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

Abstract

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