Abstract： Objective This study aims to investigate the prevalence and associated risk factors of thyroid dysfunction among patients receiving nivolumab treatment in real world settings.Methods Retrospective collection of clinical data from patients administered nivolumab at the First Affiliated Hospital of Nanchang University between October 2019 and March 2023 was conducted.Results The incidence of thyroid dysfunction stood at 23.8%,with hypothyroidism emerging as the most prevalent manifestation.Hypothyroidism typically manifested at 12 weeks,whereas hyperthyroidism surfaced at 6 weeks post-treatment initiation.Patients with a BMI below 18.5 kg/m2 had a higher incidence of thyroid dysfunction(P=0.029).Conclusion Individuals with a BMI below 18.5 kg/m2 are more susceptible to developing thyroid dysfunction while undergoing nivolumab therapy.Vigilance regarding alterations in thyroid function is crucial when patients undergoing nivolumab treatment experience rapid weight fluctuations.