Insulin Resistance in Nodular Thyroid Disease

Background. Insulin had been shown to have a mitogenic effect on thyroid cell cultures. The aim of this study was to investigate insulin resistance in patients with euthyroid nodular goiter. Methods. Sixty-three patients with nodular thyroid disease and 83 healthy controls were included in the study. Both the patient and the control group were euthyroid, euglycemic and normotensive. None of the study subjects had risk factors for insulin resistance. All the study subjects were evaluated by serum insulin levels and biochemical parameters and thyroid ultrasound. All subjects with thyroid nodules greater than 1cm (n == 36) were offered to undergo thyroid fine needle aspiration biopsy. Results. The two groups were similar with respect to age, gender, BMI, waist circumference, serum lipid levels, serum fT3, fT4 and TSH levels. But HOMA was found to be significantly higher in the patient group (p: 0.007) and thyroid volume was significantly greater in the patient group (p == 0.03). In the patient group there was a significant correlation between HOMA and nodule volume (p < 0.001) while there was not a significant correlation between HOMA and number of thyroid nodules. Thyroid cancer was diagnosed in 3 of the 36 patients (8.33 %%). Conclusions. Insulin resistance may induce increased thyroid proliferation and nodule volume and nodule formation. Therefore, insulin resistance may be a risk factor for euthyoid nodular goiter.