Pituitary responsiveness to synthetic luteinizing hormone-releasing hormone during pregnancy: effect on follicle-stimulating hormone secretion

Disappearance of human chorionic gonadotropin and resumption of ovulation following abortion

The disappearance of human chorionic gonadotropin (hCG) and resumption of pituitary ovarian function was investigated in 13 patients following first- and second-trimester abortions. First-trimester abortion patients (with suction curettage) had a mean time of 37.5 +/- 6.4 days for the clearance of hCG to a level of 2 mlU/ml. Second trimester abortions (with prostaglandin) had a mean time of 27.4 +/- 4.8 days. Patients undergoing second-trimester hysterectomy had a mean disappearance time of 39.7 +/- 5.3 days and only 12 days if the hysterectomy was initiated with ligation of the uterine and ovarian vessels. No significant difference in clearance time was found when it was compared on the basis of the baseline hCG levels. Based on a concomitant luteinizing hormone (LH) and follicle-stimulating hormone (FSH) peak, nine of 12 patients resumed normal pituitary function. These LH and FSH peaks were seen even though the serum hCG levels were as high as 35 mlU/ml. Based on serum progesterone levels of greater than 3 ng/ml, all these nine patients ovulated as early as 21 days after abortion. In view of these results, the clearance of hCG after pregnancy termination depends mainly upon the type of procedure used. Moreover, in view of the early time of ovulatory recovery, contraception should be instituted within the first 2 weeks following pregnancy termination.

Serum follicle stimulating hormone levels in human pregnancy

We describe a specific radioimmunoassay for follicle stimulating hormone (FSH) and the finding of immunoreactive FSH in human pregnancy sera. A total of 394 serum samples was taken from 204 normal pregnant women at different stages of gestation. The FSH levels remained constant throughout pregnancy and no rise was associated with the late first trimester elevation of human chorionic gonadotrophin (hCG).

The effect of varying prolactin levels on pituitary luteinizing hormone and follicle-stimulating hormone response to gonadotropin-releasing hormone

Seventy-one women with menstrual irregularities were investigated by measurement of basal plasma estradiol, prolactin, and gonadotropin levels. They were each given an intravenous injection of 100 microgram of gonadotropin-releasing hormone (GnRH), and both luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured for two hours. The women were divided into three groups on the basis of the prolactin levels: "normal," "mild elevation," and "severe elevation." For each prolactin group there was no difference in age or estradiol or basal LH and FSH levels. The pituitary response to the GnRH injection was also similar for the three groups. These data suggest that elevated prolactin levels do not interfere with pituitary gonadotropin cell function.

Estrogens delay the postpartum recovery of the LH-RH-induced gonadotropin release

In 27 healthy postpartum women, who were neither lactating nor receiving any therapy, LH-RH stimulation tests (50 micrograms i.v.) were performed on days 7, 14, 21 and 28 of the puerperium. In a second group of 9 postpartum women an i.m. injection of 10 mg estradiol valerianate was administered within the 3rd postpartum day, and an LH-RH stimulation test was performed on days 14 and 21 of the puerperium. Blood was withdrawn at standard intervals and LH and FSH measured by radioimmunoassay. No significant FSH and LH response was found on day 7. On day 14 there was a significant release of FSH but no LH was released. On days 21 and 28 there was a significant release of FSH and LH but the magnitude of the FSH response was greater than that of the LH release. The administration of estrogens did inhibit the recovery of the pituitary from its refractoriness: on day 14 no release of LH and FSH was observed; on day 21, only a significant release of FSH could be detected in the second group of postpartum women. This emphasizes the major role played by steroids in the regulation of the hypothalamo-pituitary-gonadal function.

Basal and LRH-stimulated secretion of FSH during early pregnancy

The gonadotropin response to 25 mug of LH/FSH releasing hormone (LRH) intravenously was investigated during the very first weeks of pregnancy. It was found progressively to decrease, and no response in FSH was found for more than 5 weeks. The basal levels of FSH showed the same decreasing tendency, and a few weeks after conception they were often close to the sensitivity limit of the assay. With this report we have continued our description of the changing pituitary responsiveness to LRH from conception to the puerperium. During later stages of pregnancy the plasma levels of FSH were markedly reduced, and the response was inhibited even after 500 mug of LRH intervenously. The return of the response during the puerperium showed a specific pattern with a dissociation of the response in FSH and LH. No such dissociation was found during the period of progressive inhibition during the very first weeks of pregnancy.

Studies on the gonadotropin response after administration of LH/FSH-releasing hormone (LRH) during pregnancy and after therapeutic abortion in the second trimester

The gonadotropin response to synthetic LH/FSH-releasing hormone (LRH) was found to be suppressed in the second trimester of pregnancy. The basal levels of plasma FSH were very low and no detectable increase occurred after injection of up to 500 mug LRH intravenously. Five of the women were then tested with 25 mug of LRH intravenously on three occasions during the first month after therapeutic abortion in the second trimester. A rapid normalization of the basal plasma levels of FSH and LH and of the response to LRH occurred. This is in contrast with the pattern after term pregnancy. The possible role of different hormones and of the duration of pregnancy (duration of inhibition) as an explanation for this discrepancy are discussed.

Pituitary responses to LRH in the postpartum periods

Pituitary responses to luteinizing-hormone-releasing-hormone (LRH) in the postpartum periods were studied. Following a subcutaneous injection of 100 mug of synthetic LRH to postpartum subjects, no statistically significant changes in the levels of LH and FSH could be demonstrated in five subjects on postpartum day 1 or 3 and the three subjects on postpartum day 8. A normal elevation of LH and FSH following LRH was demonstrated in one subject 36 days post partum. The findings are in agreement with previous studies demonstrating a persistence of pituitary suppression during the early postpartum period. No correlation could be drawn between the pituitary responses to LRH and the plasma levels of estradiol-17 beta and progesterone.

Pituitary gonadotropin responses to synthetic luteinizing hormone-releasing hormone in patients with typical and atypical polycystic ovary disease

Synthetic luteinizing hormone-releasing hormone (LH-RH) was administered intravenously to 17 women with polycystic ovary disease (PPCO), 16 women with hypothalamic amenorrhea (HA), and nine women with normal cycles. The serum levels of follicle-stimulating hormone (FHS) and luteinizing hormone (LH) were measured at frequent intervals before and after LH-RH injection. The PCO patients were arbitrarily divided into two groups on the basis of ovarian morphology. The eight patients with large, "typical" PCO's (Type I) showed a greater LH response and a lower FSH response to LH-RH than did the nine patients with smaller, "atypical" PCO's (Type II). The LH response in Type I co was also greater than that in HA, but the FSH response in both types of PCO was significantly less than that in HA. The gonadotropin responses to LH-RH in Type I PCO were quite similar to those occurring in normal women during the two to three days prededing ovulation. The results suggest that excessive LH secretion and/or impaired FSH secretion may be etiologically significant in PCO but do not clearly differentiate whether the stimulus for this pattern of gonadortopin secretion occurs at the hypothatamic or pituitary level.