Serum leptin concentrations during the menstrual cycle in Iranian healthy women.

Abstract

Leptin, a circulating 16-kd polypeptide consisting of 167 amino acids, appears to be involved in the body weight homeostasis. Moreover leptin plays an important role for the reproductive system, early embryogenesis, and fat metabolism during pregnancy and puberty. Significant correlations have been found between leptin and sexual hormones, which is a cytokine and has hormonal properties. The aim of this study was to determine serum leptin levels during the menstrual cycle, and the association between serum leptin and reproductive hormones in young, healthy Iranian women. 42 healthy women volunteered for the study. They all had regular menstrual cycles, with cycle length varying between 26 and 32 days. None of them used oral contraceptives. All were of normal weight, with body mass index ( BMI) < 25 Kg/m2. Fasting blood samples were collected during the follicular phase, mid cycle and luteal phase of the menstrual cycle. FSH and LH were measured with coated tube immunoradiometric assay. Estrogen and progesterone were measured using antibody -coated tubes. Serum Leptin concentration were measured by Leptin (sandwich) ELISA. In menstruating women, serum leptin increased from 13.15+/-1.60 ng/ml in the early follicular phase to 16.57+/-1.68 ng/ml (P<0.01) at the luteal phase. Serum leptin concentration negatively correlated with LH and progesterone (P<0.05). Mean serum leptin levels correlated with body mass index (BMI) (r =0.78, P<0.001).

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ORIGINAL REPORT

*Corresponding Author: Nahid Einollahi
Department of Medical Laboratory Sciences, School of Allied Health Medicine, Tehran University of Medical Sciences, Tehran, Iran
Tel: + 98 21 64053277, Fax:+98 21 88953077, E-mail: naeinollahi@yahoo.co.uk

Serum Leptin Concentrations during the Menstrual Cycle
in Iranian Healthy Women
Nahid Einollahi*, Nasrin Dashti, and Fariba Nabatchian
Department of Medical Laboratory Sciences, School of Allied Health Medicine, Tehran University of Medical Sciences, Tehran, Iran

Received: 30 May 2009; Received in revised form: 25 Aug. 2009; Accepted: 8 Nov. 2009

Abstract- Leptin, a circulating 16-kd polypeptide consisting of 167 amino acids, appears to be involved in
the body weight homeostasis. Moreover leptin plays an important role for the reproductive system, early
embryogenesis, and fat metabolism during pregnancy and puberty. Significant correlations have been found
between leptin and sexual hormones, which is a cytokine and has hormonal properties. The aim of this study
was to determine serum leptin levels during the menstrual cycle, and the association between serum leptin
and reproductive hormones in young, healthy Iranian women. 42 healthy women volunteered for the study.
They all had regular menstrual cycles, with cycle length varying between 26 and 32 days. None of them used
oral contraceptives. All were of normal weight, with body mass index ( BMI) < 25 Kg/m2. Fasting blood
samples were collected during the follicular phase, mid cycle and luteal phase of the menstrual cycle. FSH
and LH were measured with coated tube immunoradiometric assay. Estrogen and progesterone were
measured using antibody –coated tubes. Serum Leptin concentration were measured by Leptin (sandwich)
ELISA. In menstruating women, serum leptin increased from 13.15+/-1.60 ng/ml in the early follicular phase
to 16.57+/-1.68 ng/ml (P<0.01) at the luteal phase. Serum leptin concentration negatively correlated with LH
and progesterone (P<0.05). Mean serum leptin levels correlated with body mass index (BMI) (r =0.78,
P<0.001).
© 2010 Tehran University of Medical Sciences. All rights reserved.
Acta Medica Iranica 2010; 48(5): 300-303.

Key words: Leptin, Menstrual cycle, Iranian women

Introduction

Leptin is a circulating 16 KD polypeptide consisting of
167 amino acids, encoded by obese gene and is located
on chromosome 7 in humans (1). It is a hormone
produced by adipocytes which provides information on
the availability of fat stores to the hypothalamus and acts
as a signal regulating appetite and energy expenditure to
both rodents and humans (2). Leptin concentration is
related to the mass of adipose tissue ,is an adipocyte
secreted hormone and appears to be involved in the
regulation of body weight homeostasis (3). Moreover,
leptin plays an important role for the reproductive
system, in the gonadal function (4,5). It has also been
shown that leptin is involved in early embryogenesis (6),
fat metabolism during pregnancy (7), and puberty (8).
Several authors found circulating leptin in a pulsatile
(3) but also in a circadian and circa cyclic pattern (9,10).
The exact mechanism by which leptin controls
fertility is unknown. There are data controversies
regarding variations of leptin during menstrual cycle and
its relation to the sex hormones (11). Moreover no study
dealing with leptin levels and sex hormones in Iranian
women has been performed. The aim of this study was
to determine serum leptin levels and sex hormones
during menstrual cycle in healthy Iranian women.

Patients and Methods

This study was performed on 42 Iranian women. They
were recruited through advertisements at the Tehran
University Campus and most of them were students.
Written consent was provided by all. Their ages were
between 18-35 years and reported regular menstrual
cycles. Other inclusion criteria were normal BMI (18-25
Kg/m2) and good health without any problem and
endocrine disorders. They all had regular menstrual
cycles, with cycle length varying between 26 and 32
days. None of them used oral contraceptives. All were of
normal weight, with body mass index (BMI) < 25

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N. Einollahi, et al.
Acta Medica Iranica, Vol. 48, No. 5 (2010) 301
Kg/m2. Three separate blood samples were taken 1)
during days 3-5 from onset of menstrual cycle 2)during
days 13-17 (according to basal body temperature of
volunteers) 3)3-5 days before onset of next menstrual
cycle.
All blood samples were drawn after an overnight fast
between 8.00 and10.00A.M from the cubital vein. All
blood samples were allowed to clot and centrifuged
within 30 min after vein puncture. The obtained serum
was divided into two aliquots and frozen at -80◦C until
the measurements were performed.

Measurements of leptin, FSH, LH, estradiol and
progesterone
Serum leptin levels
commercially available highly
kit(Diagnostics Biochem Canada Inc) having the
following intra- and inter-assay variation (AV): <0.05
and 0.<09 .
Commercially available immunoassay kits were used
for FSH (FSH IRMA Kavoshyar, Iran), LH(LH IRMA
Kavoshyar, Iran). Estradiol and progesterone levels were
determined using ELISA kits DRG, Germany).
Statistical Analysis was performed with the SPSS
software version 11.0. The changes of the studied
hormones and leptin throughout the menstrual cycle
were examined with pearson correlation test. All tests
were two-tailed and statistical significance was
considered for P <0.05. Levels of hormones and leptin
were expressed as mean+/-SEM.



were determined
sensitive
by
ELISA
Results

All 42 volunteers had ovulatory cycle as judged by
luteal progesterone levels above 5 ng/ml. General
characteristics of the women included in this study are
shown in table 1. In menstruating women the mean
serum concentrations of
progesterone and leptin of subjects during three phases
of a full menstrual cycle are shown in table 2. The serum
leptin levels showed a large variation during
menstruation cycle in healthy women. Regarding the
three phases of menstrual cycle ,the mean leptin
concentrations during the follicular phase (13.15 +/-
1.6ng/ml) were significantly lower compared to the
luteal phase (16.57+/-1.68 ng/ml, P=0.015). No
significant difference was observed between the
midcycle and the luteal phase (P=0.17). Also no
significant difference was observed between the leptin
levels in follicular and midcycle phase (P=0.16). The
serum leptin concentrations were analyzed in relation to
the sex hormones. Significant correlations were found
in the follicular phase between leptin and LH levels
(r=-0.314). Also there is a significant correlation
between leptin and progesterone concentrations
(r=-0.360). No correlation between leptin levels and
FSH (r = 0.03), or leptin and estradiol (r = -0.18) was
found, during different phases of menstrual cycle. Also
there was a strong positive correlation between leptin
concentrations and BMI independent of the cycle stage
(r=0.78, p<0.001) (Figure 1).
FSH, LH, estradiol,
Table 1. Basic charachteristics of subjects studied
Parameter
Age
Weight
Height
BMI
No.
42
42
42
42
Mean±SEM
27.28±1.24
58.37±1.35
1.62±0.08
22.23±0.47



Table 2. Concentrations of Leptin,FSH,LH,estradiol and progesterone of 42 healthy women
during three phases of a full menstrual cycle. Mean values ± SEM are presented.
Parameter
Leptin(ng/ml
FSH(µIU/ml
LH(µIU/ml)
Estradiol(pg/ml)
Progestrone(ng/ml)
Follicular phase
13.15±1.6
5.12±0.37
3.47±0.25
26.81±1.60
0.79±0.19
Midcycle
16.04±2.05
5.09±0.41
13.33±2.24
104±11.5
2.16±0.48
Luteal phase
16.57±1.68
3.21±0.32
3.67±0.46
84.0±6.63
7.16±0.76

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Serum leptin concentrations during the menstrual cycle
302 Acta Medica Iranica, Vol. 48, No. 5 (2010)

18.0020.0022.0024.00
BMI ( kg/m2)
0.00
20.00
40.00
60.00
80.00
Leptin( ngr/ml)

Figure 1. Leptin concentrations in healthy women(n=42)in
correlation to body mass index (BMI).Leptin l in serum
correlate with BMI:r=.78,p<.001.evels


Discussion

In this study we demonstrated that blood samples from
healthy Iranian women show significantly higher serum
leptin concentration during the luteal, compared to the
follicular phases. We also found correlation between
leptin and LH and progestrone levels, but any
correlation between leptin levels and FSH or leptin
levels and estradiol, was not found.
These results are in accordance with a number of
other studies which have shown considerable variation
in leptin levels throughout the menstrual cycles with
higher levels in the luteal rather than the follicular phase
(12-20). A few studies demonstrate that leptin is a
mediator of cell proliferation and with respect to the
presence of leptin receptors in the endometrium,its
plausible that the leuteal phase of the menstrual cycle is
accompanied by increased leptin levels. Also the
preovulatory surge of estrogen might increase the
circulating leptin ,which in turn could stimulate the
gonads to produce more leptin together with increasing
levels of progesterone (21-23).
However other studies also have shown either small
but insiginificant trends at the end of cycle (24), or no
fluctuation at all (25,26). Regarding to the correlations
between sexual hormones and leptin ,although several
studies have shown a correlation between leptin levels
with changes in serum estradiol, progesterone and/or LH
but results are not uniform and is unclear (15,17-
19,24,26,27).
Finally regarding to the correlation of serum leptin
level with body mass index we found a strong
correlation between serum leptin concentration and
BMI, where it is similar to the other researchers have
reported in several studies (2,27,28).
Our study has several limitations .Our sample size is
small,and there was a large amount of variability in both
leptin levels and sex hormones. Although ,this suggests
a greater deal of variability within the normal
population. However in summary ,our findings are in
accordance to several other researchers in this area and
this is the first report of leptin fluctuations during
menstrual cycle in Iranian healthy women.
Thus it is hoped that the ongoing research efforts
will not only fully elucidate the relation between leptin
and sex hormones, but will also result in better
understanding of the role of leptin in Iranian women
health.

Acknowledgements

This study was supported by a grant from research vice
chancellor of Tehran University of Medical Sciences.

References

1. Zhang Y, Proenca R, Maffei M, Barone M, Leopold L,
Friedman JM. Positional cloning of the mouse obese gene
and its human homologue. Nature 1994;372(6505):425-32.
2. Schubring C, Prohaska F, Prohaska A, Englaro P, Blum W,
Siebler T, et al. Leptin concentrations in maternal serum
and amniotic fluid during the second trimenon: differential
relation to fetal gender and maternal morphometry. Eur J
Obstet Gynecol Reprod Biol 1999;86(2):151-7.
3. Geisthövel F, Jochmann N, Widjaja A, Horn R, Brabant G.
Serum pattern of circulating free leptin, bound leptin, and
soluble leptin receptor in the physiological menstrual
cycle. Fertil Steril 2004;81(2):398-402.
4. Karlsson C, Lindell K, Svensson E, Bergh C, Lind P,
Billig H, et al. Expression of functional leptin receptors in
the human ovary. J
1997;82(12):4144-8.
5. Okudan N, Gökbel H, Uçok K, Baltaci A. Serum leptin
concentration and anaerobic performance do not change
during the menstrual cycle of young females. Neuro
Endocrinol Lett 2005;26(4):297-300.
6. Antczak M, Van Blerkom J. Oocyte influences on early
development: the regulatory proteins leptin and STAT3 are
polarized in mouse and human oocytes and differentially
distributed within the cells of the preimplantation stage
embryo. Mol Hum Reprod 1997;3(12):1067-86.
Clin Endocrinol Metab

Page 4

N. Einollahi, et al.
Acta Medica Iranica, Vol. 48, No. 5 (2010) 303
7. Butte NF, Hopkinson JM, Nicolson MA. Leptin in human
reproduction: serum leptin levels in pregnant and lactating
women. J Clin Endocrinol Metab 1997;82(2):585-9.
8. Chehab FF, Mounzih K, Lu R, Lim ME. Early onset of
reproductive function in normal female mice treated with
leptin. Science 1997;275(5296):88-90.
9. Licinio J, Negrão AB, Mantzoros C, Kaklamani V, Wong
ML, Bongiorno PB, et al. Synchronicity of frequently
sampled, 24-h concentrations of circulating leptin,
luteinizing hormone, and estradiol in healthy women. Proc
Natl Acad Sci U S A 1998;95(5):2541-6.
10. Sinha MK, Ohannesian JP, Heiman ML, Kriauciunas A,
Stephens TW, Magosin S, et al. Nocturnal rise of leptin in
lean, obese, and non-insulin-dependent diabetes mellitus
subjects. J Clin Invest 1996;97(5):1344-7.
11. Moschos S, Chan JL, Mantzoros CS. Leptin and
reproduction: a review. Fertil Steril 2002;77(3):433-44.
12. Hardie L, Trayhurn P, Abramovich D, Fowler P.
Circulating leptin in women: a longitudinal study in the
menstrual cycle and during pregnancy. Clin Endocrinol
(Oxf) 1997;47(1):101-6.
13. Messinis IE, Milingos S, Zikopoulos K, Kollios G,
Seferiadis K, Lolis D. Leptin concentrations in the
follicular phase of spontaneous cycles and cycles
superovulated with follicle stimulating hormone. Hum
Reprod 1998;13(5):1152-6.
14. Riad-Gabriel MG, Jinagouda SD, Sharma A, Boyadjian R,
Saad MF. Changes in plasma leptin during the menstrual
cycle. Eur J Endocrinol 1998;139(5):528-31.
15. Quinton ND, Laird SM, Okon MA, Li TC, Smith RF, Ross
RJ, et al. Serum leptin levels during the menstrual cycle of
healthy fertile women. Br J Biomed Sci 1999;56(1):16-9.
16. Paolisso G, Rizzo MR, Mazziotti G, Rotondi M,
Tagliamonte MR, Varricchio G, et al. Lack of association
between changes in plasma leptin concentration and in
food intake during the menstrual cycle. Eur J Clin Invest
1999;29(6):490-5.
17. Cella F, Giordano G, Cordera R. Serum leptin
concentrations during the menstrual cycle in normal-
weight women: effects of an oral triphasic estrogen-
progestin medication. Eur J Endocrinol 2000;142(2):174-8.
18. Fernández-Real JM, Gutierrez C, Vendrell J, Casamitjana
R, Ricart W. Plasma soluble tumor necrosis factor-alpha
receptors circulate in proportion to leptin levels during the
menstrual cycle in lean but not in obese women. Eur J

Endocrinol 2000;143(2):235-41.
19. Ludwig M, Klein HH, Diedrich K, Ortmann O. Serum
leptin concentrations throughout the menstrual cycle. Arch
Gynecol Obstet 2000;263(3):99-101.
20. Asimakopoulos B, Milousis A, Gioka T, Kabouromiti G,
Gianisslis G, Troussa A, et al. Serum pattern of circulating
adipokines throughout the physiological menstrual cycle.
Endocr J 2009;56(3):425-33.
21. Tsuchiya T, Shimizu H, Horie T, Mori M. Expression of
leptin receptor in lung: leptin as a growth factor. Eur J
Pharmacol 1999;365(2-3):273-9.
22. Wolf G, Hamann A, Han DC, Helmchen U, Thaiss F,
Ziyadeh FN, et al. Leptin stimulates proliferation and
TGF-beta expression in renal glomerular endothelial cells:
potential role in glomerulosclerosis [seecomments].
Kidney Int 1999;56(3):860-72.
23. Sirotkin AV, Grossmann R. Leptin directly controls
proliferation, apoptosis and secretory activity of cultured
chicken ovarian cells. Comp Biochem Physiol A Mol
Integr Physiol 2007;148(2):422-9.
24. Teirmaa T, Luukkaa V, Rouru J, Koulu M, Huupponen R.
Correlation between circulating leptin and luteinizing
hormone during the menstrual cycle in normal-weight
women. Eur J Endocrinol 1998;139(2):190-4.
25. Stock SM, Sande EM, Bremme KA. Leptin levels vary
significantly during the menstrual cycle, pregnancy, and in
vitro fertilization treatment: possible relation to estradiol.
Fertil Steril 1999;72(4):657-62.
26. Lin KC. Changes of circulating leptin levels during normal
menstrual cycle: relationship to estradiol and progesterone.
Kaohsiung J Med Sci 1999;15(10):597-602.
27. Al-Harithy RN, Al-Doghaither
Correlation of leptin and sex hormones with endocrine
changes in healthy Saudi women of different body
weights. Ann Saudi Med 2006;26(2):110-5.
28. Maruyama S, Minami S, Kaseki H, Ishihara K, Araki S,
Suzue R. A comparison of serum leptin concentrations in
obese and normal weight Japanese women with regular
menstrual cycle. J Nutr Sci Vitaminol (Tokyo)
2001;47(1):87-9.
29. 29. Fenichel RM, Dominguez JE, Mayer L, Walsh BT,
Boozer C, Warren MP. Leptin levels and luteinizing
hormone pulsatility in normal cycling women and their
relationship to daily changes in metabolic rate. Fertil Steril
2008;90(4):1161-8.
H, Abualnaja K.