Correlation between incremental changes of oestradiol-17 beta and prolactin during the menstrual cycle by means of multiple plasma sampling.

Incremental changes of circulating oestradiol-17 beta (E2) and prolactin (PRL) at midcycle and in the luteal phase were studied in 7 healthy young women by means of multiple plasma sampling over a longer period of time. The mean E2 and PRL levels were significantly higher at both times of assessment than in the follicular phase (p less than 0.001). Rapid fluctuations of both E2 and PRL levels were observed; amplitude of E2 fluctuations was increased at higher mean E2 plasma levels. Regression analysis showed a significant correlation (r = 0.62; p less than 0.01) between the incremental changes of E2 and PRL levels at midcycle and in the luteal phase. The present data shows that changes in the plasma levels of E2, and perhaps in the amplitude of the fluctuations, play a crucial role in the regulation of PRL secretion and release during the normal menstrual cycle.