Activation of pituitary gonadotropic function by an agonist of luteinizing hormone-releasing factor in the puerperium.

To test the hypothesis that long-term deprivation of endogenous luteinizing hormone-releasing factor (LRF) during the course of pregnancy may account for the lack of gonadotropin in the puerperium, six normal postpartum women were treated with the potent and long-acting LRF agonist (D-Trp6, Pro9-NEt)-LRF. A 50 microgram dose of LRF agonist was administered subcutaneously every 48 hours for four doses, with the first dose given on the first day post partum. Prior to treatment, each subject was tested with two pulses of LRF (10 micrograms at 2 hour intervals) and again at the end of LRF agonist treatment on day 10 post partum. Pulses of LRF induced no significant elevation of follicle-stimulating hormone (FSH) levels on day 1 post partum. During treatment, a significant (P less than 0.005) increase in basal FSH levels occurred after the second dose of LRF agonist administration. Following treatment, pulses of LRF elicited a remarkable gonadotropin release with a relatively greater percent rise for FSH than for human chorionic gonadotropin-luteinizing hormone. Our data indicate that the lack of gonadotropin activity during the first 3 weeks post partum is, at least in part, related to insufficiency of endogenous LRF secretion and that resumption of gonadotropin secretion can be functionally activated by treatment with the appropriate dose and intervals of an LRF agonist.