Euthyroid Nodular Disease in Relation to Insulin Resistance

Background: Nodular thyroid disease is a common endocrine problem. There is scarce information on the effect of hyperinsulinemia on the development of thyroid nodules. Objectives: to assess the frequency of insulin resistance (IR) in patients with euthyroid nodular thyroid disease, and to investigate any possible association between insulin resistance and thyroid functional and/or morphological changes within a sample of Egyptian patients. Research design and methods: This is a cross-sectional study including sixty subjects having euthyroid nodular thyroid disease, their ages ranged from 25 to 60 years old. They were purposively selected and evaluated for manifestations of IR. For all subjects, waist circumference (WC) and body mass index (BMI) were measured. Serum TSH, FreeT4, FreeT3, fasting plasma glucose, and fasting serum insulin (FI) were measured. Degree of IR was calculated using Homeostasis model Assessment-index (HOMA-index). Thyroid ultrasound (US) was performed and thyroid volume (TVml), nodule volume (NVmm), and nodular number (NN) were measured. Results: According to results of HOMA-Index, 56.70% of studied subjects had levels >2.7 denoting significant IR. No significant difference was found between subjects with and those without IR as regards thyroid profile. Subjects with IR had more frequent thyroid nodules besides greater TV and NV. Among the studied parameters, multivariate linear regression analysis revealed that, TV was mainly associated with FI and HOMA-index (p<0.000, p<0.002, respectively). The main predictors for developing more than one nodule were BMI, TV, HOMA-index, and FI. None of the studied parameters had an association with NV. Conclusions: IR is common among Egyptian patients with euthyroid nodular thyroid disease. Thyroid gland is a novel vulnerable tissue that may be affected by IR, in the form of increased thyroid volume and higher risk of nodule formation.