Nalmefene enhances LH secretion in a proportion of oligo-amenorrheic athletes.

The influence upon LH secretion of doses of nalmefene, an orally effective congener of naloxone, and a placebo was compared in nine oligo-amenorrheic athletes with that in five regularly menstruating non-athletic women as a test for periodic elevations in hypothalamic opioid tone. After a 360-min control period, LH levels were followed for an additional 360 min following ingestion of the medications in random order approximately six weeks apart, 10-min blood sampling being employed throughout. The mean amplitude post-nalmefene in the athletes was significantly greater than pre (p < 0.05), although there were no differences in the frequency of LH pulses after placebo or nalmefene ingestion. Subjects were labelled as "responders" if their peak AUC after treatment exceeded their pretreatment AUC for LH by more than 1.96 SD (p < 0.05). There were no placebo responders, but 5/9 of the athletes and 1/5 of the menstruating controls were classified as nalmefene responders (p < 0.05). In addition, a variable proportion of the athletes (but none of the controls) experienced symptoms suggestive of narcotic withdrawal 1-4 h after ingesting nalmefene and again 12-18 h later. It appears that demonstrable increases in opioid tone occur at least transiently in a proportion of oligo-amenorrheic athletes.