Prevalence of Hypothyroidism in Patients with Type 2 Diabetes Mellitus - A Prospective Study

Background: Type 2 diabetes mellitus (T2DM) and thyroid dysfunction are both common endocrine disorders that frequently coexist and influence each other’s pathophysiology. This study aimed to determine the prevalence of hypothyroidism in patients with T2DM and evaluate its association with glycaemic parameters. Methods: A prospective observational study was conducted at a tertiary care hospital over 18 months. A total of 125 patients with confirmed T2DM were enrolled. Data collected included age, sex, BMI, duration of diabetes, fasting blood sugar (FBS), postprandial blood sugar (PPBS), random blood sugar (RBS), HbA1c, and thyroid function tests (TSH, T3, T4). Patients with known thyroid disease or secondary forms of diabetes were excluded. Results: The majority of patients were aged 51–60 years (52.0%), with 50.4% males and 49.6% females. Thyroid dysfunction was observed in 37.6% of patients, with 26.4% having subclinical hypothyroidism and 11.2% overt hypothyroidism. Elevated HbA1c (>6.5%) was present in 65.6% of patients. Significant positive correlations were noted between TSH and HbA1c (r = 0.312, p < 0.0001), FBS (r = 0.439, p < 0.0001), PPBS (r = 0.199, p = 0.026), and RBS (r = 0.200, p = 0.025). The prevalence of thyroid dysfunction increased with duration of diabetes, affecting 82.4% of those with >16 years of disease. Thyroid disorders were more frequent among patients with poor glycaemic control, as evidenced by HbA1c >6.5% (48.8% vs. 16.3%; p < 0.0001), FBS >111 mg/dL (44.6% vs. 30.0%; p = 0.042), PPBS >141 mg/dL (50.6% vs. 16.7%; p < 0.0001), and RBS >201 mg/dL (55.6% vs. 13.2%; p < 0.0001). Conclusion: Thyroid dysfunction, especially subclinical hypothyroidism, is common in T2DM and shows a significant association with poor glycaemic parameters and longer disease duration. Routine screening for thyroid abnormalities in diabetic patients is essential Key words: Type 2 diabetes mellitus, Hypothyroidism, Thyroid dysfunction, HbA1c, Body Mass Index Confidence Interval, Insulin Resistance & Hypertension