An analysis of the relative risk for goitre in euthyroid patients with type 2 diabetes

To assess the relative risk for goitre in a cohort of euthyroid patients with type 2 diabetes with special reference to the use of metformin and insulin therapy.

Eight hundred euthyroid patients with type 2 diabetes (433 women, mean age 65·8 ± 12·5 years) and 671 euthyroid subjects without diabetes were retrospectively evaluated. There were 250 patients on metformin and 455 patients on insulin treatment.

The gender-, age-, body mass index- and thyrotropin (TSH)-adjusted relative risk for goitre occurring among diabetic patients relative to controls was 3·01 (1·61-5·64) (P < 0·01). This odds ratio was significant in females, patients with and without metformin therapy, patients without insulin therapy and without micro- and macrovascular complications of diabetes. However, male pateints, patients on insulin therapy or with micro- or macroangiopathy did not exhibit an increase in the risk of goitre. Patients on metformin therapy showed a significant increase in the risk of goitre only in the absence of insulin therapy. Multi-adjusted logistic regression analysis showed that goitre was significantly related to gender, TSH and haemoglobin A1c levels. Metformin and insulin therapy were nonsignificant variables in this model.

This is the first survey analysing the relationship between the presence of palpable goitre and clinical parameters in a large cohort of patients with type 2 diabetes. Our data suggest a significant relationship between goitre and glycaemic control, but do not support the presence of independent and significant relationships between goitre and metformin or insulin treatment in euthyroid patients with type 2 diabetes.