Background: Diabetes mellitus [DM] and thyroid dysfunction are the most commonly coexistent disorders. Hypo- and hyperthyroidism are causes of dysglycemia. However, the relation between normal thyroid hormone levels and insulin resistance [IR] is unclear.
The aim of the work: This study aimed to examine the association between the normal values of thyroid hormones and glucose metabolism and to investigate whether improvement of metabolic status can restore thyroid function in patients with uncontrolled type-2 diabetes mellitus [T2DM].
Patients and Methods: This study was a retrospective observational study. A total of 120 euthyroid participants were recruited. They were classified into four groups: Normal glucose tolerance [NGT, n =28], Prediabetes [n=32], well controlled DM [T2DM with glycated hemoglobin [HbA1c] ≤ 7%, n =26], and uncontrolled DM [T2DM with HbA1c > 7%, n = 34]. The results were compared between groups and the changes before and after treatment in uncontrolled DM group were observed and documented.
Results: A total sample of 120 participants showed that mean age of DM uncontrolled patients was 40.2± 19.5 and there were no significant differences among groups regarding their age, body mass index [BMI], blood pressure [BP]. However, groups showed significant differences regarding cholesterol, free t_4, serum glucose, two hours post prandial glucose, HbA1c, fasting insulin and insulin resistance. Regression analysis revealed that BMI, HbA1C, low density lipoprotein [LDL], triglycerides [TG] and total thyroxine [TT₄] had statistically significant association with insulin resistance. there is statistically significant difference between uncontrolled DM patients before and after treatment regarding HbA1C and glucose.
Conclusion: Reduced levels of free thyroid hormones [although in normal range] were significantly associated with high levels of serum glucose and HOMA-IR. There was significant improvement of blood glucose levels and insulin resistance.