Low Free T₃ was Associated with Poor Glycemic Control in Type 2 Diabetes in a Hospital Based Study in Bangladesh.

Clinical significance of low free T₃ (FT₃) has not been well explained in patients with type 2 diabetes mellitus (T2DM); FT₃ level may be associated with diabetes control and also with diabetic complications. This cross-sectional study was carried out among 153 (mean age 46.8±12 years; female 68%, mean duration of diabetes 5.5±0.53 years, 63.4% either overweight or obese) non-pregnant adults with T2DM who had no acute illness and were unaware about their thyroid function status from July 2016 to December 2016. Serum TSH, free T₄ (FT₄) and FT₃ were measured in all patients by radioimmunoassay (RIA). Patients having subnormal FT₃ level with normal TSH and FT₄ levels were labeled as having low FT₃ syndrome. The mean HbA1c of the study subjects was 8.3±1.7%, serum TSH 2.24±0.34μIU/mL, FT₄ 16.5±6.56fmol/mL and FT₃ was 5.36±1.74fmol/mL. Among them, 9.15% were found to have low FT₃ syndrome. There was no statistical difference of FT₃ level between males and females (5.87±1.50 vs. 5.99±1.85fmol/mL, mean±SD; p=0.165) and among different BMI groups (p=0.179). Patients with uncontrolled diabetes had lower FT₃ than those with controlled diabetes (5.91±1.83 vs. 6.15±1.21fmol/mL, mean±SD, p=0.024). The frequency of low FT₃ syndrome was 11.1% in uncontrolled diabetic patients whereas none of the patients with controlled diabetes had low FT₃. FT₃ level showed positive correlations with the duration of diabetes (r=0.296, p=0.002) and FT₄ level (r=0.490, p<0.001) only in female subjects. A fair number of clinically stable T2DM patients had low FT₃ in our study. Patients with uncontrolled diabetes had lower FT₃ than those with controlled diabetes.