Modulation of Pituitary LH and Prolactin Pools in Amenorrheic Women I. Effects of High Dose Estrogen or Gestagen Treatment

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Abstract
The pituitary LH [luteinizing hormone, lutropin] and PRL [prolactin] pools were investigated in normally cycling volunteers as well as in amenorrheic women using repeated LH-RH [luteinizing hormone-releasing hormone, luliberin] and metoclopramide (MTCL) stimulation, respectively. Following each LH-RH injection, 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 3rd LH-RH bolus, while during the late follicular phase, the LH release to the 1st 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 3rd bolus injection of LH-RH no significant amounts of LH were released. Retesting of the patients, after either a gestagen or estrogen [medroxyprogesterone acetate or ethinylestradiol] withdrawal bleeding test was carried out, revealed that the LH release was profoundly diminished after each LH-RH bolus. Estimating pituitary PRL release capacity by MTCL stimulation a continous 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. Evidently 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 ovulation induction by means of antiestrogens is indicated. High doses of both sex steroids, synthetic gestagens as well as estrogens increase pituitary PRL reserve in amenorrheic women.