Observational Study Evaluating Association of Type 2 Diabetes Mellitus and Thyroid Dysfunction

Abstract

BACKGROUND Type 2 diabetes mellitus (T2DM) appears to influence thyroid function by various mechanisms. The exact association between T2DM and thyroid dysfunction has not been documented from Kerala; hence this study is conducted to determine the prevalence of thyroid dysfunction among T2DM patients and to determine the association between T2DM and thyroid dysfunction. MATERIALS AND METHODS Our prospective observational study enrolled 150 T2DM patients diagnosed using ADA diagnostic criteria. Institutional Ethics Committee approved the study and written informed consent was obtained from all study participants. Data was collected in case record forms, which included history, examination findings and laboratory investigations assessing glycaemic control and thyroid function. Values are expressed as mean (standard deviation). Analysis was done using R® and tests of significance used were independent sample 't' test, ANOVA and Chi square test. p <0.05 was considered statistically significant. RESULTS Mean age, duration of T2DM and glycated haemoglobin (HbA1c) of the study participants were 60.1 (7.9) years, 13 (5.9) years and 7.7 (0.8)% respectively 56.7% participants were having higher than normal Body Mass Index (BMI). 80% of participants were females and thyroid dysfunction was seen in 16.7% participants. Among the study participants, 13.3% (n=20) had overt hypothyroidism, 2% (n=3) had subclinical hypothyroidism and 1.3% (n=2) had overt hyperthyroidism. Significant difference in weight (p=0.01), BMI (p<0.001) and HbA1c (p=0.006) was observed when participants were categorized based on thyroid swelling. Significant difference in BMI (p<0.001) and fasting plasma glucose (p<0.001) was observed when participants were categorized based on type of thyroid dysfunction. Significant difference in thyroid stimulating hormone (p<0.001) and HbA1c (p=0.02) was observed when participants were categorized according to BMI. Association was observed between ADA glycaemic goal and type of thyroid dysfunction (p<0.001). CONCLUSION 16.7% of the T2DM patients had thyroid dysfunction, hypothyroidism was the predominant dysfunction. Failure to recognize the presence of thyroid dysfunction among T2DM patients may be a primary reason for poor management of diabetes. We recommend screening for thyroid dysfunction and regular monitoring of thyroid function in T2DM patients.