Association Between Subclinical Hypothyroidism and HbA1c Levels in Non-Diabetic Patients: A Case-Control Study

Abstract

Diabetes mellitus (DM) is a chronic endocrine disorder. Previous studies have indicated a potential connection between subclinical hypothyroidism (SH), insulin resistance, and altered blood sugar levels. This study aimed to compare HbA1c levels between nondiabetic individuals with SH and healthy controls with normal thyroid function. A case-control study was conducted with 200 participants, including those with SH and healthy controls (HCs). Serum levels of thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), HbA1c, and fasting plasma glucose were measured. Statistical analysis was performed to assess the differences between the groups and the correlation between HbA1c and TSH, and T3 and T4. Significant differences were observed in the mean HbA1c (P=0.0002) and TSH (p = 0.0001) levels between the control and SH groups. However, no significant differences were found in the mean age of fasting plasma glucose FBG, T3, and T4 levels between the groups. HbA1c levels were positively correlated with serum TSH levels (r=0.684, P<0.00001). In conclusion, our study identified a significant positive correlation between HbA1c and TSH levels in individuals with subclinical hypothyroidism. Therefore, assessing HbA1c levels in patients with hypothyroidism may be crucial for diagnosing diabetes or prediabetic states.