Circulating Levels of Orexin-A, Nesfatin-1, Agouti-Related Peptide, and Neuropeptide Y in Patients with Hyperthyroidism

Background: There is insufficient information about the appetite-related hormones orexin-A, nesfatin-1, agouti-related peptide (AgRP), and neuropeptide Y (NPY) in hyperthyroidism. The aim of the present study was to investigate the effects of hyperthyroidism on the basal metabolic rate (BMR) and energy intake, orexin-A, nesfatin-1, AgRP, NPY, and leptin levels in the circulation, and their relationship with each other and on appetite. Methods: In this prospective study, patients were evaluated in hyperthyroid and euthyroid states in comparison with healthy subjects. Twenty-one patients with overt hyperthyroidism and 33 healthy controls were included in the study. Results: Daily energy intake in the hyperthyroid state was found to be higher than that in the euthyroid state patient group ( p =0.039). BMR was higher in hyperthyroid patients than the control group ( p =0.018). Orexin-A was lower and nesfatin-1 was higher in hyperthyroid patients compared to the controls ( p <0.001), whereas orexin-A increased and nesfatin-1 decreased after euthyroidism ( p =0.003, p <0.001). No differences were found in the AgRP, NPY, and leptin levels between the hyperthyroid and euthyroid states and controls ( p >0.05). Orexin-A correlated negatively with nesfatin-1 ( p =0.042), BMR ( p =0.013), free triiodothyronine (fT3; p <0.001), and free thyroxine (fT4; p <0.001) and positively with thyrotropin (TSH; p <0.001). Nesfatin-1 correlated negatively with orexin-A ( p =0.042) and TSH ( p <0.001) and positively with fT3 ( p =0.005) and fT4 ( p =0.001). In the regression analysis, “diagnosis of hyperthyroidism” was the main factor affecting orexin-A ( p <0.001). Conclusions: Although it seems that no relationship exists among orexin-A, nesfatin-1, and increased appetite in hyperthyroidism, the orexin-A and nesfatin-1 levels are markedly affected by hyperthyroidism.