Pulsatile secretion of prolactin during the human menstrual cycle
Masaoka, K.; Kitazawa, M.; Niibe, T.; Kumasaka, T.
Nihon Sanka Fujinka Gakkai Zasshi 40(12): 1793-1799
1988
ISSN/ISBN: 0300-9165 PMID: 3209907 Document Number: 309404
Recent investigations have demonstrated the pulsatile nature of prolactin (PRL) secretion and the synchronous relationship between PRL and LH pulses in normal and hypogonadal women. The present study was designed to confirm this synchrony and to investigate the characteristics of PRL pulses at different stages of menstrual cycle. Blood samples were obtained at 10-min intervals beginning at 1000 h for a duration for 4 .apprx. 7 h in women during the follicular (n=11), preovulatory LH surge (n=2) and luteal phases (n=10). Detectable pulses in plasma PRL concentrations were present in almost all subjects during the each phase of the cycle. During the total 121 h-blood sampling throughout the three phases, 62 PRL pulses 74 LH pulses were detected and about 80% of these PRL pulses were observed to coincide with LH pulses. The mean (.+-.SD) pulse frequently of PRL was significantly lower during the luteal phase (0.28 .+-. 0.17 pulses/h) than during the follicular (0.64 .+-. 0.25 pulses/h) and preovulatory phases (0.72 .+-. 0.16 pulses/h). The mean pulse amplitude of of PRL was significantly greater during the luteal phase (6.8 .+-. 2.3 ng/ml) than during the follicular (3.6 .+-. 1.2 ng/ml) and preovulatory phases (4.8 .+-. 1.4 ng/ml). These changes in pulse frequency and amplitude were also observed in LH pulses between the follicular and luteal phases, except during the LH surge when LH pulse amplitude increased markedly, whereas that the PRL did not alter. Further, a positive linear correlation between the pulse frequency of PRL and LH (r=0.74; p < 0.001) was found throughout the three phases of the cycle. These results demonstrate that a marked degree of synchrony between PRL and LH pulses is observed during the menstrual cycle and suggest that the frequency and amplitude of PRL pulses vary from the follicular to luteal phases, except during the LH surge, almost in parallel with those of LH pulses.