Free thyroxine is an independent predictor of subcutaneous fat in euthyroid individuals.
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.


METHODS
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 SF 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.
Alevizaki
Maria
M
Endocrine Unit, Department of Endocrinology and Metabolism, Evgenidion Hospital, Athens, Greece. dag.hofso@siv.no
Saltiki
Katerina
K
Voidonikola
Paraskevi
P
Mantzou
Emily
E
Papamichael
Christos
C
Stamatelopoulos
Kimon
K
D050154:Adiposity / Q000502:physiology; D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology; D008875:Middle Aged; D050177:Overweight / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D011379:Prognosis; D050151:Subcutaneous Fat / Q000378:metabolism*; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000502:physiology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood*
D013972:Thyrotropin; D013974:Thyroxine