Body mass and serum thyrotropin are positively
associated in normal subjects
(March 2006)
The background of the study. Some change in weight
is common in patients with hyperthyroidism or hypothyroidism, and
in normal subjects serum thyrotropin (TSH) concentrations may be
positively related to body weight. In this study, the relationship
between serum TSH and body-mass index was determined in a large
population-based cohort.
How the study was done. Weight, height, and serum
TSH were measured in 6164 adults living in Tromsø, Norway,
in 2001. Among them, 2672 had the same measurements in 1994-1995.
Only the subjects whose serum TSH concentrations were within the
2.5- to 97.5-percentile range were included, subdivided by smoking
status (approximately 25 percent were smokers).
The results of the study. Serum TSH concentrations
increased with age in women and men, smokers and nonsmokers, in
the 2001 cohort. Among nonsmokers, the mean serum TSH concentration
was 1.6 mU/L in women aged 30 to 39 years, and it was 2.3 mU/L in
those aged >69 years; the respective values in men were 1.6 and
2.3 mU/L. The increase with age was smaller in the smokers.
There was a gradual increase in body-mass index with increasing
serum TSH in both women and men. Among the nonsmoking women and
men, the body-mass index in those in the highest quartile for serum
TSH was 1.4 kg/m2 and 0.4 kg/m2 higher, respectively, than in those
in the lowest quartile for serum TSH; after adjustment for age,
only the difference in women was statistically significant. Considering
serum TSH as a continuous variable, serum TSH concentrations were
positively associated with body-mass index in both women and men
who were nonsmokers (P<0.01 and P<0.05, respectively). In
the smokers, body-mass index was not associated with either quartile
of serum TSH or serum TSH as a continuous variable.
Among the 2672 subjects in whom serum TSH was measured in 1994-1995
and in 2001, 1725 had normal serum TSH values at both times and
no change in smoking status. There was no association between the
increase in body-mass index and the quartile of increase in serum
TSH between 1994-1995 and 2001.
The conclusions of the study. In women and men
who are nonsmokers, serum TSH concentrations are positively associated
with body-mass index.
The original article. Nyrnes A, Jorde R, Sundsfjord
J. Serum TSH is positively associated with BMI. Int J Obes (Lond)
2006;30:100-5.
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