Alterations of Serum Leptin Levels in Patients with Autoimmune Thyroid Disorders

Background: Thyroid dysfunction is accompanied with significant metabolic alterations that affect body weight, appetite, and energy expenditure, as well as lipid and carbohydrate metabolism. Leptin, an adipokine produced by adipocytes, regulates food intake and energy storage. Thyroid hormones and leptin share some physiological effects. Changes in leptin have been shown in patients with dysfunction of the thyroid; however, the results are contradictory. The aim of this study was to evaluate the circulating levels of leptin in patients with Graves disease (GD) and Hashimoto thyroiditis (HT) before and after normalization of thyroid function compared with the control group. Methods: Newly diagnosed adult patients with GD, HT, and healthy euthyroid controls were recruited. Various clinical and biochemical parameters, including thyroid function tests and serum leptin level, were assessed before and after treatment and compared between groups. Results: Data from 56 patients with HT, 54 patients with GD, and 54 healthy controls were analyzed. Serum leptin levels of patients with HT (30.96 ± 3.88 ng/mL) were found to be significantly higher than the controls (22.35 ± 4.72 ng/mL) (p<0.001), whereas patients with Graves had lower serum leptin levels (14 ± 4.54 ng/mL) (p<0.001). In patients with HT, serum leptin levels showed a significant decrease after treatment (31 vs 27 ng/mL; p<0.001), while in patients with GD, leptin increased significantly after treatment (14 vs 17 ng/mL; p<0.001). Conclusion The present study showed that serum leptin levels increased in patients with HT and decreased in those with GD than the control group. However, after treatment, leptin decreased in the Hashimoto group and increased in the Graves group, although it was still significantly different from the control group.