RESUMO
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.
