Prevalence of and Factors Associated with Hypothyroidism in Patients with Type 2 Diabetes Mellitus in Basrah

Objective: This retrospective study aimed to determine the prevalence of hypothyroidism in patients with type 2 diabetes (T2D) and analyze factors associated with its diagnosis, as well as its association with T2D-related complications. Material and methods: Data were collected from 5145 patients with T2D attending two specialized centers in Basrah, Iraq, from 2009 to 2024. Thyroid function tests were performed using chemiluminescence immunoassay, with hypothyroidism defined as elevated thyroid-stimulating hormone (TSH) and low free thyroxine (fT4) or subclinical hypothyroidism (elevated TSH with normal fT4). Clinical and biochemical data, including age, gender, body mass index (BMI), T2D duration, glycemic control, lipid profile, and diabetes-related complications, were analyzed. A multinominal regression analysis was performed to assess the factors linked to hypothyroidism, and to study the effect of hypothyroidism and other factors on T2D-related complications. Results: The prevalence of hypothyroidism in T2D patients was 16.8%, with no significant temporal variation. We found that HbA1c more than 7% (53 mmol/mol) and insulin-treated patients were associated with decreased risk of hypothyroidism, while female gender, BMI of 30 kg/m 2 and higher, T2D duration of 10 years or longer, hypertension, and uncontrolled dyslipidemia were associated increased risk of hypothyroidism. The presence of hypothyroidism was independently associated with excess diabetic neuropathy, retinopathy, nephropathy, and cardiovascular disease. Conclusion: Hypothyroidism is highly prevalent in T2D patients and is associated with increased risk of diabetes-related complications. This finding highlights the need for routine thyroid screening in this population.