Objective: Thyroid function parameters have been associated with
obesity, but associations with the type of adiposity have not been
examined. We used ultrasound (US) to assess regional adiposity and
investigated associations of thyroid function with parameters of central
obesity.
Design: Cross-sectional study.
Methods: A total of 303 apparently healthy individuals (age 42.9+/-8.8,
body mass index (BMI) 19.0-43.3, median 26.2 kg/m(2), 181 women) were
examined for indices of the metabolic syndrome. BMI, waist and hip
circumference, abdominal subcutaneous fat (SF), and preperitoneal fat
(PF) layer was estimated. TSH, free thyroxine (fT(4)), triiodothyronine
(T-3), thyroid autoantibodies, insulin, glucose, and lipid levels were
measured. Subjects receiving T-4 (9.2%) were excluded.
Results: SF and SF/PF ratio were inversely correlated with fT(4) levels
(r=-0.169. P=0.023, r=-0.193, P=0.009 respectively). In multivariate
analysis, fT(4) was a predictor of SF and SF/PF, independently of age,
sex, and smoking. SF correlated with TSH levels (r=0.149, P=0.037). PF
and SF were positively associated with T-3 levels (r=0.245, P=0.004 and
r=0.189, P=0.019 respectively). T-3 levels were positively associated
with BMI (r=0.257, P=0.0004). waist perimeter (r=0.324, P<0.0001), and
waist-to-hip ratio (WHR; r=0.363, P<0.0001). The T-3/fT(4) ratio was
positively correlated with SF (r=0.182, P=0.028), WHR (r=0.267,
P=0.0003), and BMI (r=0.146, P=0.043).
Conclusions: Increasing SI, accumulation as assessed by US is associated
with lower fT(4) and higher TSH levels among euthyroid slightly
overweight individuals. These associations indicate that subtle
variation in thyroid function may participate in regional adiposity
