RESUMO
Objective Diabetes mellitus (DM) is often complicated by thyroid hormone abnormality. The aim of this study was to investigate the relationship between the thyroid hormone level and glycemic fluctuation in patients with euthyroid type 2 DM (T2DM).Methods A total of 143 euthyroid T2DM patients were treated in the Department of Endocrinology of Nanjing General Hospital from January 2014 to December 2015. The continuous blood glucose monitoring system was used for 72-hour continuous monitoring of blood glucose fluctuation indexes, including the standard deviation (SD) of the glucose level, the mean amplitude of glycemic excursions (MAGE), and the absolute mean of daily differences (MODD). According to the percentile of the MAGE level, the patients were divided into groups Q1 (MAGE<4.1864, n=35), Q2 (4.1864≤MAGE<5.3764, n=37), Q3 (5.3764≤MAGE<6.8484, n=35), and Q4 (MAGE≥6.8484, n=36), compared the thyroid hormone level and such thyroid function parameters as serum free triiodothyronine (FT3), triiodothyronine (T3), free thyroxine (FT4) and FT3/FT4 among the four groups, and analyzed the correlation between the thyroid hormone level and glycemic indexes.Results The levels of serum FT3, T3 and FT3/FT4 were decreased with the increase of MAGE (P<0.05), and those of FT3 and FT3/FT4 were 4.11±0.77 and 0.38±0.37 in group Q1, 4.06±0.55 and 0.34±0.37 in Q2, 3.49±0.57 and 0.33±0.06 in Q3, and 3.68±0.65 and 0.31±0.09 in Q4, with statistically significant differences between any two groups (P<0.05). There were also statistically significant differences among the four groups (P<0.05) in the T3 and FT4 levels (P<0.05). The levels of FT3 and T3 were correlated negatively with SD, MODD and MAGE (P<0.05), and so was that of FT3/FT4 with MAGE (r=-0.243, P<0.05).Conclusion MAGE reduces the levels of FT3 and FT3/FT4 in patients with euthyroid T2DM probably by inhibiting the conversion of T4 to T3.