Pulsatile gonadotropin secretion in women with hypothalamic amenorrhea: evidence that reduced frequency of gonadotropin-releasing hormone secretion is the mechanism of persistent anovulation

Hypothalamic amenorrhea (HA) is a clinical disorder of unknown etiology. The diagnosis is made by exclusion of known abnormalities of pituitary and ovarian function. To determine if abnormalities of GnRH secretion could account for the anovulation and amenorrhea, we measured plasma gonadotropins every 20 min for 10- to 24-h periods in 19 women with HA. Ovarian steroids and gonadotropin responses to an iv bolus dose of GnRH (25 ng/kg) were also measured. The results were compared to those obtained during the early follicular (EF) and late luteal (LL) phases of ovulatory cycles in normal women. Plasma estradiol was lower (mean +/- SE, 52 +/- 5 pg/ml) than either cycle stage in normal women. Mean plasma LH was lower than EF values and FSH was higher than LL values. The amplitude of LH pulses in HA was similar to that in normal women. LH pulse frequency was the same as that present during the LL, but lower than that during the EF (HA, 4.7 pulses/12 h; EF, 7.7 pulses/12 h; P less than 0.05). In addition to the similar frequency, the patterns of LH secretion in HA resembled that of LL in that the amplitude of LH pulses was highly variable and pulses occurred at irregular intervals. Consistent changes in diurnal gonadotropin secretion were not found, and LH secretion was greater at night in 9 studies and during the day in 5 studies. Repeat studies in three patients (5-13 months later) revealed that LH pulse frequency was variable, being unchanged in 1, increased in 1, and decreased in the third patient. Thus, LH pulse frequency and, by inference, GnRH pulse frequency are similar in HA to those in the normal luteal phase despite a different steroid milieu. GnRH pulse frequency increases from the luteal to the follicular phases of normal cycles and may be important in the initiation of ovarian follicular maturation. These data suggest that the absence of cyclical gonadotropin secretion and anovulation in HA result from a decreased frequency and irregular amplitude of GnRH secretion and consequent absence of ovarian follicular maturation.     

Successful use of pulsatile gonadotropin-releasing hormone (GnRH) for ovulation induction and pregnancy in a patient with GnRH receptor mutations

GnRH receptor mutations have recently been identified in a small number of familial cases of nonanosmic hypogonadotropic hypogonadism. In the present report we studied a kindred in which two sisters with primary amenorrhea were affected with GnRH deficiency due to a compound heterozygote mutation (Gln(106)Arg, Arg(262)Gln) and performed extensive phenotyping studies. Baseline patterns of gonadotropin secretion and gonadotropin responsiveness to exogenous pulsatile GnRH were examined in the proband. Low amplitude pulses of both LH and free alpha-subunit (FAS) were detected during 24 h of every 10 min blood sampling. The proband then received exogenous pulsatile GnRH i.v. for ovulation induction, and daily blood samples for gonadotropins and sex steroids were monitored. At the conventional GnRH replacement dose for women with hypogonadotropic hypogonadism (75 ng/kg), no follicular development occurred. At a GnRH dose of 100 ng/kg, the level and pattern of gonadotropin secretion more closely mimicked the follicular phase of normal women; a single dominant follicle was recruited, and an endogenous LH surge was elicited. However, the luteal phase was inadequate, as assessed by progesterone levels. At a GnRH dose of 250 ng/kg, the gonadotropin and sex steroid dynamics reproduced those of normal ovulatory women in both the follicular and luteal phases, and the proband conceived. The FAS responses to both conventional and high dose GnRH were within the normal range. The following conclusions were made: 1) Increased doses of GnRH may be used effectively for ovulation induction in some patients with GnRH receptor mutations. 2) Higher doses of GnRH are required for normal luteal phase dynamics than for normal follicular phase function. 3) Hypersecretion of FAS in response to exogenous GnRH, which is a feature of congenital hypogonadotropic hypogonadism, was not seen in this patient with a GnRH receptor mutation.     

The effect of naloxone on endogenous opioid regulation of pituitary gonadotropins and prolactin during the menstrual cycle

To determine the influence of ovarian sex steroid hormones on endogenous opioid regulation of pituitary FSH, LH, and PRL secretion, six women were studied during the follicular phase (days 8-9) and luteal phase (days 21-23) of their menstrual cycles. An iv bolus dose of 10 mg of the opiate antagonist naloxone was given, and plasma FSH, LH, and PRL were measured at -30, -15, 0, 15, 30, 45, 60, 90, 120, and 180 min. During the follicular phase, baseline plasma FSH and LH levels were 10.7 +/- 0.9 and 16.7 n+/- 2.0 mIU/ml (mean +/- SEM), respectively; the plasma PRL level was 11.7 +/- 1.2 ng/ml. Naloxone did not significantly alter plasma FSH, LH, or PRL during the follicular phase. Basal levels of LH were significantly lower during the luteal phase than during the follicular phase (P less than 0.01). During the luteal phase, plasma LH increased significantly from a basal level of 10.0 +/- 1.0 to 20.8 +/- 3.0 mIU at 30 min (P less than 0.001) and remained significantly elevated at 90 min. Similarly, plasma PRL increased significantly from a basal level of 11.0 +/- 0.7 to 16.2 +/- 2.7 ng/ml at 30 min (P less than 0.025), but decreased by 90 min to 12.5 +/- 1.5 ng/ml. Plasma FSH did not change after naloxone treatment. Our results suggest that endogenous opiates have a prominent inhibitory effect on pituitary gonadotropin and PRL secretion only during the luteal phase of the menstrual cycle.     

Periovulatory plasma prolactin response to gonadotropin-releasing hormone: role of endogenous opiates

It has been previously shown that in normal women during the periovulatory period, prolactin (PRL) levels increase after the administration of nonspecific stimuli, such as growth hormone-releasing hormone or gonadotropin-releasing hormone (GnRH). In order to gain insight into the mechanism of this response, we have tested the effect of a naloxone infusion (1.6 mg/h) on the PRL response to GnRH in 5 normal females, aged 20-27 years, tested during the periovulatory period. Naloxone was administered starting 60 min before GnRH administration (100 micrograms as an i.v. bolus). Naloxone clearly blunted the PRL response (basal 10.7 +/- 1.7 ng/ml, peak 11.8 +/- 0.2 ng/ml at 30 min, versus: basal 9.0 +/- 0.5 ng/ml, peak 20.6 +/- 3.9 ng/ml at 45 min after GnRH alone; significance of difference between peaks: p less than 0.05). A secondary late increase of PRL levels was observed, reaching about 60% of basal levels at 120 min (16.8 +/- 2.6 ng/ml). These data indicate that periovulatory PRL dynamics are altered by naloxone administration and suggest a possible involvement of opioid peptides in the 'paradoxical' PRL response to GnRH in normal subjects.     

Follicular stimulation versus ovulation induction in juvenile primates: importance of gonadotropin-releasing hormone dose

We evaluated the dose of GnRH administered by 1-min pulsatile infusion necessary to achieve follicle growth vs. the dose needed for ovulation induction. Doses of 6.0, 0.6, and 0.06 micrograms GnRH were given to juvenile monkeys iv in 1 min once per h for 4 consecutive months. Monkeys receiving hourly 6.0-micrograms doses of GnRH had cyclic elevations of serum estradiol and had menses, but did not ovulate, as evidenced by lack of a corpus luteum at laparoscopy and consistently low progesterone concentrations. These monkeys ovulated only when hCG was administered near midcycle as a surrogate LH surge. In contrast, monkeys receiving 0.6-microgram doses of GnRH frequently had normal ovulatory menstrual cycles and characteristic elevations of progesterone during the luteal phase. Typically, juvenile monkeys receiving hourly 0.06-microgram doses of GnRH initially had development of a dominant follicle contemporaneous with a rise of serum estradiol, but never ovulated or had any subsequent follicular growth or elevated steroidogenic activity. In summary, ovarian follicular development and steroidogenesis in juvenile monkeys can be initiated by doses of GnRH ranging from 0.06-6.0 micrograms/h, although spontaneous ovulation and normal luteal function occurred frequently only with the 0.6 micrograms/h pulses of GnRH. Thus, the dose range of pulsatile GnRH needed for follicle growth is much broader than that required for induction of ovulatory menstrual cycles.     

Effects of different gonadotropin pulse frequencies on corpus luteum function during the menstrual cycle of rhesus monkeys

In the nonfertile menstrual cycle, the frequency of episodic LH secretion declines from approximately 1 pulse/h in the early luteal phase to 1 pulse/4-8 h in the mid- to late luteal phase, but the relevance of this phenomenon to the initiation of functional luteal regression is not completely understood. We investigated whether a reduction in LH pulse frequency causes a decline in luteal progesterone production by experimentally reducing LH pulse frequency during the early luteal phase, and measured the effects on the subsequent plasma progesterone pattern and the onset of luteal regression. Rhesus monkeys were rendered anovulatory by placing radiofrequency lesions in the arcuate region of the medial basal hypothalamus or surgically transecting the hypothalamic-pituitary stalk. Endogenous gonadotropin secretion and ovulatory menstrual cycles were restored by pulsatile infusion of synthetic GnRH at a frequency of 1 pulse/h. Commencing on days 3-6 of the luteal phase, GnRH frequency was changed to either 1 pulse/8 h (four animals) or 1 pulse/24 h (four animals), or maintained at the standard 1 pulse/h frequency (four animals). Luteal phases of 13- to 17-day duration were observed in all animals kept on the 1 pulse/h frequency and in three of four animals in which the frequency was changed to 1 pulse/8 h on day 3 of the luteal phase. Daily midluteal phase (days 5-10) plasma progesterone levels observed in response to the 1 pulse/h and 1 pulse/8 h infusion regimens were similar (mean +/- SE, 4.1 +/- 0.4 vs. 3.2 +/- 0.4 ng/ml; P greater than 0.1). In contrast, short luteal phases were observed in all animals after the LH pulse frequency was reduced to 1 pulse/24 h. Comparison of plasma LH responses to a representative GnRH pulse of each GnRH infusion regimen revealed that the maximal LH levels attained in response to 1 pulse/8 h (47.5 +/- 11.5 ng/ml) were significantly greater (P less than 0.05) than the maximal LH levels attained in response to 1 pulse/h (30.5 +/- 3.2 ng/ml) or 1 pulse/24 h (27.2 +/- 5.0 ng/ml). Progesterone levels remained elevated for 140-200 min after the LH pulse resulting from the 1 pulse/8 h infusion regimen. In response to the 1 pulse/24 h infusion regimen, plasma progesterone levels remained elevated for 60 min after the LH pulse.(ABSTRACT TRUNCATED AT 400 WORDS)     

Subcutaneous administration of gonadotropin-releasing hormone: absorption kinetics and gonadotropin responses

To evaluate the suitability of the sc route for the pulsatile delivery of GnRH, plasma GnRH, LH, and FSH levels were measured by RIA in five women with hypothalamic amenorrhea after sc injection of single doses of 2.5, 5, and 10 micrograms GnRH. The results were compared with those obtained after bolus iv injection of 10 micrograms GnRH. After sc injection, plasma GnRH levels rose to a dose-related maximum after 5-10 min and fell to less than 10% of the peak value by 90 min. The mean plasma disappearance half-time was 24 min (range, 18-30 min). After bolus iv injection, an initial rapid phase of disappearance (t1/2, 2.8 min) was followed by a slower phase (t1/2, 33 min), falling within the 95% confidence intervals for the disappearance half-time after sc administration (12-36 min). The patterns of LH response to sc and iv GnRH were similar, with maximum levels reached between 20 and 30 min after injection, then declining to 50-69% of the peak value by 90 min after sc injection and 61% of the peak value 90 min after iv injection. There was no significant difference between peak LH responses to 10 micrograms iv and sc doses of GnRH [15.2 +/- 2.5 (+/- SEM) vs. 13.2 +/- 2.2 IU/L]. Subcutaneous administration of three consecutive GnRH pulses at 90-min intervals to four women resulted in gonadotropin responses to each GnRH pulse. We conclude that sc GnRH administration results in pulsatile plasma GnRH and gonadotropin responses, the latter resembling those seen after iv GnRH. These results confirm the suitability of the sc route for pulsatile GnRH delivery.     

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)     

Insulin sensitivity during the menstrual cycle

Sensitivity to insulin (euglycemic clamp technique) and serum estradiol and progesterone levels were measured in seven normal nonobese women, aged 19-23 yr, during the follicular and luteal phases of the menstrual cycle. The mean serum progesterone level was 1.2 +/- 0.1 (+/- SE) nmol/liter in the follicular and 24.2 +/- 7.7 nmol/liter in the luteal phase (P less than 0.02). Mean plasma insulin was maintained at 84 +/- 6 and 86 +/- 3 mU/liter and mean plasma glucose at 4.6 +/- 0.1 and 4.6 +/- 0.1 mmol/liter during the insulin clamps in the follicular and luteal phases, respectively. The rate of glucose metabolism averaged 9.0 +/- 1.3 mg/kg X min in the follicular phase and 9.2 +/- 1.6 mg/kg X min (P = NS) during the luteal phase. These results indicate that insulin-mediated glucose metabolism, as determined by the euglycemic clamp technique, is unaffected by the phase of the menstrual cycle in normal women.     

Inadequate corpus luteum function in benign breast-diseases (author's transl)]

The amount of progesterone and estradiol secreted by human corpus luteum depends upon an adequate release of FSH and LH by pituitary gland during follicular phase and ovulation. In this paper, plasma determination of progesterone and estradiol were carried out in 109 women with benign breast disease during the luteal phase of their menstrual cycle. Results obtained were compared with those observed in 25 normal women studied in the same conditions. In women with benign breast disease, the curve of daily progesterone concentrations during luteal phase was lower than that of normal women. The progesterone peak at 5th day of luteal phase was only 8,1 +/- 3.8 ng/ml instead of 17.2 +/- 3.5 ng/ml in normal women. No significative difference was observed concerning plasma estradiol between patients and normal women. These results indicate that women with benign breast disease have an inadequate corpus luteum function which may be the result of disorder of ovulation. Pathophysiological implications resulting from this observation are discussed.     

Gonadotropin-releasing hormone pulsatile administration restores luteinizing hormone pulsatility and normal testosterone levels in males with hyperprolactinemia

Hyperprolactinemia in men is frequently associated with hypogonadism. Normalization of serum PRL levels is generally associated with an increase in serum testosterone (T) to normal. To determine the mechanism of the inhibitory effect of hyperprolactinemia on the hypothalamic-pituitary-gonadal axis, we studied the effect of intermittent pulsatile GnRH administration on LH pulsatility and T levels in four men with prolactinomas. All patients had high PRL values (100-3000 ng/ml), low LH (mean +/- SEM, 2.2 +/- 0.1 mIU/ml), and low T values (2.3 +/- 0.3 ng/ml), with no other apparent abnormality of pituitary function. GnRH was administered iv using a pump delivering a bolus dose of 10 micrograms every 90 min for 12 days. No LH pulses were detected before treatment. Pulsatile GnRH administration resulted in a significant increase in basal LH levels (6.7 +/- 0.6 mIU/ml; P less than 0.001) and restored LH pulsatility. In addition, T levels increased significantly to normal values in all patients (7.8 +/- 0.4 ng/ml; P less than 0.001) and were normal or supranormal as long as the pump was in use, although PRL levels remained elevated. These data, therefore, suggest that hyperprolactinemia produces hypogonadism primarily by interfering with pulsatile GnRH release.     

The roles of estradiol and progesterone in decreasing luteinizing hormone pulse frequency in the luteal phase of the menstrual cycle

During the luteal phase of the menstrual cycle, plasma progesterone (P) and estradiol (E2) concentrations are elevated, and LH (and by inference GnRH) pulse frequency is slow. In contrast, LH pulse frequency increases during the early follicular phase when plasma E2 and P are lower. To examine the mechanism(s) responsible for the slower GnRH pulse frequency in the luteal phase, we maintained plasma P, E2, or both at midluteal concentrations from the midluteal phase to the time of the next early follicular phase and measured the effects on LH secretion. Thirteen normal women with regular menstrual cycles were studied during two or three cycles. Blood was obtained every 10 min during 10-h studies. Control cycle luteal and early follicular studies were followed by a second control study in the luteal phase of the treatment cycle. P (six women), E2 (seven women), or both (five women) then were given twice daily by im injection for 6-12 days until the day corresponding to the early follicular study of the control cycle (EF + P, EF + E2, or EF + E2 + P). A final study was performed 1 week after the injections were discontinued (F). LH pulse frequency was low in the midluteal phase [3.2 +/- 0.2 (+/- SE) pulses/10 h] and increased by the early follicular phase (8.0 +/- 0.8 pulses/10 h) in the control cycles. The increase in LH pulse frequency was not significantly inhibited by administration of P (6.7 +/- 0.7 pulses/10 h; EF + P). However, during both E2 alone and E2 + P, LH pulse frequency remained low (EF + E2, 3.6 +/- 0.8; EF + E2 + P, 2.0 +/- 0.7 pulses/10 h). The mean plasma FSH concentrations paralleled changes in LH pulse frequency, increasing from the luteal to the early follicular phase in the control cycles and during P injections and remaining low during E2 and E2 + P injections. We conclude that continued exposure to P alone does not maintain GnRH pulse frequency at midluteal phase values and that any effect of P requires the presence of E2. As E2 alone maintained lower LH pulse frequency, E2 may act directly to decrease the pulsatile GnRH secretion or it may potentiate the effects of low (less than 3.2 nmol/L) P concentrations.     

Pulsatile secretion of chorionic gonadotropin during the normal menstrual cycle

Several groups of investigators have previously reported that small amounts of hCG are present in blood and urine of nonpregnant eugonadal women and men. We have developed highly sensitive and specific, two-monoclonal antibody, sandwich-type assays which can quantify both hCG and LH in sera from postmenopausal women, women at all phases of the menstrual cycle, and men. Using these assays we have also reported that hCG is secreted in a pulsatile fashion in postmenopausal women, is stimulated by GnRH in both men and postmenopausal women, and is suppressed by a GnRH agonist in castrate men. Employing these same sandwich assays, we report herein that hCG is secreted in a pulsatile manner during the follicular and luteal phases of the normal menstrual cycle. During the follicular phase 0.68 +/- 09 (+/- SEM) pulses of hCG occurred each hour, while 0.62 +/- 0.08 pulses of LH occurred. Pulse durations during the follicular phase for hCG and LH, respectively, were 38.3 +/- 4.4 and 62.5 +/- 11.1 min (P less than or equal to 0.05). During the luteal phase there were 0.42 +/- 0.16 pulses/h of hCG and 0.38 +/- 0.08 pulses of LH (P greater than 0.05). Pulse durations were 22.3 +/- 7.5 and 126.4 +/- 19.0 min for hCG and LH, respectively (P less than 0.01). The t1/2 of hCG disappearance was 37.2 +/- 3.8 min during the follicular phase and 22.9 +/- 4.6 min during the luteal phase. The t1/2 values of LH were 82.9 +/- 5.7 and 67.5 +/- 5.12 min during follicular and luteal phases, respectively. The t1/2 of LH was greater than the t1/2 of hCG (P less than 0.01). We conclude that small amounts of hCG are secreted in a pulsatile manner during follicular and luteal phases of the human menstrual cycle.     

Corpus luteum insufficiency induced by a rapid gonadotropin-releasing hormone-induced gonadotropin secretion pattern in the follicular phase

The pulse frequency of LH and FSH (and by inference, GnRH) is a major determinant of the relative baseline plasma levels of LH and FSH. Luteal phase deficiency has been reported to be associated with increased gonadotropin pulse frequency and inadequate preovulatory follicular development. In this study we induced in normal women a supraphysiological gonadotropin pulse frequency in the follicular phase to determine its effect on follicular development and corpus luteum function. Specifically, we tested the hypothesis that a supraphysiological GnRH pulse frequency would result in deficient luteal phase production of progesterone. The subjects were six normal ovulatory women (age range, 23-35 yr). They were initially studied during a control cycle (cycle 1). Then, 25 ng/kg GnRH was administered iv every 30 min from the early follicular phase of the next cycle (cycle 2) until ovulation occurred. GnRH administration resulted in increased follicular phase plasma LH and FSH levels and LH to FSH ratios, multiple preovulatory follicles (mean, 2.8) with increased mean integrated estradiol [1302 (pg/mL)day (cycle 1) vs. 2550 (pg/mL)day (cycle 2); P less than 0.05; 4780 vs. 9360 (pmol/L)day, Systeme International units], spontaneous ovulation, decreased luteal phase plasma immunoreactive and bioactive LH levels, decreased luteal phase length [13.5 days (cycle 1) vs. 8.8 days (cycle 2); P less than 0.05], and decreased mean integrated progesterone secretion [152 (ng/mL)day (cycle 1) vs. 66 (ng/mL)day (cycle 2); P less than 0.01; 482 vs. 209 (nmol/L)day, Systeme International units]. We conclude that high frequency LH and FSH secretion during the follicular phase can induce inadequate progesterone secretion during the subsequent luteal phase, and we infer that the pathophysiological basis for this induced luteal phase deficiency is decreased LH support of corpus luteum function.     

Circulating nitric oxide in women affected by weight loss amenorrhea during pulsatile gonadotropin-releasing hormone therapy

No specific markers of the severity or prognosis of hypothalamic-pituitary-gonadal axis disturbances associated with weight loss amenorrhea (WLA) are currently available. Circulating nitric oxide (NO), which is involved in the control of the reproductive function in women and is correlated with body mass index (BMI), at least in over-weight and obese subjects, might be a marker of the severity and/or progression of WLA. To test this hypothesis, we studied circulating NO levels in 11 women (age 27.1 +/- 1.59 yr) affected by WLA for 5.1 +/- 1.0 yr; in all patients hormonal therapy had been discontinued 10.0 +/- 3.15 months earlier. NO, determined by measuring its stable catabolite nitrite/nitrates (NOx), was compared with some clinical parameters and sex hormone levels. Subsequently, changes in NOx during pulsatile GnRH therapy (120 ng/kg bw sc every 120 min) were compared with the clinical and hormonal data. Fifteen normal women (27.3 +/- 1.6 yr) served as a control group. NOx was significantly lower (p<0.01) in WLA (8.8 +/- 2.0 micromol/l) than in control (18.7 +/- 2.5 micromol/l) subjects. No correlation between NOx and clinical parameters was noted in either WLA or control subjects. As a result of GnRH therapy, ovulatory cycles reappeared in 91% of WLA women. During the 1st cycle, periovulatory 17beta-estradiol levels were 110% higher than those noted in controls. During the 2nd cycle, NOx showed a slight increase in the follicular phase (+12% vs 1st cycle) followed by a drop during the luteal phase (-40% from the follicular phase); indeed, at that time, NOx correlated negatively with progesterone in both WLA (rS -0.32, p<0.05) and control (rS -0.48, p<0.05) subjects. NOx correlated with BMI at the time of the 2nd cycle (rS 0.71, p<0.05). In conclusion, this study shows that in WLA patients: 1) NO is low, as in other conditions of chronic anovulation; 2) it does not correlate with clinical data; 3) it takes longer than sex steroids to increase and show normal-like fluctuations; 4) its fluctuations are restored earlier in patients with greater BMI.     

The effect of luteal phase estrogen antagonism on luteinizing hormone pulsatility and luteal function in women

Pulsatile LH secretion was studied to determine if the frequency of LH pulses was altered by the administration of clomiphene citrate (CC; 150 mg) for 5 days during the midluteal phase of the menstrual cycle. Seven normal women received CC or placebo in alternate cycles in a randomized double blind fashion. On the day after drug administration, blood samples were obtained at 15-min intervals for 8 h for serum LH determinations. Daily blood samples were also obtained throughout the luteal phase for determination of serum LH, estradiol (E2), and progesterone. LH pulse frequency increased from 2.4 +/- 0.5 (+/- SEM)/8 h after placebo to 3.9 +/- 0.6/8 h (P less than 0.01) after CC treatment, but pulse amplitude did not change. The transverse mean of serum LH was higher after CC (13.6 +/- 0.5 mIU/ml) than after placebo (8.4 +/- 0.3 mIU/ml; P less than 0.001), and luteal phase length was increased from 13.5 +/- 0.5 to 16.0 +/- 0.4 days (P less than 0.001) by administration of CC. Luteal phase levels of E2 and progesterone measured daily were significantly elevated (P less than 0.01) in CC-treated cycles. These findings suggest that CC increases the frequency of hypothalamic GnRH secretory episodes, perhaps by an action involving a decrease in endogenous opioid peptide activity. Since peripheral progesterone levels were elevated in the CC-treated cycles, E2 may play a permissive role in the ability of progesterone to increase endogenous opioid peptide activity acutely. Furthermore, since the luteal phase was significantly prolonged by an increase in endogenous LH pulse frequency, the slow frequency of LH pulses in the normal late luteal phase may contribute to the onset of luteolysis in the human.     

Effect of histamine on basal and TRH/LH-RH-stimulated PRL and LH secretion during different phases of the menstrual cycle in normal women

The neurotransmitter histamine (HA) may participate in the regulation of some pituitary hormones. We, therefore, investigated the effect of HA (50 micrograms/kg body weight/h, infusion 0-240 min) on basal and thyrotropin-releasing hormone (TRH) and luteinizing hormone releasing hormone (LH-RH) stimulated prolactin (PRL) and LH secretion in 5 normal women during the early follicular and the luteal phases of the same menstrual cycle. HA had no effect on the basal secretion of the two hormones. However, the PRL response to 200 micrograms TRH during the HA infusion was significantly increased compared to the response to a saline control infusion during the early follicular phase (peak responses were 1,902 +/- 398 vs. 1,228 +/- 230 microIU/ml, p less than 0.025) and during the luteal phase (peak responses were 2,261 +/- 335 vs. 1,647 +/- 245 microIU/ml, p less than 0.05). HA potentiated the LH response to 100 micrograms LH-RH during the early follicular phase (peak responses were 37.1 +/- 4.9 vs. 26.9 +/- 4.5 mIU/ml, p less than 0.05) and during the luteal phase (peak responses were 79.3 +/- 22.5 vs. 50.7 +/- 11.4 mIU/ml, p less than 0.025). We, therefore, found HA to have a potentiating effect on TRH/LH-RH-stimulated PRL and LH secretion in women. The results are similar to our previous findings in men, although the potentiating effects of HA were higher in women.     

Effects of N-methyl-D,L-aspartic acid on luteinizing hormone secretion in normal mice and in hypogonadal mice with fetal preoptic area implants

Many aspects of reproductive function are corrected in hypogonadal mice with preoptic area grafts (HPG/POA). Gonadotropin release and gonadal development are dependent on the presence of GnRH cells within the grafts and GnRH innervation of the median eminence. This study examined the effect of a known modulator of GnRH secretion, N-methyl-D,L-aspartic acid (NMA), in adult normal and HPG/POA male and female mice. All HPG/POA males had significant testicular development after graft surgery, and most HPG/POA females were in constant vaginal estrus and showed ovarian and uterine development; a few also demonstrated ovulatory cyclicity after pregnancies initiated by reflex ovulation. Groups of normal and HPG/POA males that were intact (INT) or castrated (CX) 7 days before testing were challenged with saline, NMA (20 mg/kg), and GnRH (100 ng/0.1 ml). Sequential blood samples from awake animals were obtained via intracardiac catheters for evaluation of plasma LH. There were significant increases in plasma LH after NMA challenge in normal INT [n = 15; 0 min, 0.26 +/- 0.02 (mean +/- SE); 10 min, 1.20 +/- 0.10 ng/ml; P less than 0.05] and normal CX (n = 13; 0 min, 0.36 +/- 0.06, 10 min, 3.25 +/- 0.27). Plasma LH secretion in response to NMA was significantly correlated (r = 0.786; P less than 0.001) with plasma LH release after the GnRH challenge in normal males. In contrast, only 3 of 17 HPG/POA (1 INT and 2 CX) showed increased circulating LH after NMA challenge, despite heightened pituitary sensitivity to GnRH. Normal and HPG/POA female mice were ovariectomized (OX) or OX and estrogen primed (OXE2) 7 days before testing. Intact cycling normal and cycling HPG/POA mice were tested in estrus (EST). There was a greater response to NMA in normal OX (n = 8; 0 min, 0.39 +/- 0.02; 10 min, 1.44 +/- 0.28) than in OXE2 (n = 13; 0 min, 0.29 +/- 0.01; 10 min, 0.52 +/- 0.07) despite similar gonadotroph sensitivity to GnRH. There was also a significant increase in plasma LH in response to NMA in HPG/POA-OX (n = 7; 0 min, 0.50 +/- 0.10; 10 min, 1.62 +/- 0.22) and HPG/POA-OXE2 (n = 12; 0 min, 0.39 +/- 0.04; 10 min, 1.31 +/- 0.26). Plasma LH levels after NMA treatment were significantly correlated with responses to GnRH in female HPG/POA (r = 0.58; P less than 0.03), but not in normal females. Neither normal-EST nor HPG/POA-EST had increased LH release after NMA challenge, perhaps due to the low gonadotroph sensitivity in this state.(ABSTRACT TRUNCATED AT 400 WORDS)     

Long-term administration of gonadotropin-releasing hormone in men with idiopathic hypogonadotropic hypogonadism. A model for studies of the hormone's physiologic effects

The effect of long-term administration of gonadotropin-releasing hormone (GnRH) for induction and maintenance of sexual maturation was characterized in 23 men with idiopathic hypogonadotropic hypogonadism. Twenty-two men achieved normal adult male serum testosterone concentrations (575 +/- 33 ng/dL; p less than 0.0001 compared with the baseline mean of 61 +/- 6 ng/dL) that were sustained in 21 men for up to 36 months with bolus doses of GnRH varying from 25 to 300 ng/kg body weight administered every 2 hours. Pulsatile luteinizing hormone (LH) secretion occurred in all 23 men, with mean levels of LH (14.7 +/- 1.3 mlU/mL) and follicle-stimulating hormone (11.3 +/- 1.3 mlU/mL) within or above the normal range for adult men. Mature sperm were observed in the ejaculates of 20 men, with counts ranging from less than 1 X 10(6) to 96 X 10(6)/mL. Increasing responsiveness of the pituitary-gonadal axis to GnRH was shown in 6 men. Men with idiopathic hypogonadotropic hypogonadism present a useful model to study the onset and maintenance of reproductive function in men.     

The influence of dieting on the menstrual cycle of healthy young women

Nine normal young women of normal weight, aged 20-29 yr, who had regular menstrual cycles, dieted for 6 weeks (approximately 800-1000 kcal/day) and lost between 6 and 8 kg body wt. Half-hourly blood samples were taken from 1800-0530 h on two occasions before and after 1, 2, 3, 4, 5, and 6 weeks of dieting. In three women with anovulatory cycles the LH secretion pattern was not altered by dieting, but plasma estradiol levels decreased and reached menopausal concentrations during the final 2 weeks of dieting. In two of these three women the menstrual cycles were disrupted and regular cycles occurred only 3 and 6 months after dieting. Six women had regular ovulatory cycles. High progesterone values (greater than 3 ng/ml) were recorded in two cycles before the dieting period. While dieting, three women maintained ovulatory cycles and three women had no periovulatory hormone secretion pattern and/or a pattern characteristic of the luteal phase. No significant alterations of average LH concentrations and LH peak frequency developed. It is concluded that mild dieting does not suppress LH secretion in the manner found in anorexia nervosa or during total fasting. Dieting may interfere with gonadal steroid production, thus causing disturbances of the menstrual cycle. The effect described here may be responsible for the early onset of amenorrhea in patients with beginning anorexia nervosa.