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Participation of Endogenous Opiates in Regulation of the Hypothalamic-Pituitary-Testicular Axis in Normal Men^*

Chair of Endocrinology, University of Sassari Sassari, Italy
The Chair of Endocrinology, University of Genoa Genoa, Italy

Address of correspondence and requests for reprints to: Dr. Giuseppe Delitala, Chair of Endocrinology, Istituto di Patologia Medica 1, Viale San Pietro n. 12, 07100 Sassari, Italy.

To assess the influence of endogenous opioids on human gonadotropin secretion, integrated concentrations of gonadotropins during 24-h naloxone infusion (2.08 mg/h) were examined in a group of six normal men. Naloxone significantly stimulated LH secretion in all subjects, whereas serum FSH levels were similar during both saline and naloxone infusion. Serum testosterone, dihydrotestosterone, and 17-hydroxyprogesterone levels increased during the infusion of naloxone, but the ⁴-androstenedione concentration was not modified. The frequency and amplitude of LH secretory episodes were clearly increased when an equal amount of the drug was given and LH concentrations were measured every 15 min for 6 h. The results suggest the endogenous opioids inhibit the hypothalamic-pituitary-gonadal axis in normal men.

^* This work was supported by CNR Grant 81.00188.04 and a grant from the Ministero della Pubblica Istruzione (to G.D.).

Received July 8, 1982.