Effect Of Thyroid Hormone On Islet Function In Hospitalized Patients With Type 2 Diabetes Mellitus Complicated With Subclinical Hypothyroidism

Objective:To investigate the relationship between subclinical hypothyroidism and insulin resistance in patients with type 2 diabetes mellitus,and to observe the changes of insulin resistance and islet function in patients with type 2 diabetes mellitus complicated with subclinical hypothyroidism after thyroid hormone replacement therapy.Methods:A total of 157 patients with type 2 diabetes admitted to the Department of Endocrinology,Shanxi Provincial People’s Hospital from February 2019 to December2020 were included in this study,including 54 patients with euthyroidism,52 patients with mild subclinical hypothyroidism(SCH)(4.2 < TSH < 10.0 u IU/mL),and 51 patients with severe SCH(TSH ≥ 10.0 u IU/mL).In the euthyroid control group,patients with severe SCH were treated with thyroid hormone replacement therapy,and patients with mild SCH were treated with placebo.General biochemical parameters were measured in all patients before and 24 weeks after enrollment.Results:1.Compared with enrollment,glycosylated hemoglobin(Hb A1c)levels were decreased in the normal thyroid function group(P < 0.05),and fasting C-peptide,ln(HOMA2-% β),and ln(HOMA2-IR)were not significantly changed(P > 0.05)in the normal group;fasting C-peptide,ln(HOMA2-% β),and ln(HOMA2-IR)were significantly increased in the mild SCH group compared with enrollment(P < 0.05);fasting C-peptide and ln(HOMA2-IR)levels were significantly decreased in the severe SCH group after thyroid hormone replacement therapy,and the differences were statistically significant(P < 0.05).2.The increase of fasting C-peptide and ln(HOMA2-% β)in the mild SCH group was more significant than that in the normal thyroid function group(P < 0.05),and the increase of ln(HOMA2-IR)in the mild SCH group was more significant than that in the normal thyroid function group(P < 0.01).3.The levels of fasting C-peptide,ln(HOMA2-% β)and ln(HOMA2-IR)in the severe SCH group were significantly lower than those in the normal thyroid function group(P < 0.01).Conclusion:1.Insulin resistance is more severe in the subclinical hypothyroidism group than in the normal thyroid function group,and subclinical hypothyroidism can aggravate insulin resistance in patients with type 2 diabetes.2.Thyroid hormone can reduce insulin resistance and protect islet function in patients with type 2 diabetes and subclinical hypothyroidism.3.BMI,FT3,TSH,FPG,fasting C-peptide,and TG were positively correlated with HOMA2-IR.4.The possible specific cut-point of TSH for predicting insulin resistance in patients with type 2 diabetes is 6.245 u IU/mL.