Attenuation of gonadotrophin release and reserve in superovulated women by gonadotrophin surge attenuating factor (GnSAF)

In-vivo and in-vitro studies have provided evidence that a non-steroidal ovarian factor, called gonadotrophin surge attenuating factor (GnSAF), attenuates the endogenous LH surge in superovulated women. To study the mechanism of action of GnSAF, the LH response to two i.v. pulses of GnRH (10 micrograms each, 2 h apart) was investigated in eight normally ovulating women during the late follicular phase of a spontaneous and an FSH superovulated cycle. The maximal LH increase in response to the first pulse (initial release) was considered as representing the acutely releasable pool and the delta LH area under the whole curve (integrated response) the reserve pool of LH. Both the initial release and the integrated response to GnRH were markedly attenuated in the FSH as compared to the spontaneous cycles. The response to the second pulse was significantly greater than the response to the first pulse (self-priming effect of GnRH) in both the spontaneous and the FSH cycles. However, in the FSH cycles the self-priming effect of GnRH was markedly reduced as compared to the spontaneous cycles. We conclude that during superovulation induction in women the two pools of pituitary LH are markedly attenuated. It is suggested that GnSAF attenuates both the GnRH-induced initial release of LH and the self-priming effect of GnRH on the pituitary.     

Follicle stimulating hormone stimulates the production of gonadotrophin surge attenuating factor (GnSAF) in vivo

OBJECTIVE: To study the time-course production of gonadotrophin surge attenuating factor (GnSAF) after the onset of FSH treatment in women. DESIGN: Normally cycling women were treated with FSH injections (225 IU per day) starting on cycle day 2 (0800 h). The response of LH to an i.v. injection of 10 micrograms GnRH (GnSAF bioactivity) was investigated 12, 24, 36 and 48 hours after the first FSH injection, as well as during the early follicular phase of an untreated spontaneous cycle. PATIENTS: Six normally ovulating women with long-standing unexplained infertility were studied. The women were used as their own controls during the spontaneous cycles. MEASUREMENTS: Pituitary response to GnRH was calculated as the net increase in LH at 30 min (delta LH30) above the basal value. RESULTS: delta LH30 was significantly attenuated 12, 24, 36 and 48 hours after the first FSH injection as compared to the spontaneous cycles. In the latter cycles, delta LH30 decreased significantly from day 2 (12 hours) to day 4 (48 hours). Serum oestradiol levels at 12 and 24 hours did not differ significantly between the FSH and the spontaneous cycles. CONCLUSIONS: These results demonstrate that in superovulated women, a marked attenuation in the pituitary response to GnRH occurs as early as 12 hours from a single injection of FSH before any significant increase in serum oestradiol levels. It is suggested that FSH is a potent stimulus of GnSAF production in women.     

SUPEROVULATION INDUCTION IN WOMEN SUPPRESSES LUTEINIZING HORMONE SECRETION AT THE PITUITARY LEVEL

In superovulated women the pituitary response to GnRH is markedly attenuated by an unspecified ovarian factor(s). To examine the site of attenuation, the response of the pituitary to GnRH was investigated in five normally ovulating women during the late follicular phase of 3 cycles, i.e. a spontaneous (control) cycle, a cycle treated with 'pure' FSH, and a cycle treated with a combination of 'pure' FSH and pulsatile GnRH, via a pump (15 micrograms/pulse). The oestradiol levels (mean +/- SEM) at the time of the GnRH challenge were respectively 646 +/- 35, 1692 +/- 282 and 5976 +/- 1129 pmol/l. The size of the leading follicle was similar in all groups. Serum LH levels during treatment with FSH decreased significantly, while during treatment with FSH plus GnRH they increased initially and then decreased progressively. The response of pituitary LH to GnRH was significantly attenuated during treatment with FSH and FSH plus GnRH, as compared to the spontaneous cycles, but was not abolished. The attenuation was significantly greater in the FSH plus GnRH cycles (94%) than in the FSH cycles (59%). We conclude that in superovulated cycles, the attenuation of the pituitary response to GnRH increases with the degree of ovarian hyperstimulation. It is suggested that the responsible unspecified ovarian factor(s) exerts its effects at least at the pituitary level.     

Effect of varying concentrations of follicle stimulating hormone on the production of gonadotrophin surge attenuating factor (GnSAF) in women

OBJECTIVE We studied the time-course of production of gonadotrophin surge attenuating factor (GnSAF) in relation to varying serum concentrations of FSH in women. DESIGN Normally cycling women were investigated in four cycles, i.e. a spontaneous cycle treated with placebo (cycle P) and three cycles treated with three different FSH dosages (1 ampoule, cycle 1; 3 ampoules, cycle 3 and 6 ampoules, cycle 6). Placebo or FSH were given as a single i.m. injection on cycle day 2 (0900 h). The response of LH to an i.v. injection of 10 μg GnRH (GnSAF bioactivity) was investigated 4, 8, 12 and 24 hours after the injection of placebo or FSH. PATIENTS Six normally ovulating women with long-standing unexplained infertility were studied. The women were used as their own controls during the cycle treated with placebo. MEASUREMENTS Pituitary response to GnRH was calculated as the net increase in LH at 30 minutes (ΔLH) above the basal value. RESULTS Serum FSH concentrations increased after the injection of FSH in a dose dependent manner. Compared with cycle P, Δ LH was significantly attenuated in cycle 3 and cycle 6 at 8,12 and 24 hours and in cycle 1 at 12 hours after the injection of FSH. Basal concentrations of oestra-diol (E₂) and LH did not differ significantly among the four cycles at any point except in cycle 6 at 24 hours after the FSH injection when E₂ values were significantly higher and LH values significantly lower than in cycle-P. CONCLUSIONS These results suggest that GnSAF bioactivity increases significantly as early as 8 hours from a single injection of FSH before any significant increase in serum E₂ values. We conclude that in women the effect of FSH on the production of GnSAF in the early follicular phase is concentration dependent.     

Effect of follicle stimulating hormone or human chorionic gonadotrophin treatment on the production of gonadotrophin surge attenuating factor (GnSAF) during the luteal phase of the human menstrual cycle

OBJECTIVE Although there is much in-vivo evidence for the existence of a gonadotrophin surge attenuating factor (GnSAF), its source and identity remain unknown. We have studied the control of GnSAF production by FSH and hCG during the luteal phase of the cycle. DESIGN Normally cycling women were investigated in three cycle. Starting on day 5 after the midcycle LH peak, the women received i.m. injections of placebo (1st cycle control), hCG at a dose of 750 IU per day (2nd cycle) and FSH at a dose of 225 IU per day (3rd cycle) for five consecutive days. The response of LH to a single i.v. dose of 10 μg GnRH (GnSAF bioactivity) was investigated several times during the experimental period. PATIENTS Six normally ovulating women with long-standing unexplained infertility were studied. The women were used as their own controls during the cycle treated with placebo. MEASUREMENTS Pituitary response to GnRH was calculated as the net increase in LH at 30 minutes (ΔLH) above the basal value. RESULTS Serum concentrations of FSH and hCG increased significantly during the second and 3rd cycles respectively. Compared with the control cycles, ΔLH was significantly attenuated as early as 12 hours from the onset of FSH injections. In contrast, basal concentrations of oestradiol (E₂) and immunoreactive inhibin started to increase 48 hours after the first injection of FSH, while progesterone values remained similar to those in the controls. During treatment with hCG, no attenuation was seen in ΔLH values, while those of E₂, progesterone and inhibin showed a significant increase. CONCLUSIONS These results demonstrate that during the luteal phase of the human menstrual cycle, FSH, but not LH, stimulates the production of gonadotrophin surge attenuating factor. It is suggested that the source of gonadotrophin surge attenuating factor at that stage of the cycle is a cohort of small follicles rather than the corpus luteum.     

Is the short follicular phase in older women secondary to advanced or accelerated dominant follicle development?

This study sought to determine whether the shortened follicular phase in ovulatory older women is secondary to advanced (i.e. earlier) or accelerated (i.e. more rapid) folliculogenesis. Normal ovulatory women, aged 40-45 yr (n = 15) and 20-25 yr (n = 13), underwent daily venipuncture and transvaginal ultrasonography throughout the follicular phase of a spontaneous menstrual cycle (control cycle) and after pituitary down-regulation with a GnRH agonist (study cycle). As expected, the older subjects in the control cycles demonstrated an elevated d 3 FSH and a shortened follicular phase compared with the younger subjects. After release from hypothalamic-pituitary-ovarian axis suppression, the early follicular phase FSH peak occurred earlier (6.8 vs. 9.8 d; P < 0.01) and was of a greater magnitude (12.1 vs. 6.5 mIU/ml; P < 0.01) in the older subjects. The time from release of suppression until the subsequent LH surge was also shorter (17.5 vs. 20.8 d; P < 0.01) in the older group. However, the time from FSH peak to LH surge was similar in the older and younger groups (10.7 vs. 11.0 d; P = 0.74). Compared with younger women, older subjects had normal follicular phase levels of estradiol and inhibin A and lower levels of inhibin B in both control and study cycles. We conclude that the shortened follicular phase observed in older ovulatory women is due to earlier dominant follicle selection, independent of hormonal influences from the preceding luteal phase.     

CHANGES IN SERUM PROLACTIN LEVELS DURING THE FOLLICULAR PHASE AND THE ENDOGENOUS LUTEINIZING HORMONE SURGE OF CYCLES HYPERSTIMULATED WITH FOLLICLE STIMULATING HORMONE

The pattern of serum PRL levels during superovulation induction with pulsatile 'pure' FSH was investigated in 10 normally ovulating women. They were studied in two consecutive cycles, i.e. an untreated spontaneous and an FSH stimulated cycle. An endogenous LH surge occurred in all 10 spontaneous cycles and in five of the FSH cycles. Midcycle PRL levels were significantly higher in the FSH stimulated than in the spontaneous cycles (P less than 0.01). In both groups of cycles, circadian periodicity of serum PRL levels during the LH surge was different from that during the late follicular phase with higher levels at midnight, although in the FSH cycles PRL secretion showed a sustained increase over 24 h. A nadir of PRL levels was found between 0900 h and 1200 h. In contrast, progesterone secretion during the LH surge showed a nocturnal increase with the highest value between 0600 h and 1200 h and the lowest at midnight. In the FSH cycles without an LH surge, PRL levels increased as long as FSH administration was continued and showed a significant positive correlation with the increasing serum oestradiol levels (r = 0.77). We conclude that ovarian hyperstimulation is a potent stimulus of PRL secretion in women. It is suggested that the midcycle endogenous LH surge facilitates the evening PRL secretion, while induction of multiple folliculogenesis amplifies the 24 h pattern of PRL secretion.     

GnRH secretion throughout the ovine estrous cycle

In order to define the patterns of gonadotropin-releasing hormone (GnRH) secretion during the estrous cycle of the sheep we sampled hypophysial portal blood from conscious animals on day 1 of the cycle (n = 1), during the luteal phase (n = 8), during the follicular phase (n = 6) and during the preovulatory luteinizing hormone (LH) surge (n = 6). At the same time, we sampled jugular blood to measure plasma LH concentrations. During day 1 we noted regular GnRH pulses, whereas GnRH pulse amplitude and frequency were more variable in the luteal phase of the cycle. In the transition from the luteal phase to the follicular phase the GnRH pulse frequency increased and the amplitude decreased. Around the time of the LH surge we noted 3 types of secretory profiles for GnRH. In one sheep (type 1) there was a large GnRH pulse at the onset of the LH surge followed by very little activity during the surge. In two sheep (type 2) the GnRH profile did not change between the late follicular phase and the onset of the LH surge. In the remaining three sheep (type 3) there was a clear increase in the secretion of GnRH at the onset of the LH surge. With the exclusion of the type 1 sheep the GnRH pulse frequency was maximal (2 pulses/h) at the time of the LH surge; average portal GnRH levels were also maximal at this time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute effects of progesterone and the antiprogestin RU 486 on gonadotropin secretion in the follicular phase of the menstrual cycle

Considerable controversy still exists concerning the role of progesterone in the initiation of the midcycle gonadotropin surge in humans. We, therefore, carried out a prospective randomized study to determine the potential of progesterone to initiate a gonadotropin surge and the acute effects of a potent progesterone antagonist (RU 486) on follicular phase gonadotropin secretion in normal women. The women underwent frequent blood sampling for 4 in the midfollicular (day 6) or late follicular phase (day 10). They then received either progesterone (10 mg, im) or RU 486 (10 or 100 mg, orally), and blood sampling was continued for an additional 8 h. Four women received each of the drug regimens in the early follicular phase, and four received each regimen in the late follicular phase. Two additional women were studied as control subjects at each stage of the cycle. Progesterone administration in the mid- and late follicular phases resulted in an acute increase in plasma LH and FSH concentrations, and the increases correlated with the base line plasma estradiol concentrations (P less than 0.05). In contrast to progesterone, the women who received RU 486 in the mid- and late follicular phases had a reduction in plasma LH and FSH concentrations after drug administration. The response in the mid-follicular phase was considerably less than that in the late follicular phase, and the extent of the response correlated with the baseline plasma estradiol concentrations (P less than 0.005). The changes were similar in response to both RU 486 doses. We conclude that progesterone can initiate a gonadotropin surge in the late follicular phase of the menstrual cycle. The inhibitory effect of the progesterone antagonist RU 486 suggests that a positive feedback mechanism involving progesterone may be influential some time before the surge onset.     

Pattern of gonadotropin-releasing hormone (GnRH) secretion leading up to ovulation in the ewe: existence of a preovulatory GnRH surge

We have previously shown LH surges induced by physiological estradiol levels are invariably accompanied by robust and sustained GnRH surges in the ewe. Such an increase, however, has not been observed consistently during the preovulatory LH surge. In the present study, we examined GnRH secretion in Suffolk and Ile de France ewes during the preovulatory period using a method for pituitary portal blood collection which allows simultaneous portal and jugular blood samples to be taken at frequent intervals for up to 48 h. Ewes were sampled either during the mid-late luteal phase (n = 8) or follicular phase (n = 20). During the follicular phase, a robust increase in GnRH secretion occurred at the onset of the LH surge in 11 of 12 ewes sampled during the LH surge. The GnRH increase in most ewes was a massive surge, reaching values averaging 40-fold greater than baseline and extending well beyond the end of the preovulatory LH surge. In the single ewe not exhibiting a GnRH surge during the LH surge, postmortem inspection indicated blood was probably not sampled from the pituitary portal vessels. In the early follicular phase, GnRH-pulse frequency was greater than that observed in the luteal phase and, within the follicular phase, GnRH-pulse frequency increased further and amplitude decreased as the surge approached. These data demonstrate GnRH secretion leading up to ovulation in the ewe is dynamic, beginning with slow pulses during the luteal phase, progressing to higher frequency pulses during the follicular phase and invariably culminating in a robust surge of GnRH. The LH surge, however, ends despite continued elevation of GnRH.     

Use of gonadotropin-releasing hormone agonist to trigger follicular maturation for in vitro fertilization

In spontaneous cycles both LH and FSH are secreted in a surge at midcycle. In in vitro fertilization (IVF) cycles, hCG administration results in elevation of LH-like activity only. The objective of this study was to compare the effectiveness of a single midcycle dose of GnRH agonist with hCG on follicular maturation. Eighteen IVF cycles in 14 women were randomized to receive either 0.5 mg leuprolide acetate or 5000 IU hCG at midcycle. Both groups underwent identical ovarian stimulation and cycle monitoring. On the day of GnRH agonist or hCG administration, estradiol concentrations and the number of follicles 1.5 cm or larger were the same in both groups. Mean serum LH and FSH levels were elevated for 34 h after GnRH agonist administration. In contrast, mean serum hCG levels were elevated for approximately 6 days after the administration of hCG, and serum FSH levels did not change. Mean luteal phase serum estradiol concentrations were lower in the GnRH agonist group than in the hCG group (P less than 0.02). No differences were observed in mean serum progesterone or PRL during the luteal phase or in the length of the luteal phase in the two groups. The mean number of oocytes retrieved and embryo number and quality did not differ between the two groups. Three of nine GnRH agonist cycles and none of nine hCG cycles resulted in clinical pregnancy (P = 0.1). The results of this study indicate that GnRH agonist is able to simulate a midcycle surge of gonadotropins, leading to follicular maturation and pregnancy. Further work is needed to determine whether there is any clinical advantage of GnRH agonist over hCG administration with regard to pregnancy rates.     

Gonadotropin, estrogen and progesterone response to long term gonadotropin-releasing hormone infusion at various stages of the menstrual cycle.

6 normally menstruating women, aged 22-27, were given constant infusions of 12.5-25 mcg/hour gonadotropin releasing hormone (GnRH) for 24 hours during 10 cycles. 4 were infused in the early follicular, 3 in the late follicular, and 3 in the luteal phase. Frequent blood samples were assayed for luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol, progesterone, and GnRH. The increase in gonadotropin and patterns of response varied in the different stages of the cycle. Quantitatively the response was minimal in the early follicular phase, maximal at midcycle, and moderate in midluteal phase. In the latter 2 phases most of the gonadotropins were released during the first 8 hours of infusion. The ratio of the LH-FSH areas under the curves favored FSH in the early follicular phase and LH at midcycle and luteal phase. In all the cycles there was an initial increase in both gonadotropins which lasted 6-8 hours after which the levels declined but nevertheless remained above baseline as long as the infusion was continued. Plasma GnRH measured during 6 infusions was undetectable prior to the starting and after discontinuation of the infusion, but during infusion fluctuations were considerable ranging from 150 to 500 pg/ml. These studies bring additional evidence to the possible existence of 2 gonadotropin pools in the human pituitary and point to the complexity of the response mechanism to GnRH stimulation and its relation to ovarian secretion.     

Circulating immunoreactive inhibin levels during the normal human menstrual cycle

Serum inhibin concentrations were measured daily by RIA in six normal women throughout one menstrual cycle. The RIA was specific for inhibin, and inhibin subunits and related proteins cross-reacted minimally in it. In the early to midfollicular phase, inhibin levels changed little, while in the late follicular phase, inhibin levels rose, in parallel with estradiol (r = 0.43; P less than 0.05; n = 22), to a peak level of 714 (407-1267) U/L (geometric mean +/- 67% confidence limits) coincident with the midcycle LH and FSH surges. An inverse relationship was found between serum inhibin and FSH during the mid- to late follicular phase (r = 0.42; P less than 0.01; n = 45). Inhibin levels rose further during the luteal phase to a peak level of 1490 (1086-2028) U/L 7-8 days after the LH surge, and they correlated positively with serum progesterone (r = 0.76; P less than 0.001; n = 49) and inversely with serum FSH (r = 0.43; P less than 0.01; n = 49) throughout the luteal phase. We conclude that 1) circulating inhibin is detectable throughout the normal menstrual cycle; 2) in the late follicular phase, inhibin levels rise in parallel with estradiol, consistent with the concept that both are products of the maturing follicle; 3) in the luteal phase, the profile of inhibin suggests that it is a secretory product of the corpus luteum; and 4) the inverse relationship between inhibin and FSH in the follicular phase is consistent with the inhibin hypothesis, while at midcycle there is loss of the inhibitory effect of inhibin on FSH secretion. The inverse relationship between FSH and inhibin during the luteal phase suggests a hitherto unsuspected role for inhibin in the feedback regulation of FSH secretion.     

Hypothalamic dysfunction

A pulsatile GnRH stimulus is required to maintain gonadotropin synthesis and secretion. The frequency and amplitude of GnRH pulses determine gonadotropin subunit gene expression and secretion of pituitary LH and FSH. Rapid frequency (more than 1 pulse per h) GnRH pulses favor LH while slower frequencies favor FSH secretion. During ovulatory cycles, an increase in GnRH frequency during the follicular phase favors LH synthesis prior to the LH surge, while following ovulation, luteal steroids slow GnRH pulses to favor FSH synthesis. Thus, a changing frequency of GnRH stimulation of the gonadotrope is one of the mechanisms involved in differential gonadotropin secretion during ovulatory cycles. In hypothalamic amenorrhea a majority of women exhibit a persistent slow frequency of LH (GnRH) pulses, which reflects excess hypothalamic opioid tone and can be temporarily reversed by opioid antagonists. At the other end of the spectrum, in polycystic ovarian syndrome, LH (GnRH) pulses are persistently rapid and favor LH synthesis, hyperandrogenism and impaired follicular maturation. Administration of progesterone can slow GnRH pulse secretion, favor FSH secretion and induce follicular maturation. Thus, the ability to change the pattern of GnRH secretion is an important factor in the maintenance of cyclic ovulation, and loss of this function leads to anovulation and amenorrhea.     

ENDOGENOUS LUTEINIZING HORMONE SURGE IN WOMEN DURING INDUCTION OF MULTIPLE FOLLICULAR DEVELOPMENT WITH PULSATILE FOLLICLE STIMULATING HORMONE

In this study nine consecutive normally cycling women undergoing in-vitro fertilization (IVF) were superovulated with clomiphene citrate followed by pulsatile 'pure' FSH injected s.c. via a pump (28 IU every 3 h). All women displayed an endogenous LH surge, which was markedly attenuated in most of the cases (peak value 44.5 +/- 5.9 U/l, duration 29.2 +/- 1.2 h, mean +/- SEM) as compared to spontaneous cycles. An increase in serum progesterone levels before the onset of the LH surge was seen in only one woman at a time when the LH values were low. During the LH surge serum progesterone levels increased significantly in all patients (12.7 +/- 1.90 nmol/l vs 4.74 +/- 1.57 nmol/l at the onset of the surge, mean +/- SEM, P less than 0.05) indicating follicular luteinization. Very high oestradiol levels in serum were found at the onset of the LH surge (7504 +/- 898 pmol/l, mean +/- SEM). Preovulatory oocytes were recovered from all women through a laparoscope 34-36 h after the beginning of the LH surge and embryos were replaced to them after IVF. One ongoing clinical pregnancy occurred. In contrast to results in monkeys, these results demonstrate for the first time that normally cycling women superovulated with clomiphene pulsatile 'pure' FSH will display an endogenous LH surge. Although the surge is attenuated implantation can occur.     

Progesterone blocks the estradiol-induced gonadotropin discharge in the ewe by inhibiting the surge of gonadotropin-releasing hormone.

Previous studies indicate an elevation of circulating progesterone blocks the positive feedback effect of a rise in circulating estradiol. This explains the absence of gonadotropin surges in the luteal phase of the menstrual or estrous cycle despite occasional rises in circulating estradiol to a concentration sufficient for surge induction. Recent studies demonstrate estradiol initiates the LH surge in sheep by inducing a large surge of GnRH secretion, measurable in the hypophyseal portal vasculature. We tested the hypothesis that progesterone blocks the estradiol-induced surge of LH and FSH in sheep by preventing this GnRH surge. Adult Suffolk ewes were ovariectomized, treated with Silastic implants to produce and maintain midluteal phase concentrations of circulating estradiol and progesterone, and an apparatus was surgically installed for sampling of pituitary portal blood. One week later the ewes were allocated to two groups: a surge-induction group (n = 5) in which the progesterone implants were removed to simulate luteolysis, and a surge-block group (n = 5) subjected to a sham implant removal such that the elevation in progesterone was maintained. Sixteen hours after progesterone-implant removal (or sham removal), all animals were treated with additional estradiol implants to produce a rise in circulating estradiol as seen in the follicular phase of the estrous cycle. Hourly samples of pituitary portal and jugular blood were obtained for 24 h, spanning the time of the expected hormone surges, after which an iv bolus of GnRH was injected to test for pituitary responsiveness to the releasing hormone. All animals in the surge-induction group exhibited vigorous surges of GnRH, LH, and FSH, but failed to show a rise in gonadotropin secretion in response to the GnRH challenge given within hours of termination of the gonadotropin surges. The surges of GnRH, LH, and FSH were blocked in all animals in which elevated levels of progesterone were maintained. These animals in the surge-block group, however, did secrete LH in response to the GnRH challenge. We conclude progesterone blocks the estradiol-induced gonadotropin discharge in the ewe by acting centrally to inhibit the surge of GnRH secreted into the hypophyseal portal vasculature.     

Prolactin-releasing action of a low dose of exogenous gonadotropin-releasing hormone throughout the human menstrual cycle

Pharmacological doses of gonadotropin-releasing hormone (GnRH) are known to induce prolactin (PRL) release in different pathological states. The same effect can be observed in postmenopausal women and during the phases of menstrual cycle characterized by high estrogen levels. With the aim to evaluate whether nonpharmacological doses of GnRH are also able to induce PRL release, gonadotropin and PRL response to a low dose of GnRH (10 micrograms, i.v. bolus) was evaluated in 70 normal women during different phases of their menstrual cycle. A significant PRL increase was observed in 33% of subjects during the first days of the cycle (menstrual phase; days 1-3 from the beginning of menstrual bleeding: n = 6), in 24% of subjects during early follicular phase (days -10 to -8 from LH peak: n = 17); in 38% of subjects during midfollicular phase (days -6 to -4 from LH peak: n = 8); in 78% of subjects during preovulatory phase (days -2 to -1 from LH peak; n = 9); in 67% of subjects during postovulatory phase (days +1 to +2 from LH peak; n = 6) and in 42% of subjects during midluteal phase (days +5 to +8 from LH peak; n = 24). In brief, the increase of mean PRL levels after GnRH administration was only significant (p less than 0.05) during pre- and postovulatory phases. The percentage of patients who showed a PRL response during the different phases of menstrual cycle was significantly correlated to the mean maximal net increase of LH (r = 0.927; p less than 0.01) and to the mean maximal net increase of FSH (r = 0.926; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Decreased release of gonadotropin-releasing hormone during the preovulatory midcycle luteinizing hormone surge in normal women.

To investigate the contribution of hypothalamic gonadotropin-releasing hormone (GnRH) secretion to the midcycle gonadotropin surge in the human, the response of luteinizing hormone (LH) to competitive GnRH receptor blockade achieved by administration of a range of doses of a pure GnRH antagonist was used to provide a semiquantitative estimate of endogenous GnRH secretion. The LH response to 5, 15, 50, and 150 micrograms/kg s.c. of the NAL-GLU GnRH antagonist ([Ac-D-2Nal1,D-4ClPhe2,-D-Pal3,Arg5,D-4-p-met hoxybenzoyl-2-aminobutyric acid6,D-Ala10]GnRH, where 2Nal is 2-naphthylalanine, 4ClPhe is 4-chlorophenylalanine, and 3Pal is 3-pyridylalanine) was measured in normal women in the early and late follicular phases of the menstrual cycle, at the time of the midcycle LH surge and in the early luteal phase. LH decreased in a dose-response fashion after administration of the GnRH antagonist in all cycle phases (P < 0.0001). When this suppression was expressed as maximum percent inhibition, there was no difference in response during the early and late follicular and early luteal phases. However, at the midcycle surge, there was a leftward shift of the dose-response curve with significantly greater suppression of LH at the lower antagonist doses in comparison to the other cycle phases (P < 0.005), but no difference at the highest dose. Thus, we draw the following conclusions. (i) There is a consistently greater degree of LH inhibition by GnRH antagonism at the midcycle surge at submaximal degrees of GnRH receptor blockade than at other phases of the menstrual cycle in normal women. (ii) This leftward shift of the dose-response relationship to GnRH receptor blockade suggests that the overall amount of GnRH secreted at the midcycle surge is less than at other cycle stages. (iii) These data confirm the importance of pituitary augmentation of the GnRH signal at the time of the midcycle gonadotropin surge in the human.     

Gonadotropin-releasing hormone (GnRH) analog suppression renders polycystic ovarian disease patients more susceptible to ovulation induction with pulsatile GnRH

Pulsatile GnRH administration consistently restores normal reproductive hormone levels and ovulation in women with hypogonadotropic hypogonadism, but is less effective in those with polycystic ovarian disease (PCOD). We pharmacologically created a hypogonadotropic condition with a GnRH analog (GnRH-A) in six women with PCOD to investigate the role of deranged gonadotropin secretion in PCOD and to improve the response to pulsatile GnRH ovulation induction. Before GnRH and GnRH-A treatment the women with PCOD had increased LH pulse frequency [one pulse every 55 +/- 2 (+/- SE) min; P less than 0.05] and LH pulse amplitude (10.9 +/- 1.4 U/L; P less than 0.05) compared to normal women in the follicular phase of their menstrual cycle. Each PCOD woman completed one cycle of pulsatile GnRH administration for ovulation induction before (pre-A cycles; n = 6) and one or two cycles after (post-A cycles; n = 9) GnRH-A administration [D-Ser(tBu)6-Des,Gly10-GnRH; 300 micrograms, sc, twice daily for 8 weeks]. Pulsatile GnRH (5 micrograms/bolus) was given at 60-min intervals using a Zyklomat pump. Daily blood samples were drawn during the pulsatile GnRH ovulation induction cycles for the determination of serum LH, FSH, estradiol (E2), progesterone, and testosterone, and pelvic ultrasonography was done at 1- to 4-day intervals. Mean (+/- SE) serum LH levels were elevated during the pre-A cycle (49.2 +/- 3.1 IU/L) and decreased to normal levels during the post-A cycles (19.6 +/- 1.4 IU/L; P less than 0.0001). Mean testosterone concentrations were lower during the post-A cycles [88 +/- 2 ng/dL (3.1 +/- 0.1 nmol/L)] than during the pre-A cycles [122 +/- 3 ng/dL (4.2 +/- 0.1 nmol/L); P less than 0.0001]. In the follicular phase of the post-A cycles E2 levels were significantly lower [81 +/- 5 pg/mL (300 +/- 20 pmol/L) vs. 133 +/- 14 pg/mL (490 +/- 50 pmol/L); P less than 0.0001], preovulatory ovarian volume was smaller (24.6 +/- 2.0 vs. 31.4 +/- 2.4 cm3; P less than 0.01), and the FSH to LH ratio was higher (0.56 +/- 0.03 vs. 0.16 +/- 0.01) than in the pre-A cycle, suggesting more appropriate function of the pituitary-gonadal axis. Excessive LH and E2 responses to pulsatile GnRH administration in the early follicular phase of the pre-A cycle were abolished in the post-A cycles.(ABSTRACT TRUNCATED AT 400 WORDS)     

Follicular fluid treatment during the follicular versus luteal phase of the menstrual cycle: effects on corpus luteum function

Administration of charcoal-extracted porcine follicular fluid (pFF) to rhesus monkeys at the time of menses impairs the subsequent function of the corpus luteum of the menstrual cycle. The following studies were performed: 1) to characterize the luteal phase defect induced by pFF treatment at menses, and 2) to determine whether pFF treatment in the luteal phase alters corpus luteum function. Adult, female rhesus monkeys were injected sc for 3 days with pFF (10, 5, and 5 ml) beginning on day 1 (n = 5) or day 18 (n = 4) of the menstrual cycle. Femoral venous blood was collected daily throughout the treatment cycle and during the posttreatment cycle of day 18 to 20-treated monkeys. Serum LH, FSH, 17 beta-estradiol (E2), and progesterone (P) were measured by RIA. After pFF treatment on days 1-3, FSH and E2 levels in the early follicular phase were less (P less than 0.05) than those of control cycles (n = 7). Serum LH was not suppressed by pFF treatment. Moreover, the preovulatory rise in circulating E2 and the amplitude of the LH/FSH surge were similar in control and pFF-treated monkeys. Although timely midcycle gonadotropin surges occurred in four of five pFF-treated monkeys, serum P was markedly reduced (P less than 0.05) during the first half of the luteal phase. Circulating P increased to control levels during the late luteal phase before normal onset of menses 16.3 +/- 1.0 (SE) days after the LH surge. Treatment with pFF on days 18-20 of the cycle reduced the levels of circulating FSH, but serum LH, E2, P, and the length of the luteal phase remained comparable to control cycles. Moreover, the hormonal patterns and the length of the follicular and luteal phases in the posttreatment cycle indicated normal ovarian function. Thus, pFF treatment at menses results in an aberrant ovarian cycle characterized by an insufficient, rather than short, luteal phase. Whereas pFF treatment in the early follicular phase vitiates development of the dominant follicle and the related corpus luteum, similar treatment at midluteal phase does not suppress concurrent luteal function or subsequent folliculogenesis.