ACTA ENDOCRINOLOGICA (BUC)

Context. Irisin, a cleaved product of fibronectin type III domain-containing protein 5 (FNDC5), has been proposed as a key molecular link between energy metabolism and reproductive regulation. Emerging evidence suggests that it modulates hypothalamic-pituitary-gonadal (HPG) activity and oxidative balance, but its reproductive effects in males remain insufficiently defined. Objective. To evaluate the endocrine, antioxidant, and reproductive responses to exogenous irisin administration in healthy male Wistar rats. Design. A controlled, time-course experimental study was conducted to assess hormonal, biochemical, and sperm-related outcomes following irisin treatment. Subjects and Methods. Twenty-four adult male Wistar rats were randomly allocated to Control (saline) or Treated (irisin, 200 ng/kg, subcutaneous) groups, with sample collection on days 10, 20, and 30. Serum levels of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, lipid profiles, and oxidative stress biomarkers [malondialdehyde (MDA), reactive oxygen species (ROS), total antioxidant capacity (TAC)] were analyzed. Sperm count, motility, and morphology were also evaluated. Results. Irisin administration significantly increased serum GnRH, LH, FSH, and testosterone concentrations (p < 0.001), indicating activation of the HPG axis. Lipid parameters remained unchanged. Oxidative stress markers were favorably modulated, with reduced MDA and ROS (p < 0.05) and a progressive increase in TAC over time (p < 0.05, group × day interaction). Sperm count was higher in the Treated group (p < 0.05), while motility and morphology were not significantly affected. Conclusions. Subcutaneous irisin administration enhances reproductive hormone secretion, improves antioxidant capacity, and increases sperm production in male rats without altering lipid metabolism. These findings suggest that irisin may serve as a potential therapeutic modulator of male reproductive function, particularly under conditions involving oxidative stress or endocrine disruption.