Díaz S, Seron-Ferre M, Croxatto H B, Veldhuis J
Unidad de Reproducción y Desarrollo, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile.
Biol Res. 1995;28(2):155-63.
The current knowledge on the mechanisms of lactational infertility, discussed during a symposium of investigators in this subject, is reviewed. Three periods of lactation are examined: the first weeks postpartum, the period of extended lactational amenorrhea and the recovery of ovarian function. In the first postpartum weeks the inhibition of ovarian function is accounted by diminished pituitary response to GnRH, since exogenous GnRH fails to elicit a LH increase. Suckling can extend the period of ovarian inhibition for weeks, months or years, although it does not fully suppress pulsatile secretion of LH beyond the first weeks. Extended lactational amenorrhea is associated with low LH plasma levels, a great PRL increase in response to suckling, low basal E2 levels and a suppression of estrogen positive feedback. Decreased immunoreactive LH levels may result from partial suppression of the LH pulse generator and a smaller mass of GnRH released in each burst. The role of neurotransmitters, PRL and ovarian factors is discussed. After the recovery of ovulatory cycles suckling still has a residual infertility effect, associated to inadequate luteal function. The sources of variation among women and populations were recognized. Areas in which research is needed to improve the understanding of the mechanisms that sustain lactational amenorrhea are suggested.
本文回顾了在该领域研究者研讨会上所讨论的关于哺乳期不孕机制的现有知识。研究了哺乳期的三个阶段：产后头几周、哺乳期闭经延长阶段以及卵巢功能的恢复阶段。在产后头几周，卵巢功能受到抑制是由于垂体对促性腺激素释放激素（GnRH）的反应减弱，因为外源性GnRH无法引起促黄体生成素（LH）升高。尽管哺乳在产后头几周后并不会完全抑制LH的脉冲式分泌，但它可以将卵巢抑制期延长数周、数月或数年。哺乳期闭经延长与血浆LH水平低、哺乳后催乳素（PRL）大幅升高、基础雌二醇（E2）水平低以及雌激素正反馈抑制有关。免疫反应性LH水平降低可能是由于LH脉冲发生器部分受抑制以及每次脉冲释放的GnRH量减少所致。文中讨论了神经递质、PRL和卵巢因素的作用。排卵周期恢复后，哺乳仍有残余的不孕作用，这与黄体功能不足有关。文中认识到了女性和人群之间的差异来源。提出了为增进对维持哺乳期闭经机制的理解而需要开展研究的领域。
