Gu Y, et al. - Authors analyzed the role of serum thyroid hormones (THs) as predictive factors for the development of metabolic syndrome (MetS) in adults enrollees without a history of MetS, with a median follow-up duration of 2 years in Tianjin, China. The serum TH levels were estimated by the chemiluminescence immunoassay. Data displayed that the hazard ratios for MetS across serum free triiodothyronine (FT3) quintiles were 1.00, 1.03, 1.14, 1.09 and 1.33, respectively. Free thyroxine (FT4), TSH and MetS did not present with any significant correlations. Therefore, instead of FT4 and thyroid-stimulating hormone (TSH), increased serum FT3 level was discovered to be an independent predictor for developing MetS in euthyroid subjects.