The association of autoimmune thyroiditis and non-functional adrenal incidentalomas with insulin resistance

Patients with incidental nonfunctioning adrenal adenoma are associated with increased risk of obesity, impaired glucose tolerance and dyslipidemia. We aimed to investigate the relationship between thyroid function, serum lipids and insulin resistance in patients with nonfunctioning adrenal incidentaloma.

Forty patients who had diagnosed as adrenal incidentaloma (AI) in our department were included in the study. Serum free triiodothyronine (fT3), free thyroxine (fT4), thyroid stimulating hormone (TSH), anti-thyroperoxidase antibody (anti-TPO Ab) and anti-thyroglobulin antibody (anti-Tg Ab), lipid profile, hs-CRP, fasting insulin levels were measured and insulin resistance calculated by HOMA-IR. Thyroid volume (TV) was assessed.

None of the patients showed specific signs and symptoms of hormone excess. TV, TSH and fT3 levels in the patient and control groups did not differ significantly (p > 0.05). The serum fT4, anti-TG Ab, anti-TPO Ab levels in the patient group were significantly higher than in the control group (p = 0.013, p < 0.0001, p = 0.016 respectively). The HOMA-IR, hs-CRP and HDL cholesterol levels in the AI patients were significantly higher than the control group (p = 0.034, p = 0.041, p = 0.002, respectively). Statistically significant relationship was found between HOMA-IR and thyroid volume (r = 0.373, p = 0.018), fT4 (r = 0.382, p = 0.015), hs-CRP (r = 0.512, p = 0.001), HDL cholesterol (r = 0,351 p = 0.026) in AI patients. There were significant correlation between anti-TG Ab, anti-TPO Ab and TSH levels in AI patients (r = 0.431 p = 0.006, r = 0.402 p = 0.012).

Patients with nonfunctioning adrenal incidentaloma have several metabolic disturbances. At the same time autoimmune thyroid disorders are more frequent in nonfunctioning adrenal incidentaloma patient so that thyroid functions must be evaluated in those patients.