Mechanism of action of narcotics in the production of menstrual dysfunction in women

The ability of morphine to block ovulation in animals prompted investigation of the frequency and mechanisms of menstrual abnormalities in women addicted to narcotic analgesics. Menstrual histories obtained from 76 former heroin addicts receiving daily methadone maintenance revealed that more than one-half of these women had experienced menstrual abnormalities while taking heroin or methadone. In order to determine the specific physiologic effects of narcotic analgesics on reproductive function, detailed endocrinologic studies were carried out in seven of these patients who complained of amenorrhea or irregular menses while receiving methadone. Four of the seven women manifested abnormalities of the control of gonadotropin secretion. Three of these four failed to exhibit cyclic gonadotropin release, as evidenced by an absence of increased levels of follicular phase follicle-stimulating hormone, midcycle gonadotropin peaks or luteal phase progesterone increments. In the fourth patient a prolonged follicular phase (30 days) of the menstrual cycle was detected. One of these four patients also had low basal gonadotropin levels and failed to exhibit luteinizing hormone increments greater than control levels in response to ethinyl estradiol (positive feedback). The remaining three women exhibited normal patterns of gonadotropin secretion during the observation period. In these women, menstrual bleeding occurred in response to withdrawal from luteal phase (10 to 20 ng/ml) progesterone levels and to exogenous ethinyl estradiol, suggesting normal uterine responsivity to progesterone and estrogen. Although not documented, it is likely that oligo-ovulation was the cause of the irregular menses in these three patients. Amenorrhea is commonly associated with methadone ingestion or heroin addiction and appears to be related to an alteration of the hypothalamic mechanisms controlling gonadotropin secretion. Tolerance to these effects of methadone may develop after chronic ingestion.