Modulation of Pituitary LH and Prolactin Pools in Amenorrheic Women I. Effects of High Dose Estrogen or Gestagen Treatment
22 April 2008 (online)
The pituitary LH and PRL pools were investigated in normally cycling volunteers as well as in amenorrheic women using repeated LH-RH and metoclopramide (MTCL) stimulation, respectively. Following each injection of LH-RH significant increases of LH were observed in the volunteers. During the early follicular and midluteal phase of the menstrual cycle the greatest response was noted after the third LH-RH bolus, while during the late follicular phase, the LH release to the first stimulation was greatest. In patients with functional normoprolactinemic amenorrhea LH release patterns were similar to those observed during the early follicular phase of the menstrual cycle except that after the third bolus injection of LH-RH no significant amounts of LH were released. Retesting of the patients, after either a gestagen or estrogen withdrawal bleeding test had been carried out, revealed that the LH release was profoundly diminished after each LH-RH bolus.
Estimating pituitary PRL release capacity by MTCL stimulation a continuous augmentation was observed from the follicular to the luteal phase of the menstrual cycle. Following gestagen as well as estrogen withdrawal bleeding tests amenorrheic patients exhibited an increased PRL release to MTCL stimulation, which was more pronounced after estrogen than gestagen application.
The data presented suggest that the negative feedback in amenorrheic patients is functioning and gestagens as well as estrogens decrease not only the readily releasable pituitary LH pool but also the total LH capacity. This observation casts doubt on the therapeutic usefulness of gestagen as well as estrogen withdrawal bleeding tests in individuals, where induction of ovulation by means of antiestrogens is indicated. In contrast, high doses of both sex steroids, synthetic gestagens as well as estrogens increase pituitary PRL reserve in amenorrheic women.
Pituitary LH - PRL - Estrogens - Gestagens