Studies on the decreased gonadotropin response after administartion of LH-FSH-releasing hormone during pregnancy and the puerperium

Significance of the secretion of human prolactin and gonadotropin for puerperal lactational infertility

The causes of puerperal infertility in lactating women are poorly understood. The controlling centres may be either the hypothalamic-pituitary axis or the ovary (or both). We studied the secretory dynamics of prolactin and gonadotropins in healthy, normal, lactating and non-lactating women after administering either gonadoliberin to assess pituitary responsiveness or human menopausal gonadotropins to assess ovarian responsiveness during the puerperium. A reciprocal relationship was observed between the secretion of gonadotropins and the secretion of prolactin after the nipples of mothers who were breast-feeding had been stimulated for 30 min. The absence of a short-loop negative feedback control by prolactin for gonadotropin secretion was not confirmed because cyclic secretion of gonadotropin was not necessarily impaired by hyperprolactinaemia. Hyperprolactinaemia did, however, appear to impair the function of the corpus luteum in women suffering from non-puerperal galactorrhoea. We postulate a multifactorial mechanism for puerperal infertility based initially on the peripheral concentration of prolactin and gonadotropins and, in some poorly defined way, on the cerebral concentration of catecholamines.

Serum inhibin during lactation: relation to the gonadotrophins and gonadal steroids

OBJECTIVE

The aims of the study were to describe the changes in serum immunoreactive inhibin (INH) during normal lactation and to examine the relations between INH, oestradiol (E2) and follicle stimulating hormone (FSH), particularly during the first weeks post partum.

DESIGN

Blood samples were obtained from normally lactating women for hormone measurements at daily intervals until discharge from hospital, and subsequently at weekly intervals until the resumption of menses, or one year post partum.

SUBJECTS

Eighteen breast feeding women aged 27-36 years volunteered for the study.

MEASUREMENTS

INH, FSH, luteinizing hormone (LH), prolactin (PRL), E2, and progesterone (P4) were measured by standard radioimmunoassays. Non-linear modelling was used to quantify the hormone patterns observed.

RESULTS

Hormone levels were compared with those found in the follicular phase of the normal menstrual cycle. Levels of INH fell rapidly in the first week post partum and remained at the lower end of the follicular phase range for the period of study, rising only just prior to resumption of menses. E2 fell more slowly, into the follicular phase range, reaching the lower end of that range only at about approximately 100 days post partum. FSH levels were suppressed initially below the follicular phase range, commencing to rise 4.7-24 days post partum, reaching a plateau high in the follicular phase range 17.5-53 days post partum, and subsequently showing a slow decline. Human chorionic gonadotrophin (hCG), initially measured because of its cross-reactivity in the LH assay, fell rapidly post partum and LH remained in the low follicular phase range for several weeks. PRL fell slowly throughout and was still elevated at 150 days post partum, while P4 fell very rapidly and was less than 1 nmol/l until just prior to first menses.

CONCLUSIONS

Inhibin levels fall rapidly post partum and remain low until close to the time of resumption of follicular activity and menses. The post partum rise in serum FSH appears to be much more closely related to falling oestradiol levels than to the very early and rapid fall in inhibin. Oestradiol thus appears to be the predominant negative feedback factor influencing FSH secretion during the post partum period. The low inhibin levels may allow FSH to rise to levels high in the follicular phase range under the predominant negative feedback control of oestradiol. Inhibin levels do not appear to be a suitable marker of returning fertility.

Priming with gonadotropin-releasing hormone restores gonadotropin secretion during first but not second trimester of pregnancy

This study was designed to determine whether the lack of secretion of endogenous gonadotropin-releasing hormone is the etiology of the hypogonadotropic state of pregnancy. For this purpose, five pregnant women in their first trimester received a single intravenous dose of 150 micrograms of gonadotropin-releasing hormone. Another five women in the first trimester and five women in the second trimester of pregnancy received daily intramuscular injections of 500 micrograms of gonadotropin-releasing hormone for 10 consecutive days. This was followed by a single 150 micrograms gonadotropin-releasing hormone test and then a 24-hour pulsatile infusion of gonadotropin-releasing hormone of 10 micrograms/min/6 min given every hour. Baseline plasma beta-luteinizing hormone and follicle-stimulating hormone were undetectable in all women. Mean +/- SEM plasma beta-human chorionic gonadotropin was significantly higher (p less than 0.001) in the first trimester than in the second trimester, and mean plasma estradiol and prolactin were significantly increased (p less than 0.001 and 0.05, respectively) during the second trimester of pregnancy. After the 10-day treatment with gonadotropin-releasing hormone there was a significant increase (p less than 0.05) in baseline beta-luteinizing hormone and follicle-stimulating hormone only in the first-trimester pregnant women. The single as well as the pulsatile administration of gonadotropin-releasing hormone resulted in a further significant increase in both beta-luteinizing hormone and follicle-stimulating hormone. In contradistinction, women in the second trimester of pregnancy showed a blunted response to the daily and pulsatile administration of gonadotropin-releasing hormone. Since the pituitary secretion of gonadotropin was functionally restored by the administration of exogenous gonadotropin-releasing hormone, possibly there is a lack of secretion of endogenous gonadotropin-releasing hormone during the first trimester of pregnancy. An increased negative feedback produced by increasing levels of plasma estradiol might be the cause of pituitary refractoriness to gonadotropin-releasing hormone during the second trimester of pregnancy.

Postpartum hypogonadotrophinism: evidence for increased opioid inhibition

To investigate a proposed role for endogenous opioids in the inhibition of LH:RH-gonadotrophin release in the postpartum hypogonadotrophic state, LH and FSH responses to naloxone infusion (1.6 mg/h for 2 h) and to a pulse of LHRH (10 micrograms) were measured in five non breast-feeding women. Sequential studies were made at four intervals during the first 25 d postpartum. LH and FSH responses to naloxone were absent on Day 10 postpartum, but significant increments were observed in all studies performed between Days 13-25 postpartum. The relative increments of FSH and LH during naloxone varied as the puerperium progressed; a 3-fold greater release of FSH than LH was found on Day 13 to 15 while the reverse was observed on Day 25. The intermediate days (17-20) yield an equal response. There was a positive linear correlation between the LH and FSH responses to naloxone infusion and to LHRH. These data suggest that the hypogonadotrophinism of the puerperium is due at least in part to increased opioid inhibition of LHRH secretion.

Fertility after childbirth: changes in serum gonadotrophin levels in bottle and breast feeding women

Changes in basal serum gonadotrophin levels during the resumption of ovarian activity post partum have been studied longitudinally in breast and bottle feeding mothers. On the basis of urinary steroid levels, ovarian activity was classified as showing complete suppression, follicular activity only, deficient luteal phases or normal menstrual cycles. Complete suppression of ovarian activity during lactation was associated with normal levels of FSH but low levels of LH. The resumption of follicular development was not accompanied by any increase in levels of either LH or FSH when compared with the phase of complete suppression and this pattern persisted during menstrual cycles characterized by deficient luteal phase progesterone secretion. Basal LH levels did not rise to normal levels during lactation until the resumption of normal ovulatory cycles. FSH secretion remained at a level comparable with the follicular phase of normal ovulatory cycles throughout the post partum period. In mothers who did not breast feed, LH levels rose more rapidly than in breast feeding mothers and had returned to within normal limits by three weeks post partum. At 4 weeks post partum FSH levels were lower in bottle feeding mothers than in breast feeders probably in response to the early rise in oestrogen levels among bottle feeders. These results suggest that decreased LH but not FSH secretion may be important in maintaining infertility associated with breast feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional capacity of the gonadotrophs during pregnancy and the puerperium

The nature of secretion of gonadotropin during pregnancy and the puerperium was determined by measuring plasma levels of beta-subunit luteinizing hormone (GnRH) during the first, second, third trimesters of pregnancy, and at 10 days post partum in lactating and nonlactating women. The nonlactating subjects were divided into two groups according to whether hormonal suppression of lactation was used. Baseline and response levels of beta-LH and FSH after GnRH were below the limits of assay sensitivity (less than 0.5 ng/ml and less than 1.5 mlU/ml, respectively) in all pregnant subjects. In contrast, postpartum lactating and nonlactating subjects who received no hormonal treatment for suppression of lactation had a small but significant increase in FSH after GnRH. In lactating women, FSH increased from 1.5 +/- 0.3 mlU/ml to 2.7 +/- 0.3 mlU/ml (p less than 0.05); and in nonlactating subjects, FSH increased from undetectable levels to 2.0 +/- 0.4 mlU/ml (p less than 0.001). Patients who received estrogenic compounds for suppression of lactation had undetectable FSH baselines and no response after GnRH. beta-LH in both lactating and nonlactating women had a variable but not a significant response to one administration of GnRH. In conclusion, our findings indicate that the functional capacity of the gonadotrophs recovered earlier (at 10 days) than previously reported (less than 14 days) after term pregnancy, and the recovery of FSH secretion occurs earlier and is more consistent than the recovery of beta-LH.

Oestrogen-gonadotrophin feedback mechanisms in the puerperium

The effect of oestradiol benzoate on serum gonadotrophin concentrations before and after LHRH administration was studied in lactating and non-lactating women at 3 and 6 weeks post-partum. Except in the non-lactating women at 6 weeks, basal serum FSH concentrations were suppressed by oestrogen. There were no significant changes in basal concentrations of LH after oestrogen in the lactating women in either the 3- or 6-week studies. Individual increases in the basal LH concentrations in two out of six non-lactating subjects in the 6-week study occurred but overall there were no significant changes. In the 6-week study amplification of the LH response to LHRH was found in both groups, the effect being significantly greater in the non-lactating women. Overall FSH responses were also significantly different in the two groups, being suppression in those lactating ad amplification in those not lactating. The LH/FSH ratios following LHRH administration in the 6-week non-lactating study were similar to those seen in the early follicular phase in regularly menstruating subjects. The basal ratios in the lactating subjects were, however, significantly less than those seen in the non-lactating subjects both at 3 and 6 weeks. This difference was associated with the relative enhancement of LH release in non-lactating subjects and enhancement of FSH release in those lactating. Taken together the results indicate the presence of an intact negative feedback of oestrogen on gonadotrophin release in both groups being enhanced at 6 weeks post-partum in the lactating subjects; also in the lactating subjects at 6 weeks there was less amplification by oestrogen of the responsiveness of the anterior pituitary to LHRH. At 6 weeks, however, in the non-lactating group these responses were similar to those seen in normal regularly menstruating subjects. These dynamic endocrine studies suggest a possible hypothalamic-pituitary mechanism which may help to explain the delayed return of ovulatory cycles in lactating women.

Activation of pituitary gonadotropic function by an agonist of luteinizing hormone-releasing factor in the puerperium

To test the hypothesis that long-term deprivation of endogenous luteinizing hormone-releasing factor (LRF) during the course of pregnancy may account for the lack of gonadotropin in the puerperium, six normal postpartum women were treated with the potent and long-acting LRF agonist (D-Trp6, Pro9-NEt)-LRF. A 50 microgram dose of LRF agonist was administered subcutaneously every 48 hours for four doses, with the first dose given on the first day post partum. Prior to treatment, each subject was tested with two pulses of LRF (10 micrograms at 2 hour intervals) and again at the end of LRF agonist treatment on day 10 post partum. Pulses of LRF induced no significant elevation of follicle-stimulating hormone (FSH) levels on day 1 post partum. During treatment, a significant (P less than 0.005) increase in basal FSH levels occurred after the second dose of LRF agonist administration. Following treatment, pulses of LRF elicited a remarkable gonadotropin release with a relatively greater percent rise for FSH than for human chorionic gonadotropin-luteinizing hormone. Our data indicate that the lack of gonadotropin activity during the first 3 weeks post partum is, at least in part, related to insufficiency of endogenous LRF secretion and that resumption of gonadotropin secretion can be functionally activated by treatment with the appropriate dose and intervals of an LRF agonist.

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.

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.

Ectopic secretion of chorionic gonadotropin by a lung carcinoma. Pituitary gonadotropin and subunit secretion and prolonged chemotherapeutic remission

The ability of tumor markers to improve cancer therapy is not established. We studied a man with a human chorionic gonadotropin (HCG)-secreting large cell carcinoma of the lung and gynecomastia. Preoperatively, levels of HCG (109 ng/ml), its alpha and beta subunits (3.2 and 21 ng/ml, respectively) and plasma estradiol were elevated. Despite apparently complete tumor resection and total resolution of gynecomastia, HCG titers remained elevated (3.3 ng/ml), heralding tumor recurrence three weeks later. Because the pathophysiologic consequences of the ectopic secretion of HCG on pituitary function are not established, we administered 100 microgram of gonadotropin-releasing hormone (LHRH) and observed a markedly delayed increase in pituitary gonadotropins. Early chemotherapy, guided by persistence of HCG, reduced HCG to undetectable levels, restored to normal the response to LHRH and resulted in a distinctly unusual 30-month complete remission. Use of HCG as a tumor marker levels is more sensitive than the symptom of gynecomastia and may permit detection of small, potentially curable tumor foci.

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.

Release of prolactin during pregnancy: effect of sulpiride

The aim of this trial was to study the prolactin-releasing capacity of the pituitary during pregnancy by means of an acute stimulation with sulpiride. Thirty women with normal pregnancies were included in the study (first trimester, nine women; second trimester, eleven women thir trimester, ten women). Each woman received an intramusclar injection of 100 mg of sulpiride sulfate between 8 and 9 A.M. Three similar groups received injections of a saline solution. Blood samples were obtained before and 30 and 60 minutes after the injection. In each sample the prolactin concentration was determined by radioimmunoassay. Basal prolactin levels increased during pregnancy. Significant responses to sulpiride were observed during the three stages of pregnancy, and the levels in the second and third trimesters were higher than those in the firsttrimester. The prolactin-releasing capacity of the pituitary, as judged by the response to sulpiride, seems to be maintained during pregnancy.

Pituitary response to luteinizing hormone-releasing hormone after induced abortion in the first and second trimesters

Luteinizing hormone-releasing hormone (LHRH) (100 microng) was administered subcutaneously to healthy female volunteers 2 and 4 weeks after induced abortion in the first trimester (group A) and the midtrimester (group B). Four patients were studied in each group. The response to LHRH was determined in terms of plasma LH and follicle-stimulating hormone levels. Adequate pituitary response occurred in subjects of group A at both 2 and 4 weeks. In group B pituitary unresponsiveness was found at 2 weeks which persisted to some extent at 4 weeks. These data are in accord with the pituitary unresponsiveness observed after termination of pregnancy at term and suggest that the duration of pregnancy has an influence on the development of this unresponsiveness.

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.