Obesity and thyrotropinemia.

Abstract

To study the relation between body mass index (BMI) and TSH in euthyroid and subclinical hypothyroid obese children and compared serum TSH level among obese and overweight children.
Fifty consecutive children (aged 2-18 yr) presenting for obesity were studied. All cases with TSH > 10, low T3/T4, organic and syndromic obesity were excluded. Patients were divided into Group 1: Overweight (n=20) (BMI between 85(th) to 95(th) centile) and Group 2: Obesity (n=30) (BMI > 95(th) centile). Fisher's exact test, Mann-Whitney U test and Pearson's correlation were used for statistical analysis. P value < 0.05 was considered significant.
Elevated TSH level (between 4.5-10 mIU/L) with normal T3, T4 was seen in 4/20 overweight and 9/30 of obese children (P=0.5219). The mean TSH was comparable in both the groups (3.22 +/- 3.1 mIU/L vs. 3.63 +/- 2.2 mIU/L, P=0.3491). Overall TSH showed no correlation with BMI (r= 0.0014, P=0.9924).
The preliminary data did not show any relation between severity of obesity and TSH level. Further large scale data from population are required to confirm these findings.

Full text

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Correspondence and Reprint requests : Dr K.V.S. Hari Kumar, MD,
Department of Endocrinology, Medwin Hospitals, Nampally,
Hyderabad. AP.-500001, India.
[DOI- -10.1007/s12098- -009- -0153- -7]
[Received July 10, 2008; Accepted August 20, 2008]
Original Article
Obesity and Thyrotropinemia
K.V.S. Hari Kumar, A. Verma, J. Muthukrishnan and K.D. Modi
Department of Endocrinology, MEDWIN Hospitals, Hyderabad, AP, India
ABSTRACT
Objective. To study the relation between body mass index (BMI) and TSH in euthyroid and subclinical hypothyroid obese
children and compared serum TSH level among obese and overweight children.
Methods. Fifty consecutive children (aged 2-18 yr) presenting for obesity were studied. All cases with TSH > 10, low T3/T4,
organic and syndromic obesity were excluded. Patients were divided into Group 1: Overweight (n=20) (BMI between 85th to
95th centile) and Group 2: Obesity (n=30) (BMI > 95th centile). Fisher’s exact test, Mann-Whitney U test and Pearson’s
correlation were used for statistical analysis. P value < 0.05 was considered significant.
Results. Elevated TSH level (between 4.5 – 10 mIU/L) with normal T3, T4 was seen in 4/20 overweight and 9/30 of obese
children (P=0.5219). The mean TSH was comparable in both the groups (3.22 ± 3.1 mIU/L vs. 3.63 ± 2.2 mIU/L, P=0.3491).
Overall TSH showed no correlation with BMI (r= 0.0014, P=0.9924).
Conclusion. The preliminary data did not show any relation between severity of obesity and TSH level. Further large scale
data from population are required to confirm these findings. [Indian J Pediatr 2009; 76 (9) : 933-935]E-mail : hariendo@
rediffmail.com
Key words : Hypothyroidism; Obesity; Thyrotropinemia; Children
Obesity amongst children and adolescents has become
an issue of major public health concern in our country.1
The estimated prevalence of overweight is about 15-18%
and obesity about 2-4% amongst Indian children. 2,3
Although the prevalence of obesity is lower than that in
Western children, our body composition, higher and
central location of body fat makes them more prone to
significant morbidity. 4 The commonest laboratory
evaluation in obese children includes thyroid function
tests in general practice. Mild elevation of TSH in
obesity is widely reported in literature and this
constitutes a reason for referral to endocrinology clinic.
Guidelines regarding thyroxine replacement exist for
adult population in subclinical hypothyroidism, but it
is controversial in children. 5,6
Obesity often coexists with hypothyroidism as a
cause or consequence of it. Thyroid hormones are
potent regulators of thermogenesis, basal and total
energy consumption.7 Obesity affects hypothalamic-
pituitary-thyroid axis directly or indirectly leading to
alterations in thyroid function tests. The commonest
observed change is elevation in TSH and also of
triiodothyronine (T3) and thyroxine (T4) hormones.8
Though TSH elevation with obesity is widely accepted,
the data is conflicting regarding the changes in TSH
with weight loss in obese children. Few studies have
reported fall in TSH with weight loss whereas others
did not show this reversal.9,10 Thus it appears that body
weight is a major determinant of level of serum TSH
and it is not apparent from existing literature about the
linear correlation between these two variables.11
Therefore we studied the relation between body mass
index (BMI) and TSH in euthyroid and subclinical
hypothyroid obese children and compared serum TSH
level among obese and overweight children.
MATERIALS AND METHODS
We studied 50 children and adolescents (aged between
2-18 yr) attending the obesity clinic at our hospital. A
detailed history was taken regarding the socioeconomic
status, family history of thyroid illness, dietary habits,
duration of outdoor physical activity and relevant
menstrual history in female patients. Detailed clinical
examination was done including anthropometry, pubertal
Indian Journal of Pediatrics, Volume 76—September, 2009933

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K.V.S. Hari Kumar et al
934 Indian Journal of Pediatrics, Volume 76—September, 2009
status assessment, presence of goiter, acanthosis and
any systemic features suggestive of syndromic obesity.
Thyroid hormones (TSH, Total T3 and T4) were
determined in all the children. Thyroid function tests
were done by enzyme linked immuno-sorbant assay and
intra- and interassay variations were less than 10%. The
reference values considered as normal as per local
laboratory were given as follows: TSH (0.25-4.5 mIU/L),
T3 (70-200 ng/dL) and T4 (5-12 mg/dL).
Body mass index (BMI) was calculated as the weight in
Kg divided by square of the height in meters. Obesity was
defined as BMI more than 95th centile according to the
BMI specific for age and sex chart of Indian children.
Reference data was taken from Indian population as
provided by Agarwal KN et al and proposed by Indian
Academy of Pediatrics.12 Overweight was defined as BMI
between 85th to 95th centile on the same chart. Patients
with TSH between 4.5 – 10 mIU/L, alongwith normal
total T3 and T4 were considered to have subclinical
hypothyroidism and included in the analysis. Patients
with serum TSH more than 10 mIU/L were considered to
have overt hypothyroidism and excluded from the study.
Smokers and children taking any medication likely to
affect the weight and thyroid hormones including
corticosteroids, estrogen preparations, antiepileptic drugs
were excluded. Children with other possible endocrine or
metabolic disorders were excluded from the study. The
patients were subdivided into two groups for analysis;
Group 1: Overweight children (n=20) and Group 2: Obese
children (n=30).
Summary data are expressed as mean ± SD and
comparison between groups was done by non parametric
Mann-Whitney U test. Fisher’s exact test (two by two
tables) was used to compare frequency of variables
among two groups and relationship between BMI and
TSH in an overall study population was done by
Pearson’s correlation analysis. A probability value of less
than 0.05 was considered to be statistically significant.
RESULTS
The clinical and biochemical data of the study population
was summarized in table 1. The overall mean age of the
children was 13.2 ± 3.34 yr (range 6.4 to 18 yr). Females
were more in overweight group and the sex ratio was
similar in obese children. Subclinical hypothyroidism
was present in 4/20 overweight patients and in 9/30
obese children. Mean TSH was not significantly
different between the groups (3.22 ± 3.1 mIU/L vs. 3.63
± 2.2 mIU/L, P=0.1479). Serum TSH level did not show
correlation with BMI in entire study population as
demonstrated in fig. 1.
TABLE 1. Clinical and Biochemical Characteristics of Study
Population
FeatureGroup 1
(Overweight)
Group 2
(Obesity)
P value
Number
Age (yr)
Sex (M/F)
BMI (Kg/m2)
TSH (mIU/L)
Subclinical Hypothyroidism
2030
12.8 ± 3.2
6/14
22.45 ± 2.37
3.22 ± 3.12
4/20
13.4 ±3.45
15/15
30.28 ± 6.68
3.63 ± 2.24
9/30
0.3714
0.7208
<0.0001
0.1479
0.5219
Fig. 1. Correlation between BMI and TSH in Study population.
DISCUSSION
In the present study we studied the relation between
severity of obesity (as defined by BMI into overweight
and obesity) and level of TSH in children and adolescents.
The clinical profile was similar at presentation in both
overweight and obese groups. Prevalence of subclinical
hypothyroidism was more in obese children (30%) than
overweight children (20%) but the observed difference
was not statistically significant (P=0.5219). TSH values
were similar in both the groups and did not show any
correlation with BMI. To the author's knowledge this is
the first study comparing the TSH elevation between
overweight and obese children. Previous studies have
demonstrated elevation in serum TSH value in obese
children when compared with normal weight
children.8,13,14 However there is no data available
regarding the severity of obesity and TSH level.
Association of obesity and thyroid dysfunction is a
matter of controversy for several years.15 Obesity has
direct and indirect effects on hypothalamic-pituitary-
thyroid axis resulting in elevation of TSH level. Obese
individuals have more adipose tissue and leptin
production. Leptin directly stimulates thyrotropin
releasing hormone (TRH) neurons in the paraventricular
nucleus causing increased TSH level.16,17 However, in a
previous study in children, thyroid hormones did not
correlate significantly with leptin concentration.10 The
same study had showed that TSH was elevated in obese
chidren but did not decrease significantly with weight
loss. Our data also supports that increased body

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Obesity and Thyrotropinemia
Indian Journal of Pediatrics, Volume 76—September, 2009 935
weight results in TSH elevation and it has no relation to
severity of obesity (r = 0.0014, P= 0.9924).
The prevalence of elevated TSH was seen in about 1 –
21% of obese children and adolescents in previous
observational studies.13,14,18 The studies by Bhowmick et al
and Stichel H et al had taken TSH level more than 4 mIU/
L as suggestive of hypothyroidism and studied about 300
children each. The present data showed a prevalence of
30% of elevated TSH in obese children. This increased
prevalence could be due to small sample size and referral
bias of the sample to an obesity & thyroid clinic which
may not represent the obesity in general population. The
normal reference range for thyroid hormones in Indian
children was established recently.19 The mean serum was
TSH 2.57-3.6 mIU/L for boys and 1.83-3.58 mIU/L for
girls and the 97th percentile was in the range 6.01-8.4
mIU/L for boys and 5.28-8.04 mIU/L for girls in the
reference Indian population. This suggests that the upper
limit of normal TSH is up to 8.4 mIU/L in the present
population. In our study, we defined TSH > 4.5 mIU/L
with normal T3 and T4 as subclinical hypothyroidism.
Thus, the increased prevalence of hypothyroidism in the
present data could also be due to the fact that TSH cut off
used was not representative of population.
There is a controversy about requirement of thyroxine
replacement in children
hyperthyrotropinemia.6,9 Reinehr T et al studied about 240
obese chidren and demonstrated that TSH concentrations
were significantly higher in obese children and a
subgroup with substantial weight loss on follow up
showed a significant reduction of TSH.9 Thus it is
recommended that the elevation of TSH seems to be
rather a consequence of obesity than a cause of obesity.
Eliakim A et al have demonstrated that there were no
beneficial effects of thyroxine replacement in obese
children with thyrotropinemia.6
with isolated
The limitations of the present study were small sample
size and nonavailability of thyroid peroxisomal antibody
results. The authors did not exclude patients with family
history of obesity or thyroid illness and did not consider
the influence of socioeconomic status on obesity. Other
limitations are lack of comparison of thyroid function in
obese or overweight children with age matched normal
weight children and lack of follow up data from the study
population to observe the changes in thyroid hormones.
CONCLUSION
The present data reveals that elevation in serum TSH is
not related to the severity of underlying obesity. The
elevation of TSH in obese individuals does not appear
to be on a continuous scale. Further large scale
population data are required to confirm these findings.
Contributions: KVS and KDM: concept, design, data
collection, analysis, manuscript draft; JM: initial drafting and
statistical analysis; AV: data collection and analysis. The final
version of manuscript was seen and approved by all authors.
Conflict of Interest : None
Role of Funding Source : None
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