Investigation of the relationship between serum ISTHMIN-1 levels and insulin resistance along with other metabolic and hormonal parameters in patients with prolactinoma

ABSTRACT INVESTIGATION OF THE RELATIONSHIP BETWEEN SERUM ISTHMIN-1 LEVELS AND INSULIN RESISTANCE ALONG WITH OTHER METABOLIC AND HORMONAL PARAMETERS IN PATIENTS WITH PROLACTINOMA Hyperprolactinemia is a common endocrine disorder characterized by elevated prolactin levels beyond physiological limits. The most frequent cause is prolactinoma, a benign pituitary adenoma. Increased prolactin levels have been shown to affect glucose metabolism and insulin sensitivity. Isthmin-1 (ISM1), a novel adipokine secreted from adipose tissue, has recently attracted attention as a potential metabolic biomarker due to its association with glucose homeostasis and lipid metabolism. The aim of this study was to investigate serum ISM1 levels in patients with prolactinoma and to evaluate their relationship with selected metabolic and hormonal parameters. The study included 30 patients aged 18–65 years diagnosed with prolactinoma who presented to the Endocrinology and Metabolism Diseases Clinic of Fırat University Faculty of Medicine, along with 30 age- and sex-matched healthy controls without systemic disease. Fasting blood samples were obtained from all participants to measure serum ISM1 levels, fasting glucose, insulin, lipid profile, and selected hormonal parameters. Serum ISM1 levels were significantly higher in the prolactinoma group compared to the control group (p<0.01). In addition, a positive correlation was observed between serum ISM1 levels and serum insulin concentrations. These findings suggest that ISM1 may play a role in insulin metabolism and overall energy homeostasis in patients with prolactinoma. Further large-scale, prospective studies are needed to clarify the clinical utility of ISM1 as a metabolic biomarker and to better understand its pathophysiological effects. Keywords: Prolactinoma, Isthmin-1, Adipokine, Metabolic Parameters, Hyperprolactinemia