Prevalence, Patterns, and Factors Associated with Thyroid Dysfunction among Adult Patients with Type 2 Diabetes Mellitus Attending a Tertiary Care Hospital: A Retrospective Record-Based Study

Abstract

Background: Thyroid dysfunction frequently coexists with type 2 diabetes mellitus (T2DM) and may adversely affect glycaemic control, lipid metabolism and vascular outcomes. However, thyroid abnormalities, particularly subclinical disorders, may remain clinically unrecognised among patients with T2DM. Objectives: To determine the prevalence and patterns of thyroid dysfunction and identify associated demographic, clinical and biochemical factors among adult patients with T2DM attending a tertiary-care hospital. Methods: A hospital-based retrospective record review was conducted in the Department of General Medicine at BGS Nagarur, Bengaluru, from April to July 2026. Medical records of 277 adults with T2DM and available thyroid-function test results were reviewed. Thyroid status was classified using serum thyroid-stimulating hormone and free thyroxine values. Descriptive statistics, chi-square test, independent-samples t-test, Mann Whitney U test and binary logistic regression were applied. Adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were reported. Results: Thyroid dysfunction was identified in 58 patients, corresponding to a prevalence of 20.9% (95% CI: 16.6–26.1%). Subclinical hypothyroidism was the predominant pattern (11.9%), followed by overt hypothyroidism (5.8%), subclinical hyperthyroidism (1.8%) and overt hyperthyroidism (1.4%). Of the affected patients, 56.9% had newly identified biochemical thyroid dysfunction. Thyroid dysfunction was significantly associated with female sex, higher body mass index (BMI), poor glycaemic control, dyslipidaemia and diabetic retinopathy. After adjustment, female sex (AOR: 2.04; 95% CI: 1.07–3.88), BMI (AOR per kg/m²: 1.21; 95% CI: 1.10–1.33), diabetes duration (AOR per year: 1.07; 95% CI: 1.00–1.15) and HbA1c (AOR per 1% increase: 1.44; 95% CI: 1.12–1.85) remained independently associated with thyroid dysfunction. Conclusion: Thyroid dysfunction affected approximately one-fifth of patients with T2DM, with subclinical hypothyroidism being the most common pattern. Targeted thyroid-function assessment may be beneficial, particularly among women and patients with obesity, longer diabetes duration or poor glycaemic control.

Keywords: body mass index; glycaemic control; hypothyroidism; prevalence; thyroid dysfunction; type 2 diabetes mellitus.