Naloxone administration does not affect gonadotrophin secretion in male patients with isolated hypogonadotrophic...

We evaluated the gonadotrophin response to acute naloxone administration (10 mg iv) in 4 male patients with isolated hypogonadotrophic hypogonadism (age range 18.5-26 years) before and after pituitary priming with daily infusions of GnRH (25 micrograms/h for 4 h) for 4 days. A blunted gonadotrophin response to acute GnRH administration (100 micrograms iv) and a lack of response to naloxone was observed before pituitary priming. After repeated infusions of GnRH, pituitary gonadotrophin responsiveness to GnRH was restored, whilst naloxone still did not affect gonadotrophin levels. Our data suggest that in male isolated hypogonadotrophic hypogonadism 1) the lack of pituitary response to naloxone is not due to pituitary hyporesponsiveness to GnRH; 2) endogenous opioids do not exert any inhibitory influence on GnRH secreting neurons and thus are not involved in the pathogenesis of this disease.