[Pulsatile secretion of prolactin during the human menstrual cycle]

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 the menstrual cycle. Blood samples were obtained at 10-min intervals beginning at 1000 h for a duration of 4-7 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 and 74 LH pulses were detected and about 80% of these PRL pulses were observed to coincide with LH pulses. The mean (+/- SD) pulse frequency 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 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 of PRL did not alter. Further, a positive linear correlation between the pulse frequency of PRL and LH (r = 0.74; p less than 0.001) was found throughout the three phases of the cycle.(ABSTRACT TRUNCATED AT 250 WORDS)