Subclinical hyperthyroidism in patients with type 2 diabetes

Both subclinical hyperthyroidism and type 2 diabetes (T2D) have been associated with an increase in cardiovascular disease risk and mortality. We aimed to assess the prevalence of newly diagnosed subclinical hyperthyroidism in a cohort of patients with T2D, and also to analyse the relationships between diabetes-related characteristics and the presence of subclinical hyperthyroidism. 933 diabetic patients without previous history of thyroid disease (45.4% females, mean age 66.3 years, median duration of diabetes 10 years) were evaluated. A sample of 911 non-diabetic subjects without known thyroid dysfunction was studied as control group. Serum concentrations of thyrotropin were measured in all subjects. Subclinical hyperthyroidism was present in 4.3% of female and 3.5% of male diabetic patients. Relative risk was significant only for the female gender (OR 3.69, 95% CI 1.56-8.71). In comparison with diabetic patients without thyroid hyperfunction, patients with subclinical hyperthyroidism were older, had longer duration of diabetes, showed lower fasting glucose levels, had greater proportion of goitre and diet therapy, and had lower proportion of treatment with oral agents. Logistic regression analysis showed that age and the presence of goitre were significantly related to subclinical hyperthyroidism in patients with T2D. The risk for subclinical hyperthyroidism is increased in women with T2D. Advanced age and the presence of goitre are significantly and independently related with the presence of subclinical hyperthyroidism in diabetic population.