Trunk fat and leg fat in relation to free triiodothyronine in euthyroid postmenopausal women

Abstract

Background: A high level of free triiodothyronine (FT3) within the referen ce range may be a potential metabolic risk marker. However, the relationship between different fat depots and FT3 has remained unclear. Objective: We aimed to explore the relationships between segmental fat di stribution and FT3 in euthyroid middle-aged and elderly men and postmenopausal women. Methods: A total of 891 subjects (394 men and 497 women) were enrolled. A bioelectrical impedance analyzer was used to measure total, trunk, arm and le g fat mass (FM) and fat percentage (fat%). The leg fat mass to trunk fat mass ratio (LTR) was calculated to evaluate the relative distribution of leg fat compared with tha t of trunk fat. Thyroid hormones were measured by electrochemical luminescence immunoassay. Results: FT3 in men did not change significantly with increases in LTR q uartiles, while FT3 in women decreased significantly (P for trend = 0.004). In multivariate linear regression analysis, multiple metabolic and cardiovascular risk factors we re adjusted. The LTR was negatively related to FT3 in women (P < 0.05). After further mutual adjustment for trunk fat and leg fat parameters, trunk FM and fat% were positively r elated to FT3, while leg FM and fat% were negatively related to FT3 in women (all P < 0.05). Conclusions: In euthyroid postmenopausal women, trunk fat was positively co rrelated with FT3, whereas leg fat was negatively correlated with FT3. Our fin dings supported that a high level of FT3 within the reference range was related to adverse fat distribution.