Triptorelin is a gonadotropin-releasing hormone agonist that is a potent inhibitor of testosterone (in men) and estrogen (in women) synthesis and is used to treat advanced prostate cancer. Studies of the mechanisms of regulation and synthesis of testosterone formation in testicular interstitial cells demonstrate multiple endogenous targets that can increase testosterone biosynthesis, which may moderate the effects of testosterone depletion. Triptorelin, a synthetic analog of the neurohormone gonadoliberin, suppresses the expression of the GnRH receptor in the pituitary gland, but does not change the functioning of the pituitary-testicular complex. The purpose of the work is to study the electron microscopic changes in the interstitial endocrinocytes of the testes of rats after the administration of triptorelin for 365 days. The experiment was conducted on 35 sexually mature male white rats. The rats were divided into 2 groups: the control group (I) was injected with a physiological solution, the II group with central deprivation of the synthesis of luteinizing hormone was injected subcutaneously with triptorelin at a dose of 0.3 mg of the active substance per kg of the rat's body weight. The study of the interstitial space in the testicles of white rats showed that long-term administration of triptorelin causes hormonal dysregulation of the hypothalamus-pituitary-testis system, which leads to quantitative and qualitative changes in the endocrine cells of the interstitial space of the testis, which is confirmed by electron microscopic changes in subcellular structures. The maximum effect of triptorelin is determined from the 180th day of observation, which is characterized by an increase in degenerative changes in endocrinocytes, and the detection of Reinke crystals in the cytoplasm of interstitial endocrinocytes from the 270th day of observation.