Disparate effects of naloxone in hypothalamic amenorrhoea of athletes

Of 30 amenorrhoeic women athletes, 28 were considered to have hypothalamic amenorrhoea according to their low gonadotropin, estradiol (E2) and normal testosterone and prolactin (PRL) values. Gonadotropin-releasing hormone (LH-RH 100 micrograms i.v.) and naloxone (4 mg i.v. bolus followed by 2.8 mg/h infusion) tests were administered consecutively. Fifteen subjects reacted to the naloxone test with at least a fivefold increase in LH values; these values were consistently above those of the LH-RH test. The other 13 women reacted similarly to the releasing hormone but not to naloxone. While there were no differences between basal LH values in the two groups, E2 levels tended to be lower in non-responders, but since 1/3 of the values fell below the threshold of sensitivity of the E2 assay, no significance could be calculated. The obvious difference among the subjects could be E2 -mediated, the non-responders representing a deeper level of hypothalamic amenorrhoea. The naloxone test seems to be useful for differentiating between different forms of this condition.