Effect of Thyroid Hormone Levels on Glycemic Control: The Indian Context

Objective: Diabetes mellitus (DM) is known as the silent pandemic. It is hypothesized that other endocrine systems are affected by the metabolic changes occurring due to DM. We aimed to investigate the correlation of thyroid hormones with glycaemic and lipid parameters. Materials and Methods: ۸۱ diabetic patients and ۸۱ non-diabetic age and sex-matched healthy volunteers participated in the study. Their blood samples were analysed for fasting blood glucose (FBG), glycosylated haemoglobin (HbA۱C), total tri-iodothyronine (T۳), total thyroxine (T۴), free T۳ (FT۳), free T۴ (FT۴), thyroid-stimulating hormone (TSH), total cholesterol (CHOL), High-Density-Lipoprotein cholesterol (HDLC) and Low-Density-Lipoprotein cholesterol (LDLC). Data was analysed using appropriate statistical tests. Results: Among the cases, ۷۰.۳۷% were euthyroid, while ۲۴.۷% had subclinical hypothyroidism, ۲.۴۷% had clinical hypothyroidism, ۱.۲۳% had subclinical and ۱.۲۳% had clinical hyperthyroidism. FBG, HbA۱c and TSH (P< ۰.۰۵) were significantly higher in diabetics compared to controls. On the other hand, T۳, FT۳, FT۴, and HDLC (P< ۰.۰۵) were significantly lower in diabetics compared to controls. A significant negative correlation (P< ۰.۰۵) was found when T۳ and FT۳ were compared against age, FBG and HbA۱c. A significant positive correlation (P< ۰.۰۵) was found when T۳ and FT۳ were compared against HDLC, LDLC & CHOL. Conclusion: Our statistics show that high-normal levels of T۳ and FT۳ are correlated with lower levels of FBG and HbA۱c, hence improved glycaemic control. We recommend that thyroid profile of diabetic patients with poor control should be monitored regularly. Early detection of thyroid dysfunction and initiation of therapy for it, can improve the treatment outcome of hypoglycaemic drugs.

Keywords:

Thyroid hormones , Hypothyroidism , Diabetes mellitus , Glycated haemoglobin A