Concomitant pulsatile release of prolactin and luteinizing hormone in hypogonadal women

The finding that exogenous LRF administration induces PRL release prompted us to examine the possibility that spontaneous pulses of PRL and LH may occur concomitantly in women. Blood samples were obtained between 0800 and 1600 h at 15-min intervals for a duration of 6-10 h in 10 hypogonadal women. Distinct pulsatile fluctuations of plasma PRL concentration were present in all subjects and 96% of these pulses were observed to coincide with LH pulses. The mean (+/- SE) increment of PRL (nadir to peak) was 4.3 +/- 0.3 ng/ml (61.7 +/- 5.1%). The mean interval between pulses of LH was 87.6 +/- 3.6 min and between pulses of PRL was 110.4 +/- 10.4 min. The time course for the ascending and descending limbs of PRL pulses were similar to those of LH pulses, and qualitatively resembled those induced by pulses of exogenous LRF. The finding of a synchrony between the endogenous pulses of LH and PRL during the waking hours of the day in the hypogonadal woman suggests that pulsatile release of PRL and LH may be mediated through a common neuroendocrine mechanism.