Lower levels of TSH are associated with a lower risk of papillary thyroid cancer in patients with thyroid nodular disease: Thyroid autonomy may play a protective role

Abstract

Higher TSH values, even within normal ranges, have been associated with a greater risk of thyroid malignancy. The relationship between TSH and papillary thyroid cancer (PTC) has been analyzed in 10 178 patients submitted to fine needle aspiration of thyroid nodules with a cytology of PTC (n=497) or benign thyroid nodular disease (BTND, n=9681). In 942 patients, submitted to surgery (521 from BTND and 421 from PTC), the histological diagnosis confirmed an elevated specificity (99.6%) and sensitivity (98.1%) of cytology. TSH levels were significantly higher in PTC than in BTND both in the cytological and histological series and also in patients with a clinical diagnosis of multinodular goiter (MNG) and single/isolate nodule (S/I). A significant age-dependent development of thyroid autonomy (TSH <0.4 microU/ml) was observed in patients with benign thyroid disease, but not in those with PTC, diagnosed both on cytology and histology. In patients with MNG, the frequency of thyroid autonomy was higher and the risk of PTC was lower compared to those with S/I. In all patients, the presence of thyroid auto-antibodies (TAb) was associated with a significant increase of TSH. However, both in TAb positive and TAb negative patients TSH levels were significantly higher in PTC than in BTND. Our data confirm a direct relationship between TSH levels and risk of PTC in patients with nodular thyroid diseases. Thyroid autonomy conceivably protects against the risk of PTC, while thyroid autoimmunity does not play a significant role.

Full text

Lower levels of TSH are associated with a
lower risk of papillary thyroid cancer in
patients with thyroid nodular disease:
thyroid autonomy may play a protective role
E Fiore, T Rago, M A Provenzale, M Scutari, C Ugolini
1
, F Basolo
1
, G Di Coscio
2
,
P Berti
3
, L Grasso, R Elisei, A Pinchera and P Vitti
Department of Endocrinology,
1
Section of Pathology,
2
Section of Cytopathology and
3
Department of Surgery, University of Pisa,
via Paradisa 2, 56100 Pisa, Italy
(Correspondence should be addressed to E Fiore; Email: e.fiore@ao-pisa.toscana.it)
Abstract
Higher TSH values, even within normal ranges, have been associated with a greater risk of thyroid
malignancy. The relationship between TSH and papillary thyroid cancer (PTC) has been analyzed
in 10 178 patients submitted to fine needle aspiration of thyroid nodules with a cytology of PTC
(nZ497) or benign thyroid nodular disease (BTND, nZ9681). In 942 patients, submitted to
surgery (521 from BTND and 421 from PTC), the histological diagnosis confirmed an elevated
specificity (99.6%) and sensitivity (98.1%) of cytology. TSH levels were significantly higher in PTC
than in BTND both in the cytological and histological series and also in patients with a clinical
diagnosis of multinodular goiter (MNG) and single/isolate nodule (S/I). A significant age-
dependent development of thyroid autonomy (TSH !0.4 mU/ml) was observed in patients with
benign thyroid disease, but not in those with PTC, diagnosed both on cytology and histology.
In patients with MNG, the frequency of thyroid autonomy was higher and the risk of PTC was lower
compared to those with S/I. In all patients, the presence of thyroid auto-antibodies (TAb) was
associated with a significant increase of TSH. However, both in TAb positive and TAb negative
patients TSH levels were significantly higher in PTC than in BTND. Our data confirm a direct
relationship between TSH levels and risk of PTC in patients with nodular thyroid diseases. Thyroid
autonomy conceivably protects against the risk of PTC, while thyroid autoimmunity does not play a
significant role.
Endocrine-Related Cancer (2009) 16 1251–1260
Introduction
Thyroid cancer is the most common malignant tumor
of the endocrine system. In 2003, the American Cancer
Society reported an incidence in the USA of
1/10 000, increasing with a rate higher than 5% per
year for a decade (Davies & Welch 2006). Papillary
thyroid cancer (PTC) accounts for more than 80% of
all thyroid malignancies (Hundahl et al. 1998).
TSH is involved in the regulation of thyroid function
such as secretion of thyroid hormones, maintenance of
thyroid-specific gene expression (differentiation), and
gland growth. Experimental studies and clinical data
have demonstrated that thyroid-cell proliferation is
dependent on TSH and that well-differentiated thyroid
cancers usually retain responsiveness to TSH. These
observations provide the rationale for TSH suppression
as a treatment for differentiated thyroid cancer (Biondi
et al. 2005). Several reports have shown that
patients with well-differentiated thyroid cancers
respond to TSH suppressive treatment with L-thyroxine
(L-T
4
), resulting in decreased disease progression,
recurrence rates, and cancer-related mortality
(Mazzaferri & Jhiang 1994,Mazzaferri 1999,Sipos
& Mazzaferri 2008).
Endocrine-Related Cancer (2009) 16 1251–1260
Endocrine-Related Cancer (2009) 16 1251–1260
1351–0088/09/016–001251 q2009 Society for Endocrinology Printed in Great Britain
DOI: 10.1677/ERC-09-0036
Online version via http://www.endocrinology-journals.org

Recently it has been reported that in patients with
nodular thyroid diseases, the risk of malignancy
increases with serum TSH concentrations and, even
within normal ranges, higher TSH values are associ-
ated with a significantly greater likelihood of thyroid
cancer (Boelaert et al. 2006,Jonklaas et al. 2008,
Polyzos et al. 2008). Higher TSH levels have also been
associated with advanced stage thyroid cancer and it
has been suggested that TSH may play a central role in
its development and progression (Haymart et al.
2008b). However, in some of these studies (Boelaert
et al. 2006,Polyzos et al. 2008) different thyroid
malignancies were grouped, including medullary or
anaplastic cancers or thyroid lymphomas, that have
never been reported to be TSH dependent. Besides, in
other studies (Haymart et al. 2008b,Jonklaas et al.
2008) only patients submitted to thyroid surgery were
included, and it is not possible to rule out a potential
selection bias because histological series usually do not
include patients with small benign nodular goiter.
In this work, we intended to study the relationship
between TSH and PTC in a large and homogeneous
series of patients subjected to fine needle aspiration
(FNA), after validating the results of cytology in a
subgroup of patients submitted to surgery. We also
intended to analyze the relationship between PTC,
TSH and the presence of serum thyroid auto-
antibodies (TAb). To this purpose, we ruled out
possible factors that may affect TSH levels,
including in the study only patients who were not
on therapy with L-T
4
or methimazole. Our results
indicate that the detection of higher TSH levels in
PTC than in benign thyroid nodular disease (BTND)
is mainly related to the development of thyroid
‘autonomy’ in nodular goiter, rather than thyroid
autoimmunity in PTC.
Patients and methods
Patients
During the years 1997–2004, 33 774 patients under-
went FNA biopsy of thyroid nodules cold at scintiscan
in our department. Among these, we selected 10 178
patients (males, 2007; females, 8171; mean age
49.2G13.2 years), who were included in the present
study because they fulfilled the following criteria:
a) they had a diagnostic cytological exam (patients
with non-diagnostic or indeterminate cytology
were excluded)
b) they were not taking L-T
4
or methimazole and were
not overtly hyperthyroid or hypothyroid
c) they had TSH, free thyroid hormones, and
anti-thyroid antibodies measured simultaneously
with FNA
d) the diagnosis of Graves’ disease and Hashimoto’s
thyroiditis had been excluded on clinical grounds.
Patients were defined as affected by nodular
Hashimotos’ thyroiditis if they showed a diffused
hypoecoic ‘thyroiditis’ pattern at thyroid ultra-
sound and had high levels of anti-thyroglobulin
(TgAb) and/or anti-thyroperoxidase (TPOAb)
antibodies. The diagnosis of Graves’ disease
was made according to usual standard criteria
including active or treated hyperthyroidism,
goiter with diffused hypoecoic pattern at thyroid
ultrasound, ophthalmopathy, and serum positive
for anti-TSH receptor antibodies, and/or TgAb or
TPOAb.
All patients gave their informed consent to the study.
According to clinical findings, ultrasound examination
and thyroid scintiscan patients were subdivided into
two diagnostic groups. The patients with single/isolate
(S/I) thyroid nodule (nZ3577) had a single, cold
nodule in a normal or slightly enlarged thyroid gland.
The multinodular goiter (MNG) patients (nZ6601)
presented a goiter with multiple nodules at ultrasound
examination. At thyroid scan they had only cold
nodules or both cold and ‘hot’ nodules. In these
patients, FNA biopsy was performed only on cold
thyroid nodules.
Thyroid function tests
Serum free T
4
(FT
4
) and triiodothyronine (FT
3
) were
measured by RIA (FT
4
by Liso-Phase kit – normal
values 7–17 pg/ml; FT
3
by Liso-Phase kit – normal
values K2.7–5.7 pg/ml; Technogenetics, s.r.l., Milan,
Italy). Serum TSH was measured by a sensitive
immunoradiometric assay (Delphia Pharmacia,
Turku, Finland – normal values 0.4–3.4 mU/ml).
TgAb and TPOAb were measured by an immunoenzy-
matic assay (AIA-Pack TgAb, and TPOAb, Tosoh,
Tokyo, Japan) and expressed as U/ml. Normal values
were !30 U/ml for TgAb and !10 U/ml for TPOAb.
FNA, cytological and histological diagnosis
FNA was performed under echo guidance using a
23-gauge needle attached to a 10 ml syringe. The
material was air-dried, stained with Papanicolaou and
Giemsa and interpreted by an experienced cytologist
(G D C). The adequacy of aspirates was defined
according to the guidelines of the Papanicolaou
E Fiore et al.: TSH and risk of PTC
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Society (The Papanicolaou Society of Cytopathology
Task Force on Standards of Practice 1996) and
cytological results were classified according to the
criteria of British Thyroid Association (2007).
For histological diagnosis, formalin-fixed, paraffin-
embedded nodular tissues were stained by hematoxylin
and eosin. The diagnosis was made blindly by two
independent pathologists (F B, C U), according to the
World Health Organization guidelines. When the
results were discordant, agreement was found by
conjoint re-examination of each case. In patients with
PTC, cancer was staged according to the TNM
classification (Sobin 2002).
Statistical analysis
TSH values were expressed as median and interquartile
range (25–75p). Non-parametric tests (c
2
, Mann–
Whitney or Kruskall–Wallis) were used as appropriate
and considered statistically significant where P!0.05.
Results
FNA cytology and histological validation
On the whole, 497/10 178 (4.9%) patients had a FNA
cytology suggestive or indicative of PTC (PTC group),
and 9681/10 178 (95.1%) had one or more cytological
benign thyroid nodules and were included in the BTND
group. The soundness of cytological diagnosis was
evaluated in a sample of 942 patients submitted to
surgery. This group included the majority (421/497,
85%) of patients with a cytological diagnosis of PTC
and 521 patients of BTND group who had been
submitted to surgery. The histological diagnosis of
PTC was confirmed in 419/421 (99.5%) patients with
a cytology suggestive or indicative of PTC and was
found in 9/521 (1.7%) patients with cytological diag-
nosis of BTND. Thus, FNA cytology had an elevated
specificity (99.6%) and sensitivity (98.1%). In our
series, the positive predictive value of cytology was
99.5% and the negative predictive value was 98.3%.
Free thyroid hormones and TSH values in BTND
and PTC patients
As shown in Table 1, in the large group of patients
submitted to FNA, serum TSH levels in PTC patients
(median 1.10 mU/ml; 25–75p 0.70–1.70 mU/ml) were
significantly higher than in BTND (median
0.70 mU/ml; 25–75p 0.30–1.20 mU/ml). In contrast
to what was observed with TSH values, serum
FT
3
and FT
4
levels were not significantly different
in BTND and PTC. However, serum FT
3
was
significantly higher in patients with thyroid autonomy
(i.e. TSH !0.4 mU/ml) with respect to those with
normal TSH values, both in PTC and BTND
(Table 2).
Also in the subgroup of patients submitted to
surgery, serum TSH levels were significantly higher
(P!0.001) in PTC (median 1.10 mU/ml; 25–75p
0.70–1.80 mU/ml) than in BTND (median
0.50 mU/ml; 25–75p 0.17–0.90 mU/ml), confirming
the results observed in the whole cytological series
(data not shown).
Prevalence of PTC according to serum TSH levels
In the whole group of patients, 2024/10 178 (19.8%)
had subclinical or overt hyperthyroidism, i.e. serum
TSH concentrations below the normal range
(0.4 mU/ml), and normal or elevated serum-free
thyroid hormones respectively. A total of 7893 patients
had serum TSH levels within the normal range. These
subjects were subdivided into four quartiles of similar
size according to their TSH values. A group of 261
patients with nodular thyroid disease had serum TSH
levels slightly higher than normal, ranging from 3.5 to
10 mU/ml. Anti-thyroid antibodies were detected in
183/261 (70.1%) of these patients who conceivably
had an autoimmune thyroiditis, even in the absence of
Table 1 Free thyroid hormones and TSH levels (expressed as
median and interquartile range) in benign thyroid nodular
disease (BTND) and papillary thyroid cancer (PTC) groups
BTND PTC Pvalue
a
FT
3
(pg/ml)
3.6 (3.1–4.0) 3.6 (3.1–3.9) NS
FT
4
(pg/ml)
10.9 (9.6–12.4) 10.9 (9.7–12.5) NS
TSH
(mU/ml)
0.70 (0.30–1.20) 1.10 (0.70–1.70) !0.0001
a
Mann–Whitney test.
Table 2 Free triiodothyronine (FT
3
; pg/ml) levels (expressed
as median and interquartile range) in benign thyroid nodular
disease (BTND) and papillary thyroid cancer (PTC) groups in
patients with TSH !or R0.4 mU/ml. The number of patients
(n) in each group is indicated
TSH
!0.4 mU/ml
(nZ2024)
TSH
R0.4 mU/ml
(nZ8154) Pvalue
a
BTND (nZ9681) 3.9 (3.4–4.6)
(nZ1979)
3.5 (3.1–3.9)
(nZ7702)
!0.0001
PTC (nZ497) 3.9 (3.5–4.8)
(nZ45)
3.6 (3.1–3.4)
(nZ452)
!0.0001
a
Mann–Whitney test.
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the characteristic hypoecoic pattern at ultrasound
examination. The prevalence of PTC according to
serum TSH concentrations is shown in Fig. 1. The
frequency of PTC was higher in subjects with higher
TSH values, being the lowest in patients with
subnormal TSH values (51/2024; 2.5%) and the
highest in patients with TSH values between 1.6 and
3.4 mU/ml (152/1665; 9.1%). It is worth underlining
that in patients with TSH between 3.5 and 10 mU/ml
the frequency of PTC (21/261; 8.0%) was not
significantly different with respect to patients with
TSH in the upper limit of normal range (c
2
test
PZ0.1). The odd ratio and 95% confidence interval of
PTC according to TSH levels are reported in Table 3.
TSH value in BTND and PTC patients according
to age
As shown in Fig. 2, panel A, serum TSH levels showed
a significant reduction with age (Kruskall–Wallis,
P!0.0001), as expected in patients with nodular
thyroid disease. When TSH levels according to age
were analyzed separately in PTC and BTND (Fig. 2,
panel B), TSH was significantly higher in PTC than
BTND in all age groups. Interestingly, BTND patients
showed a significant, age-dependent reduction of TSH
values (Kruskall–Wallis, P!0.0001), while in PTC the
reduction of TSH in older patients was less evident and
only slightly significant (Kruskall–Wallis, PZ0.03).
Thyroid functional autonomy, defined as serum TSH
levels below the lower limit of the normal range
(0.4 mU/ml), was found in 1973/9681 (20.4%) BTND
and 51/497 (10.3%) PTC (c
2
,P!0.0001). While in
PTC the frequency of thyroid autonomy showed no
age-dependent distribution, in BTND it was
progressively increasing with age and was significantly
higher than PTC in all classes of age with the exception
of younger subjects (Fig. 3, panel A). In patients
submitted to surgery, the age-dependent thyroid
autonomy presented a similar pattern, showing a
significant increase in older patients only in the
BTND group (Fig. 3, panel B). This finding confirmed
the results observed in the whole cytological series.
Risk of PTC according to clinical diagnosis
and thyroid autonomy
The overall risk of PTC was significantly lower in
MNG than in S/I both in the whole group (234/6601,
3.5% vs 263/3577, 7.3%; c
2
,P!0.0001) and in the
subgroups of patients classified according to the
presence of thyroid autonomy (22/1595, 1.4% vs
23/429, 5.4%; c
2
,P!0.0001) or its absence
(212/5006, 4.2% vs 240/3148, 7.6%; c
2
,P!0.0001)
(Fig. 4, panel A). In patients with MNG the risk of PTC
was much higher in those with TSH R0.4 mU/ml
(212/5006, 4.2%) than in those with thyroid autonomy
(22/1595, 1.4%; c
2
,P!0.0001.), while in patients
with S/I this difference did not reach statistical
significance (240/3148, 7.6% vs 23/429, 5.4%;
c
2
,PZ0.09) (Fig. 4, panel A).
As expected, thyroid autonomy was much more
frequent in patients with MNG (1595/6601, 24.1%)
than those with S/I (429/3577, 11.9%; c
2
,P!0.0001,
not shown). In patients with MNG thyroid autonomy
was much more frequent in patients with the
cytological diagnosis of BTND (1573/6367, 24.7%)
than in those with PTC (22/234, 9.4%; c
2
,P!0.0001),
while in S/I the prevalence of thyroid autonomy was
not significantly different between patients with benign
(406/3314, 12.2%) and malignant cytology (23/263,
8.7%; c
2
,PZ0.09) (Fig. 4, panel B).
TSH values and PTC stage
Patients with PTC were grouped according to TNM
and results are shown in Fig. 5. TSH values in
patients with stage T3–T4 (nZ170/497, 34.2% median
Figure 1 Prevalence of PTC according to serum TSH
concentrations. Patients with serum TSH level within the
normal range were divided into four quartiles of similar size
according to their TSH values. Patients with serum TSH levels
lower (0.4 mU/ml) or higher (from 3.5 to 10 mU/ml) than the
normal range values were considered separately. The odd ratio
and 95% confidence interval of PTC according to TSH levels
are reported in Table 3.
Table 3 Odd ratio (OR) and 95% confidence interval (CI) of
papillary thyroid cancer (PTC) according to TSH levels
TSH (mU/ml) OR 95% CI Pvalue
a
0.40–0.59 0.80 0.51–1.27 0.18
0.60–0.89 2.01 1.46–2.77 !0.0001
0.90–1.59 2.66 1.98–3.58 !0.0001
1.60–3.40 4.29 3.17–5.08 !0.0001
O3.40 3.50 2.10–5.83 0.0011
a
Binary logistic regression analysis.
E Fiore et al.: TSH and risk of PTC
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TSH 1.30 mU/ml; 25–75p 0.85–1.95 mU/ml) were
significantly higher (Mann–Whitney, PZ0.001) than
in patients with stage T1–T2 (nZ327/497, 65.8%
median TSH 1.00 mU/ml; 25–75p 0.60–1.60 mU/ml).
When patients were divided according to the presence
or the absence of neck node metastasis, TSH values in
patients with N1 (nZ159/497, 32.0%, median TSH
1.40 mU/ml; 25–75p 0.90–1.90 mU/ml) were signi-
ficantly higher (Mann–Whitney, PZ0.002) than in
patients with N0 (nZ338/497, 68.0%, median TSH
1.00 mU/ml; 25–75p 0.60–1.70 mU/ml). Distant metas-
tasis were detected only in 5/497 (1%) patients and
because of this low number TSH values in M1 versus
M0 patients were not analyzed.
TSH value in BTND and PTC patients according
to the presence of TAb
To address the question of the possible effect of
thyroid autoimmunity on TSH levels, we also analy-
zed TSH levels according to the presence of TAbs.
In TAb positive patients TSH (0.70 mU/ml; 25–75p
0.30–1.20 mU/ml) was significantly higher (Mann–
Whitney, PZ0.002) than in TAb negative subjects
(0.70 mU/ml; 25–75p 0.30–1.30 mU/ml). It is worth
pointing out that, even if median TSH levels were
identical in both in TAb positive and negative
patients, the TSH values in the upper quartile were
higher in TAb positive than TAb negative subjects,
accounting for the significant statistical difference
observed between these two groups.
Serum TSH levels were significantly higher in PTC
than in BTND both in TAb positive and negative
patients (Fig. 6). In TAb positive patients the median
Figure 2 Box-whisker plots illustrating median, quartiles, and
ranges of TSH levels according to age. As shown in panel A,
serum TSH levels show a significant reduction with age
(Kruskall–Wallis test, P!0.0001). The number of patients
included in each age group is indicated in the bottom of the
figure. When BTND (white box) and PTC (gray box) patients
were grouped according to age (B), TSH was significantly
higher in PTC than in BTND in all age groups (*Zc
2
,
P!0.01). Besides, BTND patients showed a significant, age-
dependent reduction of TSH values (Kruskall–Wallis test,
P!0.0001), while in PTC the reduction of TSH in older
patients was less evident and only slightly significant
(Kruskall–Wallis test, PZ0.03). The number of patients with
BTND and PTC in each age group is indicated in the bottom
of the figure.
Figure 3 Frequency of thyroid autonomy in PTC (gray bars) and
BTND (white bars) according to age in patients with thyroid
autonomy. In BTND patients, a progressive, age-dependent
increase of thyroid autonomy was observed, while no age-
dependent distribution was present in PTC patients. With the
exception of younger subjects, the frequency of thyroid
autonomy was significantly higher in BTND than PTC in all
classes of age (*Zc
2
,P!0.01). Similar results were observed
both in the whole cytological series (panel A) and in the
subgroup of patients submitted to surgery (panel B). The
number of patients with thyroid autonomy (BTNDCPTC) in
each age group is reported in the bottom of the figure. The total
number of patients in each age group is indicated in Fig. 2.
Endocrine-Related Cancer (2009) 16 1251–1260
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level of TSH was 1.20 mU/ml (25–75p 0.70–
1.80 mU/ml) in PTC and 0.70 mU/ml (25–75p 0.30–
1.30 mU/ml) in BTND (Mann–Whitney, P!0.0001).
In TAb negative patients the median level of TSH was
1.10 mU/ml (25–75p 0.70–1.70 mU/ml) in PTC and
0.70 mU/ml (25–75p 0.30–1.11 mU/ml) in BTND
(Mann–Whitney, P!0.0001). The frequency of PTC
was not significantly different (c
2
,PZ0.21 NS)
between TAb negative (300/5593, 5.1%) and TAb
positive (197/4205, 4.6%) patients.
Discussion
Well-differentiated thyroid cancer usually retains
responsiveness to TSH and for this reason TSH
suppression therapy with L-T
4
plays an important role
in its treatment (Mazzaferri & Young 1981,Mazzaferri
1991,1999,Mazzaferri & Jhiang 1994,Biondi et al.
2005,Sipos & Mazzaferri 2008). In this work,
we analyzed the relationship between serum TSH
levels and risk of PTC in a large series of patients
subjected to FNA cytology of thyroid nodules. We
decided to focus only on PTC because is the most
frequent thyroid cancer, accounting for more than 80%
of all thyroid malignancies and, as is follicular
thyroid cancer, is TSH dependent. Furthermore, the
cytological diagnosis of PTC is usually highly
dependable, while the diagnosis of follicular thyroid
cancer requires histological examination in order to
evaluate infiltration of the tumor capsule or vessels.
We validated the reliability of cytological exam in a
subgroup of patients submitted to surgery and in our
series the positive and negative predictive values of
cytology were very high, being 99.5 and 98.3%
respectively.
After confirming the soundness of cytology, we
studied a large series of untreated patients with thyroid
nodules subjected to FNA, only including subjects
with a well-defined cytological diagnosis (patients
with non-diagnostic or indeterminate cytology were
Figure 4 Panel A, frequency of PTC in the whole groups of
patients with MNG and S/I (black bars) and in the same patients
subdivided according to the presence (gray bars) or the
absence (white bars) of thyroid autonomy. Panel B, frequency
of thyroid autonomy according to clinical diagnosis (MNG and
S/I) in patients with BTND (white bars) and those with PTC
(gray bars). The statistical differences between the groups
(c
2
and Pvalues) are reported.
Figure 5 Box-whisker plot illustrating median, quartiles, and
ranges of TSH levels in PTC according to TNM. Panel A: TSH
levels in patients with stage T3–T4 (striped box) were
significantly higher (Mann–Whitney test P!0.001) than in stage
T1–T2 (white box). Panel B: TSH values in patients with N1
(dotted columns) were significantly higher (Mann–Whitney
PZ0.002) than in patients with N0 (gray columns).
E Fiore et al.: TSH and risk of PTC
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excluded). By including a selection of patients, these
inclusion criteria allowed us to evaluate the relation-
ship between TSH levels and thyroid cancer in a large
and homogeneous cytological series, avoiding the
obvious selection bias of histological series that do
not include patients with small nodular goiter. Besides,
we ruled out possible factors that may affect TSH
levels, by including only patients who were not on
therapy with L-T
4
or methimazole and patients who
were not affected by Hashimoto’s thyroiditis and
Graves’ disease, diagnosed on clinical grounds. Even
though these inclusion criteria determined a selection
of patients, this procedure must be carried out in order
to exclude both treatments and thyroid diseases that
may affect TSH levels.
Our results demonstrate that TSH levels are slightly,
but significantly higher in PTC compared to benign
thyroid diseases and that the prevalence of PTC
increases with TSH, being the highest in patients
with serum TSH in the upper limit of the normal range.
In agreement with these observations, we found a
significantly higher TSH level in PTC compared with
BTNDs in a subgroup of patients submitted to surgery,
in whom the cytological diagnosis had been validated
by histology. These findings confirm the results
reported by Boelaert et al. (2006), who found an
increased risk of thyroid malignancy in patients with
higher TSH levels. However, in this study different
thyroid cancers were considered together, including
thyroid lymphomas and medullary thyroid cancers
which are not supposed to be TSH dependent. Besides,
only 20 patients with thyroid malignancy were
diagnosed by cytology and the majority of thyroid
cancers were detected on histology, representing a
possible selection bias. On the other hand, our results
were obtained in a large cytological series and were
confirmed in a wide subgroup of patients submitted to
surgery. An increased risk of differentiated thyroid
cancer in patients with higher TSH has been reported
also by Haymart et al. (2008b). In this work, only a
histological series has been evaluated and the
possibility of bias cannot be ruled out, as the
prevalence of thyroid cancer in this series
(241/843Z28.1%) quite high compared with the
frequency of differentiated thyroid cancer in patients
with nodular thyroid disease.
In the whole group of patients included in the present
study, serum TSH levels decrease progressively with
age. This finding has already been observed in iodine
deficient areas, such as those the majority of our
patients came from, where longstanding iodine
deficiency causes higher frequency of thyroid nodular-
ity and autonomy in older people (Fenzi et al. 1985,
Vitti et al.1990,Aghini-Lombardi et al. 1999). When
patients were classified as affected by benign thyroid
disease or PTC according to the results of cytology, the
age-dependent reduction of TSH levels was highly
significant in the first group, while in patients with PTC
this phenomenon was much less evident. Indeed, the
TSH levels in patients with PTC were close to the age-
specific distribution of TSH found in people living in
iodine sufficient areas, as reported in the NHANES III
survey (Hollowell et al. 2002,Aoki et al. 2007,Surks
& Hollowell 2007). These data strongly suggest that in
our series of patients, the higher levels of TSH in PTC
with respect to BTND are not due to an increase of
thyrotropin in patients with thyroid cancer, but are
mainly related to the reduction of serum TSH in
patients with nodular goiter. In agreement with this
hypothesis a significant age-dependent development of
thyroid autonomy (TSH below 0.4 mU/ml) was
observed in BTNDs, but not in PTC. When patients
were considered separately, according to their clinical
diagnosis, in patients with benign thyroid disease the
prevalence of thyroid autonomy was significantly
higher in MNG than in S/I (Fig. 4A). In MNG, thyroid
autonomy seems to play a protective role in the
development of PTC, the prevalence of PTC in patients
with TSH !0.4 mU/ml being significantly lower than
in patients with no evidence of thyroid autonomy
(P!0.0001). On the other hand, in S/I the frequency of
PTC in patients with thyroid autonomy was lower
(5.3%) with respect to those with normal TSH levels
(7.6%), but this difference did not reach statistical
significance (c
2
,PZ0.09). However, the relatively
small number of patients with PTC and thyroid
autonomy in the S/I group may account for the lack
of statistical significance. Further studies are needed to
clarify this point. In this regard, Ngan et al. (2009) have
Figure 6 Box-whisker plot illustrating median, quartiles, and
ranges of TSH levels according to the presence of anti-thyroid
antibodies (TAb). TSH levels in PTC (gray box) were
significantly higher than in BTND (white box) both in TAb
positive patients and in subjects with no detectable TAb
(Mann–Whitney test, P!0.01).
Endocrine-Related Cancer (2009) 16 1251–1260
www.endocrinology-journals.org 1257

found germline mutations of the TTF1 gene in a
subgroup of patients with MNG, and that mutations of
this gene are not present in patients without history of
MNG and in healthy subjects. In addition, Gudmunds-
son et al. (2009) have shown that variants on specific
loci (9q22.33 and 14q13.3) are associated with
increased risk of papillary and follicular thyroid cancer
and both alleles are associated with lower TSH levels in
the general population. Interestingly, the gene located
at the 14q13.3 locus is TTF1. These observations
suggest that a different genetic background may be
present in PTC patients with MNG and that specific
mutations may allow PTC to growth in patients
with low serum TSH levels. In our study group
the prevalence of PTC in patients with serum TSH
!0.4 mU/ml was significantly lower than in patients
with no evidence of thyroid autonomy in MNG, but our
data did not allow us to draw a definitive conclusion in
patients with S/I nodules. We hypothesize that the
development of thyroid autonomy, by reducing TSH
levels, reduces the probability that mutated oncogenes
may cause cancer clinically detectable. Most common
mutations in papillary carcinomas are point mutations
of the BRAF gene and RET/PTC rearrangement. These
genetic alterations are found in more than 70% of
papillary carcinomas and they rarely overlap in the
same tumor (Ciampi & Nikiforov 2007,Nikiforova &
Nikiforov 2008). It is also widely recognized that PTC
needs TSH to progress and become clinically evident.
In this respect, it is important to underscore that the
medical treatment of differentiated thyroid cancer has
been based on the use of L-T
4
to reduce serum TSH
levels (Mazzaferri & Jhiang 1994,Mazzaferri 1999,
Sipos & Mazzaferri 2008). It is thus possible to
hypothesize that the development of thyroid autonomy,
by reducing TSH levels, may represent a form of ‘self-
treatment’, at least in patients living in relatively
iodine deficient areas such as those considered in the
present study. This phenomenon may be less relevant
in iodine sufficient areas.
The hypothesis that TSH is involved in the
progression of PTC is further supported by the
observation that higher TSH levels are associated
with a more advanced cancer stage, as reported by
Haymart et al. (2008b). In our series, in agreement with
the results reported by Haymart et al. when patients
with PTC were grouped according to TNM, signi-
ficantly higher TSH values were observed in patients
in T3–T4 with respect to those in T1–T2. A similar
finding was present in patients with neck node
metastasis with respect to those with no evidence of
node metastasis.
In this work, we have also analyzed the relationship
between the presence of humoral thyroid autoimmu-
nity and TSH levels in patients with PTC. The
relationship between thyroid autoimmunity and PTC
has been suggested in many studies, but its meaning is
still uncertain (Dailey et al. 1955,Hirabayashi &
Lindsay 1965,Holm et al. 1985,Walker & Paloyan
1990,Baker 1995,Okayasu et al. 1995). Our data show
that TSH is significantly higher in TAb positive than in
TAb negative patients, suggesting that TAb positivity
is the expression of a mild autoimmunity that may
affect thyroid function. Interestingly, Haymart et al.
(2008a), studying a large histological series of patients
with nodular thyroid diseases submitted to surgery,
have reported a significant association between
pathologic Hashimoto’s thyroiditis and higher TSH
levels. In this work, pathologic Hashimoto’s thyroiditis
was detected in 20.6% of patients with DTC and 19.8%
of patients with benign thyroid diseases (PZ0.4). In
our series of patients, the frequency of PTC was not
significantly different between TAb positive and TAb
negative patients and serum TSH levels were signi-
ficantly higher in PTC than BTND both in TAb
positive and negative patients. This result supports the
hypothesis that humoral thyroid autoimmunity does
not play a significant role in the development of thyroid
cancer.
In conclusion, we have confirmed that a significant
difference between serum TSH levels is present in
patients with PTC and BTNDs. We have shown that
this difference is mainly due to the reduction of TSH
observed in patients with nodular goiter and is not
related to thyroid autoimmunity. We hypothesize that
the development of thyroid autonomy may account for
the lower TSH levels in patients with goiter, while in
PTC serum TSH levels are closer to the value of
thyroid disease free population. We suggest that the
possible mechanism underling these clinical obser-
vations is that thyroid autonomy, by reducing TSH
levels, may slow down cancer progression and reduce
the probability that mutated oncogenes may cause
clinically detectable cancer. These observations may
be relevant for the inclusion of thyroid function as one
of the clinical parameters to consider in the evaluation
of the risk of PTC in patients with nodular thyroid
diseases.
Declaration of interest
The authors declare that there is no conflict of interest that
could be perceived as prejudicing the impartiality of the
research reported.
E Fiore et al.: TSH and risk of PTC
www.endocrinology-journals.org1258

Funding
This work was supported by the Italian ‘Ministero
dell’Universita
`e della Ricerca Scientifica’ (MURST),
research program (grant number 2007 RJ7AP8): protein,
metabolomic, fingerprint and gene expression profile of
thyroid nodules with follicular proliferation cytology:
identification of new marker to distinguish benign and
malignant thyroid nodules.
References
Aghini-Lombardi F, Antonangeli L, Martino E, Vitti P,
Maccherini D, Leoli F, Rago T, Grasso L, Valeriano R,
Balestrieri A et al. 1999 The spectrum of thyroid disorders
in an iodine-deficient community: the Pescopagano
survey. Journal of Clinical Endocrinology and
Metabolism 84 561–566.
Aoki Y, Belin RM, Clickner R, Jeffries R, Phillips L &
Mahaffey KR 2007 Serum TSH and total T
4
in the United
States population and their association with participant
characteristics: National Health and Nutrition
Examination Survey (NHANES 1999–2002). Thyroid
17 1211–1223.
Baker JR Jr 1995 The immune response to papillary thyroid
cancer. Journal of Clinical Endocrinology and
Metabolism 80 3419–3420.
Biondi B, Filetti S & Schlumberger M 2005 Thyroid-
hormone therapy and thyroid cancer: a reassessment.
Nature Clinical Practice. Endocrinology & Metabolism
132–40.
Boelaert K, Horacek J, Holder RL, Watkinson JC,
Sheppard MC & Franklyn JA 2006 Serum thyrotropin
concentration as a novel predictor of malignancy in
thyroid nodules investigated by fine-needle aspiration.
Journal of Clinical Endocrinology and Metabolism
91 4295–4301.
British Thyroid Association, Royal College of Physicians
2007 Fine-needle aspiration cytology. In Report of
the Thyroid Cancer Guidelines Update Group, edn 2,
pp 9–10. Ed P Perros. London: Royal College of
Physicians.
Ciampi R & Nikiforov YE 2007 RET/PTC rearrangements
RAF mutations in thyroid tumorigenesis. Endocrinology
148 936–941.
Dailey ME, Lindsay S & Skahen R 1955 Relation of thyroid
neoplasms to Hashimoto disease of the thyroid gland.
A.M.A. Archives of Surgery 70 291–297.
Davies L & Welch HG 2006 Increasing incidence of thyroid
cancer in the United States, 1973–2002. Journal of the
American Medical Association 295 2164–2167.
Fenzi GF, Ceccarelli C, Macchia E, Monzani F, Bartalena L,
Giani C, Ceccarelli P, Lippi F, Baschieri L & Pinchera A
1985 Reciprocal changes of serum thyroglobulin and TSH
in residents of a moderate endemic goitre area. Clinical
Endocrinology 23 115–122.
Gudmundsson J, Sulem P, Gudbjartsson DF, Jonasson JG,
Sigurdsson A, Bergthorsson JT, He H, Blondal T, Geller F,
Jakobsdottir M et al. 2009 Common variants on 9q22.33
and 14q13.3 predispose to thyroid cancer in European
populations. Nature Genetics 41 460–464.
Haymart MR, Glinberg SL, Liu J, Sippel RS, Jaume JC &
Chen H 2008aHigher serum TSH in thyroid cancer
patients occurs independent of age and correlates with
extrathyroidal extension. Clinical Endocrinology
[in press].
Haymart MR, Repplinger DJ, Leverson GE, Elson DF,
Sippel RS, Jaume JC & Chen H 2008bHigher serum
thyroid stimulating hormone level in thyroid nodule
patients is associated with greater risks of differen-
tiated thyroid cancer and advanced tumor stage.
Journal of Clinical Endocrinology and Metabolism
93 809–814.
Hirabayashi RN & Lindsay S 1965 The relation of thyroid
carcinoma and chronic thyroiditis. Surgery, Gynecology
and Obstetrics 121 243–252.
Hollowell JG, Staehling NW, Flanders WD, Hannon WH,
Gunter EW, Spencer CA & Braverman LE 2002
Serum TSH, T(4), and thyroid antibodies in the United
States population (1988 to 1994): National Health and
Nutrition Examination Survey (NHANES III).
Journal of Clinical Endocrinology and Metabolism
87 489–499.
Holm LE, Blomgren H & Lowhagen T 1985 Cancer risks in
patients with chronic lymphocytic thyroiditis. New
England Journal of Medicine 312 601–604.
Hundahl SA, Fleming ID, Fremgen AM & Menck HR 1998
A National Cancer Data Base report on 53,856 cases of
thyroid carcinoma treated in the U.S., 1985–1995 (see
comments). Cancer 83 2638–2648.
Jonklaas J, Nsouli-Maktabi H & Soldin SJ 2008
Endogenous thyrotropin and triiodothyronine concen-
trations in individuals with thyroid cancer. Thyroid
18 943–952.
Mazzaferri EL 1991 Treating differentiated thyroid carci-
noma: where do we draw the line? Mayo Clinic
Proceedings 66 105–111.
Mazzaferri EL 1999 An overview of the management
of papillary and follicular thyroid carcinoma. Thyroid
9421–427.
Mazzaferri EL & Jhiang SM 1994 Long-term impact of
initial surgical and medical therapy on papillary and
follicular thyroid cancer. American Journal of Medicine
97 418–428.
Mazzaferri EL & Young RL 1981 Papillary thyroid
carcinoma: a 10 year follow-up report of the impact of
therapy in 576 patients. American Journal of Medicine
70 511–518.
Ngan ES, Lang BH, Liu T, Shum CK, So MT, Lau DK,
Leon TY, Cherny SS, Tsai SY, Lo CY et al. 2009
A germline mutation (A339V) in thyroid transcription
Endocrine-Related Cancer (2009) 16 1251–1260
www.endocrinology-journals.org 1259

factor-1 (TITF-1/NKX2.1) in patients with multinodular
goiter and papillary thyroid carcinoma. Journal of the
National Cancer Institute 101 162–175.
Nikiforova MN & Nikiforov YE 2008 Molecular genetics of
thyroid cancer: implications for diagnosis, treatment and
prognosis. Expert Review of Molecular Diagnostics
883–95.
Okayasu I, Fujiwara M, Hara Y, Tanaka Y & Rose NR 1995
Association of chronic lymphocytic thyroiditis and
thyroid papillary carcinoma. A study of surgical cases
among Japanese, and white and African Americans.
Cancer 76 2312–2318.
Polyzos SA, Kappaita M, Efstathiadou Z, Poulakos P,
Slavakis A, Sofianou D, Flaris N, Leontsini M, Kourtis A
& Avramidis A 2008 Serum thyrotropin concentration as
a biochemical predictor of thyroid malignancy in patients
presenting with thyroid nodules. Journal of Cancer
Research and Clinical Oncology 134 953–960.
Sipos JA & Mazzaferri EL 2008 The therapeutic manage-
ment of differentiated thyroid cancer. Expert Opinion on
Pharmacotherapy 92627–2637.
Sobin L 2002 UICC TNM Classification of Malignant
Tumours. New York: Wiley Liss.
Surks MI & Hollowell JG 2007 Age-specific
distribution of serum thyrotropin and antithyroid
antibodies in the US population: implications for the
prevalence of subclinical hypothyroidism. Journal of
Clinical Endocrinology and Metabolism
92 4575–4582.
The Papanicolaou Society of Cytopathology Task Force on
Standards of Practice 1996 Guidelines of the Papanico-
laou Society of Cytopathology for the examination of
fine-needle aspiration specimens from thyroid nodules.
Diagnostic Cytopathology 15 84–89.
Vitti P, Mariotti S, Marcocci C, Chiovato L, Giachetti M,
Fenzi G & Pinchera A 1990 Thyroid autoimmunity
and thyroid autonomy. Acta Medica Austriaca
17 90–92.
Walker RP & Paloyan E 1990 The relationship between
Hashimoto’s thyroiditis, thyroid neoplasia, and primary
hyperparathyroidism. Otolaryngologic Clinics of North
America 23 291–302.
E Fiore et al.: TSH and risk of PTC
www.endocrinology-journals.org1260