Background: Neudesin is a peptide secreted in brain and adipose tissues that has neural and metabolic functions. Its role as regulator of energy expenditure leads to assumption that its level may be regulated depending on thyroid gland pathology. Objective: This study aimed to investigate serum neudesin levels in patients with thyroidism and to evaluate₁ any possible relationship between plasma neudesin levels and thyroid hormone levels. Methods: The study included 100 women with newly diagnosed thyroidisim were subdivided into two groups: hyperthyroidism group (50 female patients with₁ age ranged from 18 to 60 years) and hypothyroidism group (50 female patients with age ranged from 18 to 75 years). A control group (30 healthy females with age ranged from 18 to 70 years) was also included for comparison. Body mass index (BMI) was evaluated. Plasma glucose, lipid profile, triiodothyronine (T3), thyroxin (T4), free T3, free T4, thyroid stimulating hormone (TSH), and neudesin levels were evaluated in all participants using ELISA kit. Results:The hyperthyroidism group had significantly (p=0.001) higher serum neudesin concentrations (4.47 ± 2.28 ng/mL) than in hypothyroidism (1.15 ± 0.43 ng/mL) and control groups (1.06 ± 0.36 ng/mL). A correlation analysis₁ applied to the whole study group revealed a positive correlation between serum neudesin concentration and T4 in patients with hypothyroidism. Conclusions: Due to the relation of increased₁ levels of neudesin in hyperthyroidism, neudesin may₁ be related with one of pathophysiologic pathways of thyroidism. Still, it is not certain that higher neudesin level is involved in the pathogenesis₁ of thyroidism or as a result of the disorder.