Hypericum perforatum L. has numerous physiological effects and contains ingredients like hyperforin and hypericin. Serotonin, dopamine, and GABA were among the neurotransmitters that it affects. Along with these effects, there are also deficiencies in the mechanism pertaining to the relationship between the hormone leptin and H. perforatum, which inhibits the accumulation of fat tissue. Its effects on food intake and weight gain, as well as the mechanism underlying the interaction between leptin and NPY/AgRP genes in the hypothalamus, are poorly understood. There were five groups in the study. The first group was a control group. The second group was given only 1% DMSO. To the third group, 100 mg/kg extract was administered intraperitoneally. 200 mg/kg extract was administered intraperitoneally to the fourth group, and 300 mg/kg extract was administered to the fifth group. Injections were given every day throughout the 10-day experiment. Blood and tissue samples were collected to investigate changes in testicular histology and brain NPY/AgRP gene expressions. The animals' ; locomotor activities, food consumption, and body weights were also measured throughout the experiment. As a result, in parallel with the dose increase, tissue damage in testicular histology increased, while NPY/AgRP expression decreased. High doses of H. perforatum resulted in decreased testosterone levels but increased serotonin and leptin levels. Depending on the dose, H perforatum stimulated nutritional physiology while having a negative effect on testicular physiology. This work was supported by Çanakkale Onsekiz Mart University The Scientific Research Coordination Unit, Project number: FBA-2023-4438