Objective: The study investigated the association between free triiodothyronine (FT3) and poor glycemic control with different definitions in euthyroid patients with type 2 diabetes mellitus (T2DM).
Methods: This was a cross-sectional study which included 2172 patients from National Metabolic Management Center in Ruijin Hospital. The association between thyroid function and glycated hemoglobin A1c (HbA1c) was determined by multiple liner regression models. The association between FT3 and poor glycemic control was further determined by binary logistic regression models. Two definitions of poor glycemic control (HbA1c ≥ 7% and HbA1c ≥ 8%) were applied when we analyzed the association.
Results: Prevalence of HbA1c ≥ 7% and HbA1c ≥ 8% were 63.8% and 39.3%, respectively. After adjusting for confounding factors, FT3, rather than free tetraiodothyronine (FT4) or thyroid stimulating hormone (TSH), was independently associated with HbA1c (β = -0.104, P = 0.002). Further analysis after gender stratification showed that the association was only found in males (β = -0.164, P < 0.001). We further analyzed the association between FT3 quartiles and poor glycemic control. FT3 quartiles were not significantly associated with the risk of HbA1c ≥ 7% before and after adjusting for confounding factors in both genders. FT3 quartiles were negatively associated with the risk of HbA1c ≥ 8% only in males, independent of traditional risk factors for poor glycemic control (P for trend = 0.030).
Conclusions: FT3 in the reference range was significantly associated with reduced risk of HbA1c ≥ 8% in males, independent of traditional risk factors for poor glycemic control.
Keywords: Free triiodothyronine; Glycemic control; Type 2 diabetes mellitus.
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