Thyroid Dysfunction, Associated Factors and Glycaemic Control Among Patients with Diabetes Mellitus in a Tertiary Hospital

Background: Diabetes mellitus and thyroid disorders are among the most common endocrine diseases. Thyroid dysfunction is more prevalent among diabetic patients than in the general population. These two disorders affect each other, making their management dependent on the control of both conditions. This study examined the prevalence of thyroid dysfunction, associated factors and glycaemic control among diabetic patients at Muhimbili National Hospital. Methods: This cross-sectional study among diabetic outpatients was conducted from September to November 2021. Data was collected on sociodemographic, anthropometric and clinical characteristics. All patients underwent thyroid gland neck examination. Blood samples were drawn for random blood glucose (RBG), glycated haemoglobin (HbA1C), thyroid function tests [Triiodothyronine (T3), Tetraiodothyronine (T4) and Thyroid Stimulating Hormone (TSH)]. HbA1C ≥7% was defined as poor glycaemic control, while thyroid hormone levels outside the reference range were considered indicative of thyroid dysfunction. Categorical variables were summarized as proportions, while continuous variables were summarized as means. Chi- square or Fischer’s exact test was used to compare proportions in categorical variables. Logistic regression was used to analyse the predictors for thyroid dysfunction. The Akaike information model was used for analysis of the factors in the multivariate model where a p value of <.05 was considered statistically significant. Results: A total of 403 diabetic patients were studied. Of these, 75.7% were overweight or obese. Thyroid dysfunction was present in 16/403 (3.97%) participants. Of the patients with thyroid dysfunction, 5/16 (31.25%) had hypothyroidism and 11/16 (68.75%) had hyperthyroidism, both being subclinical. Female sex was the only significant predictor of thyroid dysfunction in this study population [AOR 2.9 (1.01-8.3); p=.047]. Overall, 14/16 (87.5%) patients with thyroid dysfunction had a poor glycaemic control. Conclusion: In this study conducted in Tanzania, thyroid dysfunction had a low prevalence among patients with diabetes mellitus, with females being at greater risk. Subclinical hyperthyroidism was more common than hypothyroidism. Poor glycaemic control was observed in approximately three quarters of the studied diabetic patients. Hypertension and overweight or obesity conditions were also common in the population studied. Future studies on thyroid dysfunction in diverse populations, including patients with type I diabetes mellitus, in sub-Saharan Africa are warranted