Progesterone and LH variations after LH-RH administration in the luteal phase of the menstrual cycle

We have investigated the pituitary and luteal responses to LH-RH and their related changes. 11 normal women were studied during the luteal phase (day +4/+11). Blood samples were collected every 15 min for a basal period of 180 and 120 min after the intravenous administration of 25 micrograms of LH-RH. Progesterone (P) and LH were assayed by radioimmunoassay. Data were analyzed as maximum peak and its percent increase (delta max), integrated secretory area (ISA) and percent increase of ISA (delta A) in respect to basal values for both P and LH. LH-RH elicited a secretory response of both hormones in all cases. ISA of LH was significantly greater after LH-RH administration in respect to basal values (p less than 0.001) and delta max accounted to 475 +/- (SE) 36% of the basal concentration. Luteal responsiveness varied from about 115-130% to more marked increments. ISA of P differed from basal to stimulated conditions (p less than 0.05) and delta max was 166 +/- (SE) 14%. The analysis of temporal relationship between P and LH secretion showed that LH promptly rose after LH-RH, while the enhancement of P plasma levels occurred within 31 +/- 19 min after LH rise. Then P levels reached a plateau, values of which were statistically different from those observed before LH-RH administration. In two cases where luteal function was blunted or absent, in spite of marked increments of LH, P secretion did not occur. These data are consistent with the presence of close relationships between hypothalamic, pituitary and luteal functions and strengthen the contention about the usefulness of LH-RH during luteal phase for the lifespan and maintenance of corpus luteum.