoms, which make difficult the
precise grading of the condition. Diagnosis of PCOS is
currently based on the criteria of the ESRHE/ASRM
Rotterdam consensus meeting in 2003 [1], which broad-
ened the previous NIH classification of 1990 [2]. It based
on at least two of the following features: oligo-
anovulation, hyperandrogenism and polycystic ovaries by
ultrasound [1]. In 2006, the Androgen Excess Society
(AES) set up a committee of experts to review all the
data published on PCOS for the purpose of simplifying
diagnosis [3]. The AES criteria require clinical and/
or biochemical hyperandrogenism simultaneously
with oligo/anovulation and ultrasonographic evidence
of polycystic ovaries.
Although the aetiology of PCOS is not completely
understood yet, PCOS is considered a multifactorial
disorder with various genetic, metabolic, endocrine and
environmental abnormalities [4]
There is increasing evidence suggesting that PCOS
affects the whole life of a woman, can begin in utero in
genetically predisposed subjects, it manifests clinically at
puberty, continues during the reproductive years. It can
also expose patients to increased risk of cardiovascular
disease, hypertension, diabetes and other metabolic com-
plications, especially after menopause [4]. During the
fertile period it may cause anovulatory infertility and
could be associated with increased prevalence of gesta-
tional complications, such as miscarriage, gestational
diabetes and preeclampsia [5]. Early diagnosis is there-
fore crucial by enabling close follow-up and in an at-
tempt to reduce the risk of such complications.
It is now widely recognised that insulin resistance,
manifesting above all in obese or overweight women,
but often also in lean PCOS women, is one of the key to
this complex disorder. It determines hyperandrogenism
by acting synergically with luteinising hormone (LH) on
ovarian steroidogenic enzymes and on sex hormone-
binding globulin (SHBG) production by the liver [5].
Diagnostic workup includes hormonal evaluation of
androgen levels, clinical evaluation of hirsutism trough
Ferriman-Gallwey score and ultrasonographic examin-
ation of the number of antral follicles and ovarian vol-
ume. Insuline resistance should be evaluated by HOMA
INDEX (product of fasting plasma insulin [mU/L] and
glucose [mmol/L] concentrations divided by 22.5). Fu-
ture diagnostic approaches could be ultrasonographic
3D evaluation of follicles and is under discussion the
role of anti-mullerian hormone (AMH) [6, 7].
* Correspondence: vincenzo.deleo@unisi.it
Department Molecular Medicine and Development, University of Siena,
Policlinico Le Scotte, Viale Bracci, 53100 Siena, Italy
© 2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
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reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38
DOI 10.1186/s12958-016-0173-x
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Etio-pathogenesis and pathophysiology: role of genetic,
environmental and endocrine factors
Genetic and endocrine factors, together with environ-
mental influences. In the research of etiopathogenesis of
the syndrome and in the subsequent pathophysiological
expression play a role genetic and endocrine as well as
environmental factors. The most interesting hypothesis
was proposed by Franks et al. [4], who defined PCOS as
a genetically determined ovarian pathology characterised
by over-production of androgens and manifesting het-
erogeneously according to the interaction of this genetic
“predisposition”with other genetic and environmental
factors. This hypothesis is persistent by the finding of
polycystic ovaries in pre-pubertal girls [4, 8]. Studies in
rhesus monkeys have demonstrated that exposure of foe-
tuses to high levels of androgens during intrauterine life
determines the onset of clinical manifestations of PCOS
during adolescence. Studies in sheep have shown that an
excessive androgen exposure during foetal life influences
early ovarian follicular activity and it may explain the
typical altered folliculogenesis shown in PCOS [4, 8].
The aforementioned observations may suggest that ex-
posure of the foetal hypothalamus-pituitary-ovarian axis
to androgen excess may trigger a series of events that
could determine PCOS onset of at puberty.
The source of intra-uterine androgens excess is un-
likely to be maternal, since the foetus is protected by
placental aromatase activity and by high maternal SHBG
concentrations.
The expression of aromatase in the placenta of PCOS
women may be diminished [9] and this could potentially
be unable to prevent foetal testosterone (T) excess in
PCOS pregnancies [10]. It has been seen that the preva-
lence of decreased aromatase required to carry out T
excess in female fetuses was reported to be extremely
rare [11]. On the other hand, recent studies on hyper-
tensive preeclamptic pregnancies have demonstrated a
significant reduction in placental ability to synthesize
oestrogens, indicating a gestational impairment of T
aromatization that is more common than was previously
considered [12, 13].
Thesourceofandrogensexcessismorelikelyto
be the foetal ovary, which is normally quiescent, but
it could produce an excess of androgens in response
to maternal hCG in subjects genetically predisposed
to PCOS.
In newborn daughters of PCOS women, elevated T
levels have been observed in the umbilical venous blood
[14, 15]. This finding was not confirmed in other studies
that demonstrated instead a reduced umbilical cord
blood androstenedione levels [9, 16]. Hichey et al.,
showed no increase in T levels in umbilical cord blood
of adolescent girls diagnosed with PCOS [17]. Taken the
ovary as a key foetal site for gestational T excess, during
critical mid-gestational age for target organ differenti-
ation [9], studies at the time of birth, are likely to be too
late to detect any remaining hormonal differences [18,
19]. The mid-gestational T excess in human female foe-
tuses can be accompanied by gestational hyperglycaemia
and foetal hyperinsulinemia. Interestingly, elevated mid-
gestation maternal T levels predict high AMH levels in
adolescent daughters [20]. Since elevated AMH repre-
sents a characteristic of adolescents and women with
PCOS [21] and daughters of PCOS women [22, 23], such
associations might suggest a cross-generational relation-
ship between the degree of maternal hyperandrogenism
and the development of PCOS in their daughters.
Complete manifestation of the syndrome occurs at
adolescence, when the hypothalamus-pituitary-ovarian
access is activated. At this time, metabolic changes lead-
ing to modifications in the distribution of body fat also
occur. In particular, at puberty there is a physiological
increase in insulin levels, determining on one hand a re-
duction in SHBG levels with amplification of the effects
of circulating androgens, and on the other hand, direct
stimulation of ovarian steroidogenesis [24]. In women
with PCOS, the physiologic hyperinsulinemia of adoles-
cence may be a triggering factor for the development of
hyperandrogenism and anovulation. Girls predisposed to
insulin-resistance and overweight are even more at risk
of developing early adrenarche and subsequent PCOS at
adolescence [24] (Fig. 1).
Daughters of women with PCOS evaluated during
early childhood (age 4–8 years) and early puberty (age
9–13 years) have exaggerated adrenarche compared with
daughters of non-PCOS women of similar pubertal stage
and body mass index (BMI) [25]. This is consistent with
a role of obesity-related insulin- resistance in causing
hyperandrogenemia in these girls through an effect of
insulin on adrenal and ovarian steroidogenesis [26],
manifesting as early adrenarche [27] and subsequent
PCOS [28]. Such hyperandrogenemia appears to modu-
late gonadotropin levels, as has been demonstrated in
obese peri-pubertal girls who were found to have in-
creased LH frequency but low LH amplitude, and dimin-
ished overnight LH pulse amplitude compared with
normal-weight girls [29]. These changes may reflect ini-
tial effect of obesity on LH pulses [30]. Subsequently,
hyperandrogenemia reduces the inhibition of GnRH
pulse frequency by progesterone, causing rapid LH pulse
secretion and further increase in ovarian androgen pro-
duction [30–32].
Epigenetics and PCOS
Since the development of other diseases in adulthood,
induced by nutritional or environmental factors in utero,
usually involves an epigenetic mechanism, it seems likely
that the same mechanism may also occur in PCOS.
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38 Page 2 of 17
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According to this hypothesis, exposure to hyperandro-
genism in utero may lead to epigenetic reprogramming
anomalies in foetal reproductive tissue, which is trans-
lated into the PCOS phenotype in adulthood. Moreover,
if such epigenetic alterations persist in the germ cell line,
transgenerational transmission of the PCOS phenotype
is promoted. Clearly other genetic factors (i.e. linked
to insulin resistance) and post-natal environmental
factors (i.e. diet) may contribute to the development
of PCOS phenotype, possibly in association with epi-
genetic anomalies.
In particular, epidemiologic and clinical studies con-
ducted largely in adult human populations suggest a link
between foetal growth restriction, and subsequent risk of
type 2 Diabetes Mellitus (DM) and cardiovascular dis-
ease [33, 34]. The increased risk for these metabolic dis-
eases has been linked to elevated insulin resistance in
young individuals exposed to an adverse in utero envir-
onment and born small for gestational age (SGA) [35,
36]. These studies support an overall relationship be-
tween foetal growth restriction and increased adiposity
and insulin resistance starting early in the childhood
period. In addition to the in utero environmental factors,
genetic polymorphisms may modulate insulin resistance
parameters in SGA individuals. This may partially ex-
plain the variable degree of insulin resistance in subjects
exposed to an adverse in utero environment [37]. At the
other extreme, over-nutrition of theses foetuses appears
to have long-term effects on obesity, insulin resistance,
and predisposition to disorders of glycemic regulation.
Offspring of mothers with diabetes during pregnancy
have a higher frequency of childhood obesity and earlier
onset of impaired glucose tolerance [38, 39] and type 2
DM [40]. Given the effect of insulin on modulating ovar-
ian [41] and adrenal [42] steroidogenesis, a role of intra-
uterine adverse events which lead to insulin resistance
and/or hyperinsulinemia may predispose adolescents to
PCOS. Overall, these studies indicate that at least some
metabolic components of the PCOS phenotype are pro-
grammed in utero, particularly the tendency for higher
fat mass, visceral adiposity, and insulin resistance.
If further research verifies this hypothesis, new pros-
pects for preventive treatment during the critical pre-
natal period will be mandatory.
Genetic factors
Increasing evidences over many years point to familial
aggregation of women with PCOS, hyperandrogenism
and metabolic alterations [43]. The model of inheritance
of PCOS has not yet been defined. Some researchers
have postulated autosomal dominant transmission linked
to a single genetic defect, but most authors define PCOS
as a polygenic pathology. It is also possible that a par-
ticular gene in a given family may have a predominant
effect, influencing the phenotypic manifestations of the
syndrome. The main candidate genes are those encoding
for factors involved in the synthesis, transport, regula-
tion and effects of androgens. Other candidate genes are
those encoding for factors involved in insulin metabol-
ism, such as insulin receptors, signalling cascade pro-
teins responsible for binding of insulin to its receptor,
IGF system, other growth factors and the gene encoding
Fig. 1 Theory of prenatal origin of PCOS and its development at puberty
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38 Page 3 of 17
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for Calpain-10 enzyme, responsible for insulin secretion
and action [43].
An association has also been found between “pro-
inflammatory”genotypes and PCOS, linked to poly-
morphism of genes coding for TNF-alfa, IL-6 and IL-
6 receptor [43]. Finally, recent evidence of altered
early gonadotropin-independent folliculogenesis in women
with PCOS suggests that genes involved in folliculogenesis
may also be candidates in the etiopathogenesis of this
syndrome [1].
However, only a few PCOS susceptibility genes have
been repeatedly identified in studies of women with
Chinese or European ancestry: allelic variants of fibrillin-
3 (FBN3) [44–47], and variants of LH receptor (LHR)
[44, 48, 49]. FBN3 encodes for an extracellular matrix
protein that regulates transforming growth factor (TGF)
signaling. Its PCOS associated allelic variant, A8, mani-
fests a metabolically distinct phenotype, including insu-
lin resistance [50]. FBN3 expression, is limited to early
to mid-gestation in many organs and tissues, including
the ovary [51, 52]. Such a gestational stage includes a
period of foetal developmental at which T exposure in-
duces altered DNA methylation of TGF-beta–regulating
genes and subsequent PCOS-like traits [53]. Due to the
degree and type of fibrillin expression contributes to dif-
ferences in elasticity of cell extracellular matrix interac-
tions and storage of TGF-beta, fibrillin may provide
gestationally relevant [51] tissue-specific bases for cell
mediated engagement of extracellular matrix–stored
TGF-beta in proliferation, differentiation, and apoptosis
[54, 55]. In the ovary, variants of LHR may diminish or
enhance pituitary LH stimulation of ovarian theca and
stroma cell T production, ovarian follicle development,
LH surge–induced ovulation, and corpus luteum func-
tion [56], while in adipocytes, LHR variants may alter
LH stimulation of adipogenesis [57]. Variants in these
multi-organ system genes could contribute to genetically
determination of PCOS phenotypes for reproductive and
metabolic pathophysiology.
Environmental factors
Although the prevalence of PCOS is similar in all coun-
tries, ethnic factors influence the phenotypic manifesta-
tions of the syndrome. The prevalence of PCOS among
Caucasian women, varies from 4.7 % in Alabama, to
6.5 % in Spain and 6.8 % in Greece [58]. In the United
Kingdom, PCOS and type II diabetes are more frequent
in women of Asian origin [58]. These observations sug-
gest the existence of different environmental factors,
such as diet, physical activity and life-style in general.
The increasing effects of metabolic disorders in eco-
nomically developed countries has led authors to suggest
that the pathogenic mechanisms of these disorders are
associated with evolutionary advantages in terms of
survival [58]. On one hand, insulin resistance increases
the availability of glucose for brain metabolism, while on
the other, it increases blood pressure by mechanisms
such as fluid retention and increase in the sympathetic
tone. It also induces modifications in clotting factors
(hypercoagulation) and a propensity for obesity charac-
terised by a proinflammatory condition with increased
secretion of cytokines and inflammatory factors. All the
aforementioned alterations make the subject more resist-
ant and favours survival when faced with stressors such
as reduced availability of food, wounds and epidemics.
The relative infertility of these women increases the
interval between pregnancies and reduces the number of
children, favouring survival of mothers and children. In
the absence of stressors, as in the case of developed
countries, these pathogenic mechanisms predispose to
cardiovascular disease and atherosclerosis.
Endocrine factors
Ovarian folliculogenesis is regulated by a delicate equi-
librium between extra- and intra-ovarian factors. Dis-
turbance of this equilibrium may alter and compromise
follicular development and the formation of mature oo-
cytes, leading to infertility (Fig. 2).
Extraovarian factors
Extraovarian factors include a series of endocrine,
paracrine and metabolic alterations, which by causing
abnormalities in the follicular microenvironment, may
alter folliculogenesis and oocyte development. These al-
terations include FSH deficit, hypersecretion of LH,
hyperandrogenemia of ovarian or adrenal origin and
hyperinsulinemia with insulin resistance [59]. Folliculo-
genesis and oogenesis also depend on intraovarian fac-
tors, especially follicular fluid factors (FFFs) [59] that are
directly correlated with their levels in plasma. Recent
studies suggest that FFFs implicated in folliculogenesis
of polycystic ovaries belong to the family of growth fac-
tors including cytokines and inhibins [59].
Vitamin D is an essential regulator of bone and min-
eral homeostasis. Recent studies have demonstrated
hypovitaminosis D is associated with an increased likeli-
hood of developing metabolic disorders. [60]. Vit.D defi-
ciency has also been demonstrated in patients with
POCS [61]. Obese patients with PCOS have been shown
to have lower serum levels of 25-OH-D than non obese
women with PCOS and vitamin D deficiency has been
suggested to have a role in the development of insulin
resistance (IR) and impaired glucose tolerance in such
patients [62]
Altered secretion of GnRH and gonadotropins
Although the etiopathogenesis of PCOS is still contro-
versial, series of hypotheses have been proposed in the
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recent decades. A high percentage (55–75 %) of women
with PCOS have an elevated LH/FSH ratio presumably
due to high levels of LH rather than reduced production
of FSH. GnRH stimulation causes, indeed, excessive LH
production [63] in those women. This condition may be
determined by a higher frequency or amplitude of GnRH
[60]. It is not yet clear whether alteration of the
hypothalamo-pituitary axis in PCOS is primary or sec-
ondary to alterations in steroid hormones secretion. The
role of FSH is to recruit ovarian follicles and stimulate
their growth: 2–5 mm follicles are sensitive to FSH,
whereas larger ones (6–8 mm) acquire aromatase
activity and may increase oestradiol (E2) and inhibin B,
reducing levels of FSH in late follicular stage. On the
other hand, PCOS patients (having LH and FSH concen-
trations higher and lower than normal, respectively)
accumulate antral follicles (2–8 mm) that differentiate
early and undergo premature growth arrest [63]. Hyper-
secretion of LH in these women may promote early
luteinisation of granulosa cells and contribute to early
growth arrest of antral follicles (Fig. 3). LH may also ac-
tivate premature meiotic processes that damage oocyte
quality and contribute to the formation of embryonic
aneuploidies [64].
Altered dopaminergic and opioid tone has also been
found in these patients. However, administration of
opioid antagonists or dopaminergic agonists in PCOS
patients have little influence on LH pulsatility [63].
Among the excitatory elements of the reproductive
axis, kisspeptins have recently emerged as essential up-
stream regulators of GnRH neurons, with indispensable
roles in key aspects of reproduction, such as brain sex
Fig. 2 Alteration of extra- and intra-ovarian factors may compromise follicular development and oocyte development in PCOS
Fig. 3 In a normal cycle, only the dominant follicle responds to LH when it reaches 10 mm diameter. In PCOS the response to LH occurs inappropriately
in smaller follicles and many antral follicles reach terminal differentiation before time, producing a greater quantity of steroids and inhibin B that exert
negative feedback on FSH production
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differentiation, puberty onset, gonadotropin secretion,
ovulation, and the metabolic regulation of fertility [64–
68]. Kisspeptins are a family of closely related peptides
of different amino acid length (such as Kp-54 and Kp-
10) that are encoded by the Kiss1 gene and operate
through the G protein–coupled receptor Gpr54, also
named kisspeptin receptor or Kiss1R [64, 65, 68]. Ex-
pression of the elements of the Kiss1 system in different
ovarian compartments has been documented in human
and rodent species [69, 70]. Ovarian expression of Kiss1
is under the positive control of gonadotropins [69]. On
the other hand, local mediators also participate in the
control of ovarian Kiss1 expression; inhibition of prosta-
glandin synthesis, which causes ovulatory dysfunction,
evokes a marked suppression of ovarian Kiss1 mRNA
levels during the periovulatory period. Moreover,
inhibition of prostaglandin synthesis blocks the positive
effect of gonadotropins on Kiss1 gene expression in the
ovary [70].
Taken as a whole, these observations suggest a poten-
tial role of locally produced kisspeptins in the control of
ovulation. Whether alterations of such local actions of
kisspeptins might contribute to the ovulatory dysfunc-
tion seen in PCOS warrants specific investigation.
Ovarian and extraovarian hyperandrogenism
Hyperandrogenemia is the most typical hormonal alter-
ation of PCOS. Biochemically, hyperandrogenism is
usually assessed by assay of total testosterone (TT), free
testosterone (fT), sex hormone binding globulin (SHBG),
androstenedione (A), 17-hydroxy progesterone (17-
OHP) and dehydroepiandrosterone sulphate (DHEAS)
in serum and by calculation of the free androgen index
(FAI = (TT/SHBG)100). Women with PCOS often have
higher than normal serum concentrations of all these
androgens. Hyperandrogenism has a multifactorial origin
attributed mostly to the ovaries with a substantial contri-
bution from the adrenals and a minor contribution from
fatty tissue.
Biosynthesis of androgens is mediated by microsomal
P450c17 which catalyses 17–20 lyase activity. Alterations
in P450c17 at transcriptional and post-transcriptional
level have been implicated in the aetiology of PCOS
[71]. These women show, indeed, relative inhibition of
17–20 lyase activity with respect to 17-hyroxylase, lead-
ing to an increased 17OHP/A ratio. Administration of
GnRH or hCG in women with PCOS causes excessive
production of 17OHP [68]. Low aromatase activity has
also been demonstrated in women with PCOS. Aroma-
tase is a granulosa cell enzyme that converts androgens
into estrogens. It may be partly responsible for hyperan-
drogenism in this syndrome [70, 71] (Fig. 4).
Elevated levels of androgens may have a negative
impact on follicular development, causing atresia, and
on ovarian development, inhibiting meiotic matur-
ation by decreasing oscillations of intracytoplasmic
calcium levels [59].
Hyperinsulinemia and insulin resistance
Insulin resistance is defined as a pathological condition
in which a cell, tissue or organism requires above-
normal quantities of insulin to respond normally. It
causes increased insulin secretion by pancreatic βcells
and compensatory hyperinsulinemia, while blood glu-
cose remains normal. When the response of pancreatic
cells decreases, the patient develops glucose intolerance
or type II diabetes [5].
Fig. 4 Relative inhibition of 17–20 lyase activity with respect to 17-hydroxylase has been found in women with PCOS. This leads to an increase in
the 17OHP/A ratio and reduction of aromatase activity, the enzyme of granulosa cells that converts androgens into estrogens
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38 Page 6 of 17
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Since many women with PCOS seem to have insulin
resistance, compensatory hyperinsulinemia is thought to
contribute to hyperandrogenism [72, 73] by direct
stimulation of ovarian production of androgens and by
inhibition of liver synthesis of SHGB that increases tes-
tosterone availability. Insulin also increases ACTH-
mediated adrenal androgen production and accentuates
LH-stimulated ovarian steroidogenesis [73] (Fig. 5).
About 60–70 % of women with PCOS are obese or
overweight, and obesity is associated with insulin resist-
ance. However, many studies have shown that insulin re-
sistance is also present in many lean women with PCOS
[5, 73]. The mechanisms leading to insulin resistance
consist of a defect in insulin binding to its receptor or to
changes in insulin signal transmission [5, 74]. However,
the ovaries of these women maintain approximately a
normal response to insulin. A partial elucidation of this
mechanism is explained by the action of insulin on the
ovary through the IGF-1 receptor. This binding occurs
when insulin reaches high concentrations, as compensa-
tory hyperinsulinemia. Moreover, the action of insulin
on the ovary uses the inositol glycan system as a signal
mediator, a different mechanism from the system
activated by phosphorylation of the receptor at tyrosine
level in other tissues [75]. An increase was observed in
urinary clearance of inositol in some American and
Greek women with PCOS. It reduces tissue availability
of inositol. This mechanism could contribute to insulin
resistance present in PCOS women [76]. Hyperinsuline-
mia directly stimulates ovarian steroidogenesis by acting
on thecal and granulosa cells. In vitro studies have dem-
onstrated that insulin stimulates thecal cell proliferation,
increases secretion of androgens mediated by LH and in-
creases cytochrome P450 expression of LH and IGF-1
receptor. Since the enzymes involved in ovarian ste-
roidogenesis are similar to those of the adrenals, many
studies have shown that insulin may act directly as
stimulator adrenal steroidogenesis [5, 73]. The adminis-
tration of metformin, an insulin-sensitising drug, signifi-
cantly reduces production of 17OHP, T and A in
response to ACTH in PCOS women [5].
In vitro data, obtained with cell culture models, indi-
cate that co-incubation of insulin and FSH with bovine
oocytes promotes up-regulation of LH receptors on
granulosa cells of antral follicles. It contributes to arrest
of follicular growth, inhibits of aromatase activity, and
Fig. 5 Hyperinsulinemia stimulates directly cytochrome p450 enzymes in the ovary or indirectly through action of LH or IGF-1,
causing hyperandrogenism
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potentially triggers to ovarian hyperandrogenism. Look-
ing at the molecular level, insulin binds to its receptor
on granulosa and thecal cells and on oocytes where it
may alter expression of certain genes involved in the
meiotic process of the oocyte [59].
In vitro studies have demonstrated that insulin also has
receptors at hypothalamus and pituitary levels, through
which it stimulates the release of FSH and LH under basal
conditions and after GnRH stimulation [5, 59].
Furthermore, insulin also influences hyperandrogen-
ism by inhibiting liver synthesis of SHBG
2
and IGFBP-1,
which binds IGF-1 [5, 59] IGF-1 is a growth factor with
endocrine action. It is mainly synthetized by the liver,
but is also produced by other tissues, including the ovar-
ies, where it has autocrine/paracrine functions. Many
studies have shown a significant increase in the IGF-1/
IGFBP-1 ratio in women with PCOS. An increased
availability of IGF-1 in thecal cells can induce increased
production of androgens. Moreover, IGF-1 stimulates
oestrogen production by granulosa cells and synergically
acts with FSH and LH in modulating expression of aro-
matase in granulosa cells. IGF-1, like insulin, also exerts
an indirect control on ovarian steroidogenesis through
the hypothalamus-pituitary axis. It induces, in fact,
expression of GnRH and release of gonadotropins by the
pituitary [5, 59]. Treatment with insulin-sensitising
drugs increases IGFBP-1 levels, reduces the IGF-1/
IGFBP-1 ratio and decreases IGF-1 availability in periph-
eral tissues [77].
Intra and extra-ovarian factors
Epidermal growth factors (EGF)
Epidermal growth factor (EGF) plays an important role
in regulation of cell growth, as well as in proliferation
and differentiation through interaction with its receptor
EGFR (ErbB1, ErbB2-4) [59, 71]. In the human ovary,
EGF is present in follicular fluid (FF), where it regulates
follicle development and oocyte maturation. In women
with PCOS, FF EGF levels are higher than in normal
ovulating women. In PCOS condition, EGF may inhibit
granulosa cell oestrogen synthesis, which is translated
into arrest of follicle growth [59, 71].
Insulin-like growth factors (IGF)
These growth factors are multifunctional polypeptides
with insulin-like activity that play important regulatory
functions for follicle and oocyte development [59, 71,
78]. Circulating IGFs are produced by the liver: IGF-1 is
secreted by thecal cells, whereas IGF-2 is synthesised by
granulosa cells and IGFBP (insulin-like growth factor
binding protein) has been found in FF and is expressed
by granulosa and thecal cells [78]. FF IGF-1 levels in
PCOS women are elevated than in normal women,
whereas IGFBP-1 are lower in PCOS patients, causing
the arrest follicle growth [78].
Neurotrophin growth factor (NGF)
NGF is not only involved in development of the nervous
system but also acts in the ovaries of humans and other
mammals. It plays a fundamental role in folliculogenesis
and oocyte maturation [59, 71, 78]. This factor promotes
nuclear and cytoplasmic maturation of oocytes, and pro-
cesses essential for the development of good quality oo-
cytes and embryos. Elevated NGF concentrations in FF
have been reported in women with PCOS [59, 71, 78]
Transforming growth factor-b (TGF-beta)
Members of the TGF-beta family play a role in follicle
growth and oocyte development. They include anti-
mullerian hormone, activin, follistatin, inhibins, bone
morphogenetic protein (BMP)-9 and growth and differ-
entiation factor (GDF)-9 [78, 79]. In different occasions,
these growth factors may promote or block follicle
growth and/or differentiation [74, 80].
Anti-Mullerian hormone (AMH)
AMH is a homodimeric glycoprotein that inhibits the
development of Mullerian ducts in male embryos [59]. It
is expressed by granulosa cells in the ovaries of women
of reproductive age, where it controls the formation of
primary follicles and follicle recruitment by FSH. There-
fore playing an important role in folliculogenesis [74, 78,
79]. Women with PCOS have higher serum and FF con-
centrations of AMH compared to controls. This is
closely correlated with greater development of antral fol-
licles and arrest of follicular growth [79, 80]. High serum
levels of AMH are directly correlated with an increase in
testosterone and/or LH concentrations in women with
PCOS, as well as with altered oocyte maturation and low
embryo quality [64, 80]. Furthermore, elevated concen-
trations of AMH in FF of women with PCOS are corre-
lated with a higher percentage of immature oocytes and
lower fertilisation rates compared to women with endo-
metriosis or pelvic adhesion syndrome [80].
Activin, follistatin and inhibin
Activin, follistatin (FS) and inhibin are polypeptides,
which were originally isolated from ovarian FF. FS is a
binding protein produced by ovarian granulosa cells;
cellular growth and differentiation is regulated by auto-
crine/paracrine action. Over-expression of FS has been
associated with arrest of follicle growth and reduced
oocyte development. Activin is mostly secreted by
smaller follicles. It promotes follicle development by in-
creasing granulosa cell response to FSH stimulation; it
decreases androgen synthesis and stimulating oocyte
maturation. Besides inhibiting FSH production, inhibins
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38 Page 8 of 17
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are produced by the dominant follicle and stimulate the-
cal cells to produce androgens as substrate for estrogen
formation [59, 74, 78, 79]. An increased FS/activin ratio
and elevated concentrations of inhibin B have been
found in PCOS [59, 74, 78, 79].
Vascular endothelial growth factor (VEGF)
VEGF is a homodimeric glycoprotein expressed in gran-
ulosa and thecal cells [78] and also present in FF [59]. It
plays an important role in angiogenesis, follicular vascu-
larisation and intra-follicular oxygenation. It has there-
fore an impact of follicle maturation, oocyte quality,
fertilisation and embryo development [59, 74, 78, 79].
The alterations in FF concentrations of VEGF in patients
with PCOS is indicative of oocyte immaturity [78]. The
elevated concentrations are useful as an indicator of
oocyte maturity, successful fertilisation and embryo
development in women with PCOS [78].
Interleukins (IL)
Interleukins are a group of cytokines produced by
leukocytes. In particular, IL-1, IL-2, IL-6, IL-8, IL-11
and IL-12 play different roles in the regulation of fol-
liculogenesis, ovulation and corpus luteum function.
Concentrations of IL-12 in FF differ from immature
follicles and those in pre-ovulatory phase [78], and re-
duced FF concentrations of IL-12 and elevated FF
concentrations of IL-13 in patients with PCOS are
correlated with reduced oocyte maturation, fertilisa-
tion and pregnancy [59, 74, 78, 79].
Tumour necrosis factor α(TNF-α)
TNF-αis involved in the regulation of ovarian function,
exerting an influence on proliferation, differentiation,
follicle maturation, steroidogenesis and apoptosis. TNF-
αis expressed by the oocyte, thecal cells, granulosa cells
and the corpus luteum in the ovary. Alterations in TNF-
αlevels in FF are correlated to poor oocyte quality. In-
creased FF concentrations of TNF-αin women with
PCOS are also significantly inverse correlated to FF con-
centrations of E2, which are indicative of poor oocyte
and embryo quality [78].
Fas and Fas ligand (FasL)
Fas and FasL are membrane proteins belonging to a
TNF subfamily, and they respectively have anti- and
pro-apoptotic functions. Concentrations of Fas in FF are
positively correlated with oocyte maturity [78]. In
women with PCOS treated with metformin, a reduction
in FF concentrations of FasL has been reported, with a
consequent increase in implant and pregnancy percent-
ages [59, 74, 78, 79].
Biomolecules related to carbohydrate metabolism
Proteomic studies show modulation of several proteins
related to the carbohydrate metabolism. The abundance
of many proteins such as aconitate hydratase, fructose
bisphosphate aldolase A, malate dehydrogenase, isoen-
zymes M1/M2 of pyruvate kinase, and transaldolase has
been found to be increased in ovarian tissue and in
ovarian granulosa cells from PCOS patients. Instead,
UDP-glucose 6-dehydrogenase protein was reduced in
PCOS women.
Moreover, triosephosphate isomerise was shown to
have increased gene expression in ovarian tissue from
PCOS patients.
Biomolecules related to lipid metabolism
Women with PCOS frequently present an atherogenic
serum lipid profile consisting of increased triglycerides,
cholesterol, low-density lipoprotein cholesterol concen-
trations and reduced apolipoprotein A-I levels. Insulin
resistance, androgen excess and obesity may all contrib-
ute to the abnormalities of lipid metabolism observed in
women with PCOS.
Apolipoprotein A-1 (ApoA-I), the major structural pro-
tein component of HDL-cholesterol particles, has several
pleiotropic biological functions: promotion of macrophage
cholesterol efflux, stimulation of reverse lipid transport,
inhibition of LDL oxidation, removal of toxic phospho-
lipids and also many other anti-inflammatory properties.
Proteomic techniques found a decreased abundance of
ApoA-I in visceral adipose tissue and in whole ovarian
tissue from women with PCOS [80–82]. Moreover, re-
duced ApoA-I abundance in granulosa cells from these
women may influence the expression of steroidogenic
enzymes and the production of the steroid hormone
progesterone [83].
Apolipoprotein C-I (ApoC-I) inhibits lipoprotein me-
tabolism in the liver. Several authors showed, thus, in-
creased serum ApoC-I levels in women with PCOS
compared to normal controls, especially in those pre-
senting with insulin resistance [84].
Adipocyte plasma membrane-associated protein
(APMAP) may represent a novel member of paraox-
onases [85], which are known to be involved in anti-
oxidant processes. Lower level of APMAP has been
found in visceral adipose tissue in patients with
PCOS [81] might contribute to the impairment in
antioxidant defense characteristic of PCOS [86].
Biomolecules related to protein metabolism
Proteomic techniques indicated that ovarian tissue (in
patients with PCOS) presents high levels of proteins
involved in the metabolism of amino acids, in post-
translational protein modification and in protein deg-
radation [82].
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Methionine adenosyltransferase II (MAT2B), an en-
zyme involved in the removal of homocystein, is de-
creased in the PCOS ovary [82]. Moreover, cathepsin D,
an acid protease involved in intracellular protein
breakdown implied in the pathogenesis of several dis-
eases, such as, breast cancer [87, 88]; it is decreased in T
lymphocytes from women with PCOS. The biological
significance of this decrease is not clear [89].
Other factors
Heat shock proteins (HSPs)
Heat shock proteins (HSPs) are a highly conserved fam-
ily of molecules involved in protein folding. Many com-
ponents of survival and apoptotic pathways are
regulated by molecular chaperones such as heat shock
proteins [90]. The decrease at the protein level of
Hsp10, Hsp27 and Hsp60 in ovarian tissue and granu-
losa cells from patients with PCOS [79, 80] might
contribute to apoptosis within the ovarian follicle. In ac-
cordance, Hsp60 is down-regulated in adipose tissue in
PCOS gene expression studies [91].
Transferrin
Transferrin is the major iron transporter in the circula-
tion and it is increased in PCOS women. High levels of
trasferrin may not be related to inflammation but repre-
sent a compensatory mechanism against the limitation
of iron availability for erythropoiesis characteristic of
chronic disorders [92]. Similarly, the decrease in α2
macroglobulin observed in patients with PCOS might be
related to the increased body iron stores, observed in
these women [93, 94].
Homocysteine
Homocysteine (Hcy) is a homologue of the amino acid
cysteine and may be converted into methionine or cyst-
eine in the presence of B-complex vitamins. Many stud-
ies have shown that elevated Hcy levels in serum and FF
are inversely proportional to oocyte and embryo quality
[59, 74, 78, 79]. High FF and serum concentrations of
Hcy may suppress E2 synthesis and therefore interfere
with follicle growth and oocyte maturation in women
with PCOS [59, 74, 78, 79].
Leptin
Leptin is a protein hormone that plays a key role in
regulating energy supply and demand. High FF and
serum concentrations of leptin are closely associated
with a decrease in oocyte maturity and embryo quality
in patients with PCOS. Certain studies have also demon-
strated that high levels of leptin in women with PCOS
play a role in PCOS pathogenesis, acting by inhibiting
E2 production and interfering with follicle development
and oocyte maturation. On the other hand, some
authors have demonstrated that leptin is reduced in FF
of women with PCOS and is therefore not a useful
marker for evaluating oocyte quality [59, 74, 78, 79]. In-
depth research is therefore needed to elucidate the role
of leptin in the pathophysiology of PCOS.
Oxidative stress (OS)
Oxygen free radicals or reactive oxygen species (ROS)
are involved in many physiological functions where they
act as mediators in a variety of signal transduction path-
ways [59]. An excess of these substances can cause cellu-
lar damage. In women with PCOS, elevated levels of
ROS in FF and reduced antioxidant capacity are closely
associated with reduced oocyte maturation and low em-
bryo quality [59, 74, 78, 79]. These molecules may re-
duce oocyte quality by altering the equilibrium of FFFs
in the follicular microenvironment.
The decrease in mitochondrial O2 consumption and
glutathione (GSH) levels, along with increased ROS pro-
duction, explains the observed mitochondrial dysfunc-
tion in PCOS patients [95]. The mononuclear cells of
women with PCOS are increased in this inflammatory
state [96], which occurs more often in response to
hyperglycemia and C-reactive protein (CRP). Physio-
logical hyperglycemia generates increased levels of ROS
from mononuclear cells, which then activate the release
of TNF-αand increase inflammatory transcription factor
NF-kappa B. As a result, the concentrations of TNF-α,a
known mediator of insulin resistance, are further in-
creased. The resulting OS creates an inflammatory envir-
onment that promotes insulin resistance and contributes
to hyperandrogenism [97].
Clinical manifestations
The typical clinical indications of PCOS are: anovulatory
cycles, ultrasonographic evidence of polycystic ovaries
and hirsutism. Many women are also overweight or
obese and have an increased risk of developing meta-
bolic syndromes in later life. During pregnancy, there is
a higher chance of miscarriage, gestational diabetes and
hypertension.
Anovulatory cycles
Anovulatory cycles often manifest with oligoamenorrhea,
secondary amenorrhea or abnormal uterine bleeding.
The term oligomenorrhea refers to cycles of more than
35 days, while secondary amenorrhea is an absence of
menstruation for more than three months. Polymenor-
rhea condition, meaning more frequent cycles, generally
with an interval of less than 24 days, may occur in a mi-
nority of cases. Since regular cycles do not exclude
chronic anovulation, it is necessary to measure serum
concentrations of progesterone in luteal phase of the
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cycle (days 20–24). If they are below 5 ng/mL, the cycle
is probably anovulatory.
Menstrual irregularities often begin after menarche
and decrease when the patient approaches menopause
[98]. This correlated to a decline in androgen levels with
advancing age in women with PCOS [98]. While evaluat-
ing the length of the menstrual cycle, it should be
recalled that oligo-anovulation is quite common in ado-
lescents, especially in the first year after menarche. Set-
tling into regular cycles may be a slow process, which, in
some cases, may take three years after the first period.
This is why it is important to be cautious in diagnosing
and treating PCOS in adolescents. The incidence of ir-
regular cycles in adolescents with PCOS seems to vary
significantly: about 43 % with oligomenorrhea, 21 % with
primary or secondary amenorrhea, 21 % with regular
menstrual cycles and 7 % with polymenorrhea [99]. 95 %
of adult women with PCOS have amenorrhea [5, 99].
Ultrasonographic features of the ovaries
The Rotterdam guidelines of 2003 include ultrasono-
graphic evidence of polycystic ovaries as a criterion for
the diagnosis of PCOS. This finding is not exclusive
because young healthy women may have ovaries with
polycystic features. Polycystic ovaries may also be ob-
served during pubertal development in patients with
hypothalamic amenorrhea and hyperprolactinemia [100].
The diagnostic criteria of PCOS are based on the pres-
ence of 12 or more follicles of diameter 2–9mmoran
ovarian volume of more than 10 mL in follicular phase.
Another feature is an increase in stromal tissue. These
morphological changes in the ovary may be encountered
in more than 80 % of women with a clinical diagnosis of
PCOS [100].
Hirsutism
Hyperandrogenism may manifest with hirsutism, acne
and alopecia. Hirsutism is the presence of terminal hair
on the face and/or body in a masculine pattern. It is the
most common symptom, found in about 60 % of women
with PCOS and it widely varies according to the ethni-
city. For this reason, the threshold of hirsutism should
be set considering the patient ethnicity. The most widely
used method to determine the degree of hirsutism is the
Ferriman-Gallwey score [101] which gives a score of 0 in
the absence of terminal hair in a given area of the body,
and a score of 4 for extensive hair growth. Hair is scored
in 9 different areas of the body, such as, chin, upper lip,
periareolar and intermammary areas, upper and lower
back, upper and lower abdomen, upper and lower limbs.
The score from each area is summed to obtain a final
score used for diagnosis. A score of 7 is indicative of
hirsutism. It is defined as “slight”for scores of 7–9,
“moderate”for 10–14 and “severe”for scores ≥15 [101].
Hirsutism may be simultaneously due to androgen
production, increased circulating levels of free tes-
tosterone (Ft) in women with PCOS; together with
an increased activity of androgens in the piloseba-
ceous units through action of 5-αreductase, an en-
zyme that transforms testosterone into the more
active dihydrotestosterone.
Acne
Acne occurs in 12–14 % of women with PCOS and var-
ies according to ethnicity: the highest reported incidence
regards Indo-Asian women and lowest, Pacific islanders
[102]. Acne consists of comedones, due to accumulation
of sebum and epithelial cell debris, which is colonised by
the bacterium Propionibacterium acnes. Inflammation of
the comedones leads to the formation of papules,
pustules and nodules. Androgens may exacerbate this
process, increasing sebum production by pilosebaceous
units. About 50 % of women with acne have no clinical
or biochemical evidence of hyperandrogenism. More-
over, many hirsute women with PCOS do not have acne.
These differences may be due to different peripheral
sensitivity of androgen receptors [102].
Alopecia
Alopecia consists in progressive hair loss or thinning.
The intensity varies from subject to subject. Androgenic
alopecia is often accompanied by seborrhea and dan-
druff. Sensitivity of the pilosebaceous unit to andro-
gens is highly variable and there is little correlation
between clinical features and biochemical profiles of
hyperandrogenism [102]. Hair loss in PCOS usually
involves thinning at the vertex with maintenance of
the frontal hairline.
PCOS in adolescence and at menopause
It has been known for several years that PCOS patients
have higher risk for a certain range of diseases compared
to the general population. This risk exposes them to
high morbidity and it is associated with high social im-
pact, both economic and in healthcare. These patholo-
gies include type II diabetes, metabolic syndrome,
cardiovascular disease, endometrial carcinoma and many
gestational complications. The clinical indicators of
hyperandrogenism are another important aspect for ado-
lescents with PCOS, considering of self-perception in
this delicate period of life, when physical appearance is
fundamental for self-acceptance and relationships with
others. Hirsutism, acne and obesity cause psychological
distress that may develop into personality disorders and
depression. Early diagnosis and treatment of PCOS in
adolescence is therefore fundamental because it can slow
down or prevent the appearance of these pathologies in
adulthood. Diagnosis of PCOS in adolescence is more
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problematical than in adulthood and, according to some
authors, should be based on all three Rotterdam criteria
[103]. Oligomenorrhea should have a history of at least
two years since menarche and diagnosis of polycystic
ovary by abdominal ultrasonography should only be
based on increased ovarian diameter (>10 cm
3
). If diag-
nosis cannot be confirmed patients should be carefully
monitored until adulthood, and if symptoms persist the
diagnosis should be reassessed [103].
The clinical manifestations of PCOS in perimenopause
period are not well known. There is histological evidence
that women with PCOS have a larger cohort of primary
follicles than healthy women of the same age, a greater
number of antral follicles detectable by ultrasonography
and higher serum concentrations of AMH [104]. These
results suggest prolonged reproductive function and
greater ovarian reserves. Women with PCOS also seem
to achieve better menstrual regularity and probability of
ovulation with age (despite lower pregnancy rates). A
study of a prospective cohort of women during meno-
pause shows that those with PCOS go into menopause
an average of two years later than controls [104].
Long-term sequelae
Insulin resistance in young healthy women raises the
problem of other risk factors such as impaired glucose
tolerance (IGT), diabetes, hyperlipidemia, hypertension,
abdominal obesity and risk of cardiovascular disease [5,
105]. Since PCOS patients tend to have abdominal fat
deposition and insulin resistance, it has been suggested
that they may also have other metabolic alterations typ-
ical of so-called metabolic syndrome. This syndrome is
characterised by a series of symptoms, such as insulin
resistance, obesity, hypertension and hyperlipidemia.
Women with PCOS have elevated blood pressure, serum
triglycerides, LDL, total cholesterol and lower HDL
cholesterol than age-matched controls [5, 105]. Fur-
thermore, PCOS patients have a seven times higher
risk of myocardial infarction than controls of the
same age (Fig. 6).
Insulin resistance is recognised as a major risk factor
for type II diabetes [5, 105]. Factors such as obesity and
family history of type II diabetes can increase the risk of
diabetes in PCOS. About 30 % of obese women with
PCOS have IGT. A retrospective study by Dahlgren et
al. showed that prevalence of non-insulin-dependent dia-
betes mellitus (NIDDM) was 15 % in PCOS patients and
2 % in controls. Dunaif et al. [5, 105] suggested that up
to 20 % of PCOS patients have IGT or NIDDM in the
third decade.
It cannot be argued that PCOS patients with excess of
androgens and anovulation are more vulnerable to meta-
bolic dysfunction than other women. Women with
PCOS and anovulation, but with normal levels andro-
gens, and those with hyperandrogenism but regular
cycles, usually have normal insulin sensitivity and pre-
sumably do not have the same risk of IGT or type II
diabetes as those with the “classical phenotype”of the
syndrome [106].
Besides, women with PCOS are also at higher risk for
endometrial hyperplasia and carcinoma. This risk is, in
fact, influenced by various factors, such as obesity,
hyperandrogenism and infertility. All these factors can
be present in women with PCOS. A recent prospective
study of 56 PCOS patients showed a high prevalence of
endometrial hyperplasia [5, 105]. An interesting recent
review and meta-analysis confirms that women of all
ages with PCOS have an increased risk of endometrial
cancer but the risk of ovarian and breast cancer was not
significantly increased [107]. For this reason, preventive
Fig. 6 Insulin resistance is the link between PCOS and metabolic syndrome
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38 Page 12 of 17
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measures on PCOS patients for endometrial carcinoma
are suggested. These include recognition and treatment
of relative hyperestrogenism by periodic administration
of progesterone and/or ultrasonography and endometrial
biopsy in cases of long periods of amenorrhea. In any
case, at least four episodes of suspension bleeding per
year (every 3 months) are recommended.
PCOS and pregnancy: gestational complications
Women with PCOS show higher risk of gestational com-
plications, such as miscarriage, gestational diabetes,
hypertension and pre-eclampsia. These problems expose
them to a higher risk of premature delivery and caesar-
ean section [108]. Recent epigenetic theories suggest that
during PCOS pregnancy the embryo is exposed to an ex-
cess androgens that disrupts functional reprogramming
of foetal tissues [109, 110]. Maternal, placental or foetal
hyperandrogenism can distressed epigenetic reprogram-
ming of tissues, especially of genes regulating reproduction
and metabolism. Which can contribute to diseases such as
type II diabetes, hypertension, autism
31–32
and PCOS.
Epigenetic alterations of the androgen receptor gene on
chromosome X have, indeed, beenobservedinwomenwith
PCOS. However, a recent study failed to find any significant
differences in overall methylation of peripheral leukocyte
DNA between women with PCOS and matched controls
[109, 110], so aforementioned theory has not yet been
confirmed.
Women with PCOS have a 30–50 % of risk of miscar-
riage, which is three times higher than normal women
[111]. The mechanisms probably involved in the patho-
genesis of miscarriage in these women are:
1. overexpression of androgen and steroid receptors
and simultaneous reduced expression of molecules
of implantation, such as αvs β3integrinand
glycodelin [111];
2. hyperinsulinemia which inhibits endometrial and
stromal differentiation in vitro (decidualisation) and
locally down-regulates IGFBP-1 [111];
3. hypofibrinolysis mediated by high levels of
plasminogen activator inhibitor (PAI) [111];
4. increased resistance of the uterine arteries blood
flow leading to reduced sub-endometrial and endo-
metrial vascularisation [111] (Fig. 7).
Moreover, women with PCOS have a higher incidence
of gestational diabetes (20–30 %) and pre-eclampsia/
pregnancy-induced hypertension (PE/PIH) (10–15 %)
[108]. These alterations could be caused by obesity, al-
terations in glucose metabolism or in uterine vascular-
isation [112]. Obesity in pregnancy is, in fact, associated
with various complications, such as miscarriage, pre-
eclampsia, gestational diabetes, foetal macrosomia and
caesarean section [112]. Fat tissue produces adipokines,
including leptin, adiponectin, TNF-α, IL-6, resistin and
visfatin, which could be involved in activation of insulin
resistance in pregnancy. Adipokines can also produce an
excessive local and systemic inflammatory reaction,
which would play a key role in the pathophysiology of
PE/PIH and the birth of SGA babies. It is also possible
that placental macrophages contribute to inflammation
within the placenta by secretion of pro-inflammatory cy-
tokines such as IL-1, TNF-αand IL-6 in cytotrophoblast
and syncytiotrophoblast cells [112].
Glucose intolerance and insulin resistance are elevated
in women with PCOS even before pregnancy. Since
pregnancy causes physiological insulin resistance through
the action of placental hormones such as placental
lactogen (hPL), placental growth hormone (hPGH) and
Fig. 7 Factors involved in the etiopathogenesis of miscarriage in women with PCOS
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38 Page 13 of 17
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progesterone, women with PCOS have even an higher risk
of developing gestational diabetes. However, studies on
the prevalence of gestational diabetes in women with
PCOS show conflicting results that reflect the heterogen-
eity of the syndrome and the diversity of methods used to
diagnose gestational diabetes [108].
Furthermore, alterations of uterine vascularisation
reported in these women can determine reduced tropho-
blastic invasion leading to increased incidence of hyper-
tension and delivery of SGA babies [112].
Maternal and placental hyperandrogenism may con-
tribute to an increased risk of PE/PIH. In normal condi-
tion, the androgens synthesised by the placenta are
rapidly converted to oestrogens by placental aromatase.
Insulin inhibits placental aromatase and stimulates 3
βHDS activity. Expression of androgen receptors is sig-
nificantly increased in the placentas of women with PE/
PIH and this may induce vasoconstriction and throm-
bosis [108, 112]. Finally, all these complications expose
pregnant women with PCOS to a greater risk of prema-
ture delivery and caesarean section [108].
Outcome of newborns of mothers with PCOS
A meta-analysis aimed at evaluating neonatal complica-
tions in women with PCOS was recently conducted
[108]. The newborns of PCOS patients had a signifi-
cantly elevated risk of admission to the neonatal inten-
sive care unit and a higher possibility of perinatal
mortality [108]. Access to neonatal intensive care is
partially linked to premature delivery, which causes
hypoglycemia, jaundice and respiratory distress. Many
women with PCOS also undergo ovulation induction
and in vitro fertilisation and are therefore at chance for
multiple pregnancies [113]. Multiple pregnancy is an-
other major cause of increased perinatal morbidity.
However, the studies aforementioned did not show any
difference in multiple pregnancy between women with
PCOS and healthy women [113].
Given the excessive rate of gestational diabetes in
women with PCOS, an increased incidence of foetal
macrosomia could be expected. However, newborns of
women with PCOS show a significantly lower birth weight
than controls, although the size of this difference (mean
40 g) is probably of limited clinical significance [108].
The foetus of PCOS mothers is exposed to greater glu-
cose load, but placental distress can reduce the manifest-
ation of macrosomia. The association of PCOS and PE/
PIH suggests placental distress, especially in cases of pre-
term delivery [108]. The above-mentioned meta-analysis
had some limitations regarding heterogeneity of PCOS pa-
tients enrolled in the different studies. BMI, medically
assisted procreation and smoking during pregnancy were
not always considered, all of which are factors that may
affect obstetric and neonatal outcome [108].
Conclusions
PCOS is not only a reproductive pathology but also a
systemic condition and its etiopathogenesis is still not
completely understood. Recently, the approach of clin-
ical practice has been a progressive changed and im-
proved towards prevention together with the standard
treatments for diseases. Therapeutic tools are repre-
sented by hormonal contraceptives, antiandrogen drugs,
metformin and inositols
In this context, PCOS is an excellent example of path-
ology in whih early diagnosis and treatment can prevent
or delay its typical long-term sequelae.
In the past, therapy for PCOS has been centred on
treatment of hirsutism and restoration of ovulation.
However, it should be taken more into account the ob-
servation of hyperinsulinemia and insulin resistance,
which are often implicated in the pathogenesis of the
syndrome. Due to the fact that these alterations have
major repercussions on health in the long period, the re-
searchers should evaluate more appropriate strategies
for control of the metabolic alterations of PCOS.
Abbreviations
17-OHP, 17-hydroxy progesterone; A, androstenedione; AES, androgen
excess society; AMH, anti-mullerian hormone; APMAP, Adipocyte plasma
membrane-associated protein; ApoA-I, apolipoprotein A-I; BMI, body mass
index; BMP, bone morphogenetic protein; CRP C, reactive protein; DHEAS,
dehydroepiandrosterone sulphate; DM, diabetes mellitus; E2, oestradiol; EGF,
epidermal growth factor; FAI, free androgen index; FasL, fas and fas ligand;
FBN3, fibrillin-3; FF, follicular fluid; FFFs, follicular fluid factors; FS, follistatin;
FSH, follicle stimulating hormone; Ft, free testosterone; GDF, growth and dif-
ferentiation factor; GSH, glutathione; Hcy, homocysteine; HOMA, Homeostatic
model assessment; Hpgh, placental growth hormone; hPL, placental lacto-
gen; HSPs, heat shock proteins; IGF, insulin like growth factor; IGT, impaired
glucose tolerance; IL, interleukin; IR, insulin resistance; KP, kisspeptin; LH, lu-
teinising hormone; LHR, LH receptor; MAT2B, Methionine adenosyltransferase
II; NGF, neurotrophin growth factor; NIDDM, non-insulin-dependent diabetes
mellitus; NIH, National Institutes of Health; OS, oxidative stress; PCOS, policy-
ctyc ovary syndrome; PE/PIH, pre-eclampsia/pregnancy-induced hyperten-
sion; ROS, reactive oxygen species; SGA, small for gestational age; SHBG, sex
hormone-binding globulin; T, testosterone; TGF, transforming grow factor;
TGF-beta, Trasforming growth factor beta; TNF-α, tumor necrosis factor α; TT,
total testosterone; VEGF, vascular endothelial growth factor
Acknowledgments
The authors thank B. De Leo for assistance in language corrections and C.
Fiorini for data collection.
Funding
This research did not receive any specific grant from any funding agency in
the public, commercial or not-for-profit sector.
Availability of data and material
Not applicable.
Competing interests
The authors declare that they have no competing interests
Authors’contribution
Conception and design of the review: VDL, GM; write the article and collect
the references: MCM, VC, MGM; final approval of the version to be
submitted: FP. All authors read and approved the final version of the
manuscript.
De Leo et al. Reproductive Biology and Endocrinology (2016) 14:38 Page 14 of 17
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Consent for publication
Not applicable.
Ethics approval and consent to participate
Not applicable.
Received: 3 May 2016 Accepted: 8 July 2016
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