Effects of exogenous estrogen and progestin on pituitary responsiveness to synthetic luteinizing hormone-releasing factor.

The effect of estrogen and progestin on pituitary responsiveness to 150 mug synthetic luteinizing hormone-releasing factor (LRF) was assessed in premenopausal women receiving sequential (n=12) and combination (n=7) contraceptive steroids. A marked contrast in the time-course and maximal response to LRF was found; a prompt but quantitatively smaller luteinizing hormone (LH) response was seen during cyclic combination therapy, while a delayed (five times) but enhanced (fivefold) LH response was observed during estrogen segments of cyclic sequential therapy. For follicle-stimulating hormone (FSH), the maximum rise was also higher, and the peak response was similarly delayed in the latter group. The quantitative secretion in response to LRF for LH (area under the curve), but not for FSH, was significantly greater (P < 0.01) in subjects receiving sequential, as compared to subjects receiving combination treatment. In both groups, characteristic gonadotropin responses to LRF were reproducible and were independent of the duration of treatment. Since LRF studies were performed during the estrogen segment of treatment cycle in subjects receiving sequential steroids, our data suggest that estrogen exerts a direct feedback action at the pituitary level and that pituitary responsiveness to LRF is augmented by estrogen.

Bone mineral: effects of oral contraceptives, pregnancy, and lactation.

Estimating bone mineral by the photon absorption (125I) method applied to the distal part of the radius, it was found that young women using oral contraceptives containing a daily dose of 100 micrograms of mestranol had higher concentrations of bone mineral than non-users. Women twenty to fifty-nine years old who had lactated were among the poorly mineralized, while those who had lactated but were now using oral contraceptives in various combinations were among the highly mineralized.

The effects of some progestational steroids on pubertal ovulation in the rat.

PIP: 15 progestational steroids were tested for their ability to suppress pubertal ovulation in the rat. All of the compounds tested except ethynodiol diacetate inhibited initial ovulation. The steroids tested could be divided into 2 groups based upon their effects on uterine weight. Pregnanes and dimethisterone decreased uterine weight. Nortestosterone derivitives increased the weight of the uterus.^ieng