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 luteinizing hormone-releasing hormone (LHRH) agonist [D-Trp6-Pro9-NEt]LHRH increased rather than lowered LH and alpha-subunit levels in a patient with an LH-secreting pituitary tumor

Episodic secretion of LH, and the responses of serum LH, alpha-subunit, and testosterone concentrations to the acute administration of LHRH and the chronic administration of the LHRH agonist analog [D-Trp6-Pro9-NEt]LHRH (D-Trp6-Pro9) were evaluated in a 33-yr-old man previously reported to have an LH-secreting pituitary tumor unaccompanied by FSH hypersecretion. Basal serum LH and alpha-subunit concentrations were elevated [57 +/- 0.7 (SEM) mIU/ml (range, 45-71) and 26 ng/ml, respectively]. Frequent sampling revealed six LH secretory spikes over a 24-h period with increments above basal levels varying from 23-40% and interspike intervals ranging from 1.5-5 h. The concentrations of LH or alpha-subunit after iv administration of 150 micrograms LHRH did not increase above these intrinsic LH secretory increments (delta LH: 23%; delta alpha-subunit: 21%). The low basal serum FSH concentrations (3.5 mIU/ml) and elevated basal serum testosterone levels (1480 ng/dl) were unchanged after LHRH. Administration of clomiphene citrate produced no increase in serum LH, FSH, or testosterone concentrations. An attempt was made to decrease LH secretion in this patient using D-Trp6-Pro9. Administration of 200 micrograms daily sc of this LHRH analog for 21 days was associated with increases in serum LH and alpha-subunit concentrations. Mean serum LH and alpha-subunit levels for the 21 days of analog administration were 110 +/- 5.4 (SEM) mIU/ml (range, 70-170) and 64 +/- 3 (SEM) ng/ml (range, 32-84), respectively. During the 9-day period after discontinuance of the LHRH analog, levels of both serum LH and alpha-subunit declined precipitously and mean serum LH and alpha-subunit levels were 58 +/- 7 (SEM) mIU/ml (range, 18-90) and 22 +/- 3 (SEM) ng/ml (range, 12-44), respectively. We conclude that this patient's pituitary tumor has diminished responsiveness to acute LHRH administration and that the effect of chronic D-Trp6-Pro9 is stimulatory rather than inhibitory, as occurs after chronic administration of this analog to normal subjects. The blunted responsiveness to LHRH administration and the lack of response to clomiphene citrate suggest tumor autonomy. The presence of modest paradoxical responsiveness of serum LH and alpha-subunit concentrations during the course of daily D-Trp6-Pro9 administration suggests that central regulatory mechanisms, if present, are abnormal.     

Ovulation induction with pulsatile gonadotropin-releasing hormone and continuous human menopausal gonadotropin in polycystic ovarian disease

Various treatments have been applied to polycystic ovarian (PCO) type of anovulation. However, none of them was definitive in terms of the efficacy and side effects. Six anovulatory women of PCO type were treated with pulsatile gonadotropin-releasing hormone (GnRH) of various pulse intervals and continuous human menopausal gonadotropin (hMG). The efficacy and rationale of the treatments were discussed. The subjects were diagnosed PCO by GnRH test and/or laparoscopy. They did not ovulate with clomiphene, clomiphene-hCG and hMG-hCG therapies. Their pretreatment serum FSH and LH levels and FSH/LH ratios were 6.9 +/- 1.2 mIU/ml, 15.7 +/- 5.1 mIU/ml, and 0.54 +/- 0.19 (Mean +/- SD), respectively. The treatment consisted of 3 protocols: 1) pulsatile GnRH (5-10 micrograms/pulse) of 90 min interval, 2) pulsatile GnRH (5-10 micrograms/pulse) of 120 min interval and 3) continuous hMG (150 IU/day) through subcutaneous route. Follicular growth was monitored sonographically and an intramuscular bolus of 10,000 IU hCG was given when the dominant follicle reached 20 mm in diameter. During both GnRH treatments serum FSH levels and FSH/LH ratios did not elevate substantially. Serum LH, E2 and PRL levels elevated acutely and transiently during the initial phase of GnRH treatments. Follicular growth was observed in a small fraction of the cases, but none of them ovulated. In contrast, continuous hMG treatment induced significant elevation in serum FSH levels (8.2 +/- 1.7 mIU/ml; p less than 0.01) and FSH/LH ratios (1.73 +/- 0.57; p less than 0.001). Transient hyperprolactinemia was accompanied with the preovulatory E2 rise. All the cases ovulated and 3 singleton pregnancies followed. These findings draw conclusions as follows. Pulsatile GnRH administration may desensitize the pituitary presumably due to increased GnRH pulse frequency as a consequence of two independent pulse generators, intrinsic and exogeneous. It may induce transient hyperprolactinemia through a paracrine system between gonadotrophs and lactotrophs. As a due course pulsatile GnRH therapy is questionable for ovulation induction in cases with functioning hypothalamic-pituitary axis. The fact that continuous hMG effectively induced follicle maturation with elevated FSH/LH ratios suggested that FSH dominance might be a prerequisite for folliculogenesis. The fluctuating nature of gonadotropins might not be mandatory for folliculogenesis.     

Use of GnRH agonist and human chorionic gonadotrophin tests for differentiating constitutional delayed puberty from gonadotrophin deficiency in boys

OBJECTIVES: The differentiation of constitutional delayed puberty (CDP) from gonadotrophin deficiency (GD) in boys at referral poses a difficult challenge. The effectiveness of the GnRH agonist (GnRH-a) test in distinguishing between the two conditions was evaluated and compared with findings of the GnRH and hCG stimulation tests. PATIENTS, METHODS AND DESIGN: The study sample included 32 prepubertal boys aged 14 years or older. Thirteen entered spontaneous puberty within 1 year of referral (group A) and 19 remained prepubertal (group B). All underwent the GnRH test (Relefact, Hoechst AG, 0.1 mg/m2 i.v. in one bolus), GnRH-a test (Decapeptyl, Ferring GmbH, 0.1 mg/m2 s.c.) and hCG stimulation (Chorigon, Teva, 1500 units i.m. on three alternate days) at 1-week intervals. All tests were performed at referral at 0800 h. Blood samples were collected before testing and at 30 and 60 min (GnRH test) or 4 h (GnRH-a) for LH and FSH determination, and before testing and at 4 h (GnRH-a) or on the seventh day (hCG) after stimulation for serum testosterone measurement. RESULTS: The LH response to GnRH-a and the testosterone response to hCG stimulation were significantly higher in group A (LH, mean +/- SD 20.4 +/- 7.5 mIU/ml, range 10.8-32.6; testosterone, mean +/- SD 18.0 +/- 5.9 nmol/l, range 9.4-26, P < 0.0001) than in group B (LH, mean +/- SD 2.3 +/- 2.0 mIU/ml, range 0.7-6.9; testosterone, mean +/- SD 1.0 +/- 0.7 nmol/l, range 0.7-3.2), with no overlap between the groups. The cut-off for the LH response to GnRH-a was 8.0 mIU/ml, and for the testosterone response to hCG, 8 nmol/l. There were also significant differences between the groups in mean basal serum LH and FSH (LH, 1.1 +/- 0.5 vs. 0.6 +/- 0.2 mIU/ml, P < 0.05; FSH, 2.2 +/- 2.0 vs. 0.4 +/- 0.3 mIU/ml, P < 0.02) and their response to GnRH (LH, 11.4 +/- 4.4 vs. 2.7 +/- 1.1 mIU/ml, P < 0.0001; FSH, 5.1 +/- 3.4 vs. 2.5 +/- 2.4 mIU/ml, P < 0.0001), and mean serum testosterone level at 4 h after GnRH-a administration (1.9 +/- 1.0 vs. 0.9 +/- 0.4 nmol/l, P = 0.002), but all showed a great overlap in range. Mean age, testicular volume and basal serum testosterone levels were similar in the two groups at referral. One year later, the testicular volume of group A (5.0-12.0 ml) was significantly larger than that of group B (1.0-3.0 ml, P < 0.0001), which remained unchanged on re-examination 3.0 +/- 0.5 years later. CONCLUSIONS: The GnRH-agonist test and the repeated-injection hCG test are reliable diagnostic tools for differentiating CDP from GD in boys.     

CHANGES IN THE RESPONSIVENESS OF LUTEINIZING HORMONE SECRETION TO INFUSION OF THE OPIOID ANTAGONIST NALOXONE THROUGHOUT MALE SEXUAL MATURATION

The present study investigated the time of male sexual maturation during which hypothalamic inhibitory opioid activity can be detected. Normal prepubertal (Tanner stage G 1 (Ts-G1) (n = 4], early pubertal (Ts-G2 (n = 5], pubertal (Ts-G3 (n = 4), and Ts-G4 (n = 2] and adult subjects (Ts-G5 (n = 4] receives a rapid infusion of the selective opiate antagonist nalocone (NAL) (20 mg over 10 min). LH secretion was assessed by frequent (every 10 min for 2 h) venous sampling before and after administration of the opiate blocker, as well as by the LH response to exogenous GnRH. All but one (a Ts-G2 subject) pubertal boys showed aprompt and sustained increase in serum LH concentrations after NAL administration, as disclosed by the areas under the LH curve (aLHc) calculated from samples obtained before and after NAL infusion (aLHc in four Ts-G2 responders, 162 +/- 20 (mean +/- SEM) vs 314 +/- 56 mIU/ml/min before and after NAL respectively, P less than 0.025; Ts-G3, 227 +/- 35 vs 362 +/- 56 mIU/ml/min, P less than 0.025; Ts-G4 and Ts-G5, 432 +/- 77 vs 687 +/- 91 mIU/ml/min, P less than 0.05). In contrast, none of the prepubertal children had significant changes in LH secretion after the NAL challenge (154 +/- 17 vs 154 +/- 9 mIU/ml/min). Although all NAL responders exhibited serum testosterone (T) levels above 5 nmol/l, a positive correlation between individual T values and magnitude of LH responses to NAL was not found. All subjects had significant serum LH increments after GnRH administration. In a second series of studies, additional groups of Ts-G1 subjects were primed during 5 days either with GnRH alone or with GnRH plus sex steroids (ethinyl oestradiol 12.5 micrograms/12 h or testosterone enanthate 1.8 mg/kg body weight (single dose], before NAL administration, to investigate whether hypothalamic opioid activity might be unmasked by additional sex steroids. None of the priming schemes significantly modified the pituitary LH responses to NAL infusion (GnRH-primed group, 145 +/- 48 vs 139 +/- 43 mIU/ml/min before and after NAL, respectively; GnRH plus ethinyl oestradiol-primed group, 124 +/- 42 vs 107 +/- 34 mIU/ml/min; GnRH plus testosterone enanthate-primed group, 64 +/- 10 vs 57 +/- 24 mIU/ml/min). This study suggests that the development and/or maturation of the opioid control of LH secretion is temporally related with the onset of puberty.(ABSTRACT TRUNCATED AT 400 WORDS)     

Low serum bioactive luteinizing hormone in nonorganic male impotence: possible relationship with altered gonadotropin-releasing hormone pulsatility

We determined the biological activity of serum LH in 23 men, aged 25-50 yr, complaining of nonorganic impotence of at least 1-yr duration and 20 normal men. All of the impotent men had normal general physical examinations, penile Doppler tests, psychological tests, and peripheral nerve conduction. Serum PRL, FSH, LH, and thyroid hormone concentrations were normal as were the results of provocative tests of TSH, gonadotropin, and PRL secretion. The mean serum immunoreactive LH (I-LH) levels, measured in each impotent and normal man in three samples taken at 15-min intervals, were similar [7.2 +/- 0.5 (+/-SE) vs. 6.4 +/- 0.5 mIU/mL (IU/L)]. In contrast, the mean serum bioactive LH (B-LH) level was significantly lower in the impotent men than in the normal men [15.9 +/- 2.1 (+/-SE) vs. 33.0 +/- 2.8 mIU/mL (IU/L); P less than 0.05], as was the LH bio- to immunoactive (B/I) ratio (2.1 +/- 0.2 vs. 5.6 +/- 0.5; P less than 0.02). The mean serum testosterone level in the impotent men, although all individual values were within the range of normal for our laboratory [200-900 ng/100 mL (693-3120 nmol/L)], was 25% lower than that in the normal men [347 +/- 23 vs. 450 +/- 26 ng/100 mL; P less than 0.05 (1204 +/- 81 vs. 1560 +/- 91 nmol/L)]. In addition, a significant positive correlation was found between serum testosterone levels and LH B/I ratios in the impotent men (r = 0.45; P = 0.029). Pulsatile LH secretion, measured in six impotent and four normal men in blood samples collected every 15 min for 6 h, was similar in the two groups. The mean serum I-LH levels were similar [7.5 +/- 1.1 (+/-SE) vs. 5.1 +/- 1.0 mIU/mL (IU/L)], while the mean serum B-LH level as well as the LH B/I ratio was significantly lower in the impotent men throughout the observation period [11.4 +/- 2.0 (+/-SE) vs. 26.0 +/- 3.2 mIU/mL (IU/L) and 1.4 +/- 0.2 vs. 5.4 +/- 0.6; P less than 0.05 and P less than 0.02, respectively]. The B-LH pulse amplitude in the impotent men was reduced [mean peak LH, 8.6 +/- 0.3 vs. 25.3 +/- 4.0 mIU/mL (IU/L); P less than 0.05], while the LH pulse frequency was similar in the two groups. The median intrapulse LH B/I ratios were significantly higher than the median interpulse ratios in both impotent (P = 0.02) and normal men (P = 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)     

Repetitive infusion of gonadotropin-releasing hormone distinguishes hypothalamic from pituitary hypogonadism.

Patients who have severe hypogonadotropic hypogonadism caused by presumed hypothalamic disease often have a subnormal LH response to a bolus dose of gonadotropin-releasing hormone (GnRH). To determine if this subnormal response is the result of lack of exposure of the pituitary gonadotroph cells to GnRH, five such men were given daily infusions of 500 microgram GnRH, for 7 days. A standard 250-microgram bolus test dose of GnRH was administered before and again immediately after the week of GnRH infusions. Five men who had severe hypogonadotropic hypogonadism as a result of presumed pituitary disease also received daily GnRH infusions for 1 week. The mean incremental LH responses (+/- SE) to GnRH of the men with presumed hypothalamic disease were 5.0 +/- 1.9 mIU/ml before and 56.9 mIU/ml after the week of infusions. The mean incremental LH responses of the men with presumed pituitary disease were 2.4 +/- 0.7 mIU/ml before and 3.7 +/- 2.9 mIU/ml after the week of infusions. These data suggest that the normal gonadotroph requires prolonged exposure to GnRH for LH responsiveness to become normal, but that the severely damaged gonadotroph cannot be stimulated to release LH normally even by the same prolonged stimulation with GnRH.     

QUANTITATIVE AND QUALITATIVE CHANGES IN LH SECRETION FOLLOWING PULSATILE GnRH THERAPY IN A MAN WITH IDIOPATHIC HYPOGONADOTROPHIC HYPOGONADISM

The pattern of bioactive and immunoreactive LH secretion before and during pulsatile GnRH therapy (18 micrograms/90 min) in a hypogonadotrophic hypogonadal male has been studied. Before treatment the patient was azoospermic and had low testosterone (1.2 nmol/l) with low and apulsatile immunoreactive LH (1.9 +/- 0.2 IU/l) and FSH (1.4 +/- 1.9 IU/l) levels. There was no detectable LH bioactivity. During the first 24 h of GnRH therapy there was a small increase in immunoreactive (5.4 +/- 0.8 IU/l) and bioactive (6.7 +/- 1.3 IU/l) LH, with an irregular pattern and little effect on testosterone production (2.2 nmol/l). Within 1 week of treatment both bioactive (30.5 +/- 6.8 IU/l) and immunoreactive (13.6 +/- 1.5 IU/l) LH levels were above the normal range and the pattern of secretion was pulsatile. The bioactive to immunoreactive (B:I) LH ratios within the pulses (2.6 +/- 0.3) were higher (P less than 0.01) than between pulses (1.97 +/- 0.1) and the testosterone concentration (17.8 +/- 2.1 nmol/l) was now normal. At one month LH secretion was similar and testosterone pulses of high amplitude were evident corresponding to high-amplitude bioactive LH pulses. By 3 months mature spermatozoa (1.3 x 10(6)/ml) were seen in the patient's semen. The pattern of LH secretion was pulsatile but the levels of bioactive (13.1 +/- 3.6 IU/l) and immunoreactive (9.5 +/- 1.3 IU/l) LH decreased towards the normal range reflecting maturation of the testicular feedback control at the pituitary level. This effect was more pronounced on bioactive rather than immunoreactive LH secretion (57% vs 32% relative decrease). At 6 months LH levels were similar and the sperm count was normal (34 x 10(6)/ml).     

Induction of spermatogenesis in isolated hypogonadotropic hypogonadism with exogenous human chorionic gonadotropin

A 21-year old male patient with isolated hypogonadotropic hypogonadism (IGD) is described. Basal serum levels of testosterone (0.5 ng/ml), FSH (2.1 mIU/ml) and LH (2.3 mIU/ml) were low and did not respond to administration of clomiphene citrate. The FSH and LH responses to LHRH were normal. Pituitary-thyroid and pituitary-adrenal function as well as GH reserve were also normal. However, prolactin (PRL) response to both TRH and metoclopramide were blunted compared with normal male subjects. The patient was treated with human chorionic gonadotropin (HCG). Within 20 months he developed full testicular maturation with spermatogenesis and full androgenization. Serum testosterone levels rose to 6.5-13.5 ng/ml. Both basal serum PRL levels and the response to TRH and metoclopramide became normal. Spermatogenesis and androgenization proceeded in the absence of FSH. These results suggest further trials of treatment with HCG alone in patients with IGD are warranted.     

Return of gonadal function in men with prolactin-secreting pituitary tumors

Gonadal function was evaluated in 10 men [33 +/- 17 (SD) yr] with pituitary tumors and hyperprolactinemia (47-2550 ng/ml) using nocturnal penile tumescence (NPT), semen analysis, urinary LH and FSH excretion, and diurnal variation of serum testosterone and PRL. Results were compared to 16 normal subjects (33 +/- 13 yr). NPT was decreased in tumor patients as demonstrated by reduced maximum circumference change (P less than 0.01) and total tumescence time (P less than 0.05). Semen analysis was examined in 5 patients able to produce specimens. All seminal parameters were significantly abnormal as demonstrated by oligospermia, asthenospermia, teratospermia , and elevated fructose. Urinary LH [570 +/- 72 (SE) vs. 838 +/- 22 mIU/h; P less than 0.01] and serum testosterone (235 +/- 60 vs. 625 +/- 63 ng/dl; P less than 0.01) were decreased in 9 tumor patients, all of whom had serum PRL levels above 50 ng/ml. Diurnal variation of serum PRL was absent in hyperprolactinemic patients whereas all had normal circadian changes in serum testosterone, although at a lower set point. Eight patients were followed for 6-13 months after reduction of serum PRL by surgery and/or drug therapy. Serum PRL reached normal levels in six men after 6 months of treatment. Selected individuals had an increase in serum LH after 2 months of treatment. Significant rises in serum testosterone occurred as early as 3 months and normal levels were found in six patients after 6-8 months of treatment. Only two subjects, however, demonstrated a normal semen analysis. These data suggest that men with serum PRL levels above 50 ng/ml maintain a normal diurnal pattern of serum testosterone at a lower set point, and demonstrate hypogonadism with reduced urinary LH excretion and NPT. In addition, routine seminal parameters are clearly abnormal and are both delayed and incomplete in their recovery.     

Gonadotropin determinations and thyrotropin-releasing hormone and luteinizing hormone-releasing hormone testing in critically ill postmenopausal women with hypothyroxinemia

Critically ill patients often have altered serum levels of thyroid hormones. The present study was undertaken to further define hormonal changes in such patients. Since postmenopausal women have normally elevated gonadotropin levels, this group was chosen as the study population. Thirteen critically ill patients with serum T4 concentrations below 5 micrograms/dl (group I), 16 critically ill patients with T4 concentrations of 5 micrograms/dl or greater (group II), and 19 normal subjects (group III) were studied. Basal gonadotropin levels (FSH and LH) were significantly lower (P less than 0.01) in both critically ill groups. The LH level in group I was 36.5 +/- 39.3 (+/- SD) mIU/ml, in group II it was 45.3 +/- 30.4, and in group III it was 75.3 +/- 24.4. The FSH level in group I was 43.0 +/- 39.7 (+/- SD) mIU/ml, in group II it was 78.0 +/- 37.9, and in group III it was 133.0 +/- 38.2. Most group I patients had LH and FSH concentrations far below the normal postmenopausal range. The response to dynamic testing with TRH and LRH revealed a significantly lower incremental TSH response to TRH in group I (8.0 +/- 5.6 mIU/ml) compared to that in group III (13.7 +/- 2.8; P less than 0.05). However, the maximal responses of FSH and LH to LRH were not different between groups I and III, despite the fact that 2 of 10 group I patients had no response. These data indicate that a subset of patients with the low T4 syndrome have hypogonadotropism, inappropriate to their menopausal state. This suggests that acute critical illness may cause hypothalamic or pituitary dysfunction, only part of which is recognized as the low T4 syndrome. The mechanism for this dysfunction and its importance in contributing to the overall mortality in this group is unknown.     

Prepubertal treatment of rats with clomiphene citrate affects postpubertal testicular development

A previous study showed that clomiphene citrate (clomiphene) reduced serum and pituitary gonadotropins and impaired testis growth and steroidogenesis in 10-day-old rats treated for up to two weeks. The present study was conducted to assess the effect of prepubertal clomiphene treatment on postpubertal pituitary-testicular function. Rats were implanted with pellets that released 0, 0.05, 0.5 or 5.0 mg clomiphene.kg-1.day-1 between 10-31 days of age and were killed at 90 days of age. Testis and prostate weights in treated rats were reduced (P less than 0.05), whereas serum LH, FSH and testosterone, and pituitary gonadotropin and GnRH receptor concentrations had recovered to levels observed in control rats. Testicular FSH receptor concentrations were not altered; however, FSH receptor content was decreased (P less than 0.05) in clomiphene-treated rats proportional to the reduction in testicular weight. In contrast, testicular LH and GnRH receptor concentrations were increased (P less than 0.05) in treated animals, resulting in similar receptor contents. Daily sperm production per gram of parenchyma was unaffected, while daily sperm production per testis was decreased in treated rats (P less than 0.05). These data show early postnatal treatment with clomiphene does not permanently impair pituitary function. Despite reduced testicular mass, normal serum testosterone concentrations and testis LH receptor content of treated rats suggest recovered Leydig cell function. The decreased content of testicular FSH receptors and reduced sperm production suggest seminiferous tubule function was compromised in the adult rat.     

Pituitary gonadotropin-releasing hormone receptor regulation in mice. I: Males

The regulation of pituitary GnRH receptors (GnRH-R) has been examined in male mice (C3H/HeH/101H F1 hybrid) after castration and testosterone replacement. GnRH-R were quantified in individual mouse pituitaries by equilibration with 125I(D-Ser(tBut)6) des Gly10 GnRH N ethylamide and compared with serum and pituitary LH and FSH concentrations. The equilibrium association constant was 2.7 X 10(9) M-1 for both intact and castrated male mouse pituitary GnRH-R. Six hours after orchidectomy there was a transient 50% reduction in GnRH-R; 13.6 +/- 3.8 fmol/pituitary (castrate) vs. 25.4 +/- 2.5 (intact). A subsequent partial return of binding sites began at 12 h, reaching a peak value of 18.2 +/- 1.5 fmol/pituitary (33% increase vs. 6 h) at 24-h post orchidectomy. This was followed by a gradual decrease in GnRH-R, reaching a plateau by 72 h. The decrease in GnRH-R was associated with a rapid (6-12 h) increase in serum LH and serum FSH. The pituitary GnRH-R concentration remained 45% below intact control values for up to 3 months and was accompanied by a persistent 5-fold rise in serum LH values. Treatment of male mice with testosterone propionate (TP), 25 micrograms/day, completely prevented the GnRH-R fall and the serum and pituitary LH responses to castration, whereas 12.5 micrograms/day TP produced variable results and 5 micrograms/day TP were ineffective. In another strain of mouse (BALB/c white). GnRH-R values also fell by 66% at 7 days post orchidectomy, with no change in the receptor affinity. In mice with androgen resistance from birth due to absence of androgen receptors (Tfm mice), GnRH-R were 14.45 +/- 0.49 vs. 19.8 +/- 1.67 fmol/pituitary in normal male littermates, and serum LH was 472 +/- 78 ng/ml compared with 52.5 +/- 11.7 ng/ml in normals. These findings are qualitatively similar to those in orchidectomized normal adult mice. Thus, in contrast to reports in rats, pituitary GnRH-R content falls after orchidectomy in mice. Possible explanations for this consistent finding include: persistent receptor occupancy by increased endogenous GnRH secretion, endogenous GnRH-induced receptor loss (down-regulation), or a species difference in the pituitary GnRH-R response to removal of negative steroid feedback, unrelated to changes in endogenous GnRH secretion.     

Absence of hypogonadism in a male patient with a giant prolactinoma: a clinical paradox

BACKGROUND: Impotence and decreased libido are the cardinal features of prolactinomas in males. We describe the unusual clinical, pathological and biochemical features in a male patient with a giant prolactinoma and normal gonadal function. CASE REPORT: A 57 year-old man presented with visual symptoms related to a 30x25x60mm tumor of the sella and skull base. Biopsy revealed a pituitary adenoma and subsequent hormone profiles demonstrated grossly elevated serum prolactin (131,412ng/ml), LH at the upper limit of normal and normal testosterone. The patient had no symptoms of decreased libido or impotence related to this giant prolactinoma. Immunohistochemistry revealed a tumor that was positive for prolactin, alpha-subunit and LH. Cabergoline greatly reduced prolactin levels but these remained above normal. LH, testosterone and alpha-subunit levels were decreased in parallel. Loss of libido and impotence became apparent when testosterone fell below normal, a situation that resolved with further cabergoline treatment and prolactin inhibition and testosterone therapy. CONCLUSIONS: Sexual dysfunction is a hallmark of prolactinomas in males. Tumors that co-secrete prolactin and LH are extremely rare and this is the first such case reported in an adult male. In this case, normal testosterone was maintained by intact LH levels even in the face of the highest prolactin level reported to date.     

Delayed puberty in uremia: pituitary-gonadal function during short-term pulsatile luteinizing hormone-releasing hormone administration.

Pubertal development is frequently delayed or disordered in children with chronic renal failure. Both neuroendocrine and peripheral alterations due to uremia have been hypothesized to explain the impairment in the pituitary gonadal axis. The aim of the present study was to evaluate quantitative (immunological) and qualitative (biological) LH secretion, as well as FSH and sex steroids, before and during 7 days of sc LHRH administration (136-150 ng/kg bw every 120 min) in 5 uremic children (13.1-14.8 yr) with delayed puberty. Six nonuremic children (13.2-17.8 yr) with delayed puberty underwent the same schedule and served as control group. On day 0 mean immunoreactive LH (I-LH) levels were higher in uremic (4.5 +/- 0.9 mIU/ml) than in nonuremic (1.9 +/- 03 mIU/ml; p < 0.05) subjects while no differences were observed in bioactive LH (B-LH) levels (2.9 +/- 0.7 mIU/ml vs 2.4 +/- 0.3 mIU/ml). In both groups of subjects testosterone was at prepubertal levels. Spontaneous I-LH and B-LH pulses were observed sporadically in both uremic and nonuremic subjects. Short-term pulsatile LHRH administration induced significant increases in B-LH, I-LH, FSH and testosterone. The B/I LH ratio increased from day 0 (0.7 +/- 0.2) to day 7 (1.3 +/- 0.4; p < 0.05) in uremics while it showed wide fluctuations in nonuremic subjects. On day 7, 4 uremic and 5 nonuremic subjects showed a pulsatile release of B-LH after exogenous LHRH pulses. Our data document that in uremia there are qualitative as well as quantitative abnormalities in pituitary gonadal secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Restoration of the gonadotrophin response to LH-RH and oestrogen administration in patients after molar abortion.

The relation of the hypothalamic-pituitary effect on gonadotrophin secretion and the concentration of serum hCG after molar abortion was investigated. Gonadotrophin release after a bolus injection of LH-RH or conjugated oestrogens was observed in 17 women until 5 months after molar abortion. Little if any response of gonadotrophin was observed at a hCG level of 100 mIU/ml or more, but the response of LH and FSH to LH-RH were restored to normal when the serum hCG level decreased to below 100 mIU/ml. A normal response of LH to conjugated oestrogens was observed at a serum hCG level of 20 mIU/ml or less. These findings suggest that a high level of hCG interferes with pituitary gonadotrophin secretion, that the threshold hCG levels for normal responses of gonadotrophins to LH-RH and oestrogen are 100 and 20 mIU/ml, respectively, and that secretion of gonadotrophins is restored even in the presence of a low hCG level.     

Clomiphene citrate induces pituitary GnRH receptors in ovariectomized rats: its possible role in induction of ovulation

Since our previous studies have shown that clomiphene citrate (clomiphene) acts directly on the pituitary gland and exerts a facilitatory role on oestradiol-17 beta (E2)-induced LH surge in chronically ovariectomized rats, the effect of clomiphene on pituitary GnRH receptors was investigated. A single ip injection of either 5 micrograms E2 or 200 micrograms clomiphene did not induce LH release in adult rats ovariectomized 1-2 weeks before the injection. However, a significant increase in serum LH was noted 24 h after a single injection of E2 in the ovariectomized rats, if clomiphene was pre-injected 48 h before the E2 injection. The content of pituitary GnRH receptors in the ovariectomized rats (62 +/- 9 fmol/pituitary) remained almost unchanged until 24 h after a single injection of clomiphene but significantly increased 48 h after the injection (105 +/- 13 fmol/pituitary) without any alterations in the affinity for GnRH. To determine steroid specificity for the increase in pituitary GnRH receptors, other classes of steroids were injected in the ovariectomized rats. A single dose of E2 increased GnRH receptors, but either progesterone or 5 alpha-dihydrotestosterone failed to show any effect on the level of GnRH receptors. These results suggest that clomiphene may augment oestrogen-induced pre-ovulatory LH surge in anovulatory women, at least in part by increasing the number of pituitary GnRH receptors.     

The effects of bromocriptine on anovulatory patients with high LH and euprolactinemia

It is well known that an acute administration of Bromocriptine (dopamine agonist) suppresses the serum LH level either in normal women or in women with polycystic ovary syndrome, in whom the serum LH level is elevated. The present study was carried out to examine the effectiveness of Bromocriptine on anovulatory women with a high LH level (serum LH greater than 30 mIU/ml). Bromocriptine was administered for 3 months, 5 mg daily, to 9 anovulatory women with euprolactinemia (serum PRL less than 25 ng/ml). Ovulation was observed by their BBT charts. Before and after the treatment of Bromocriptine, FSH, LH and PRL secreting capacities were tested by LHRH and TRH injection. Also, estrone, estradiol and testosterone levels were measured before and after the Bromocriptine administration. Resting levels of LH, FSH and PRL were 45.4 +/- 11.0 mIU/ml, 11.4 +/- 3.0 mIU/ml, and 14.3 +/- 4.7 ng/ml (M +/- SD), respectively, before the treatment. As a result of the treatment, the LH level was markedly decreased to 27.3 +/- 14.5 (M +/- SD, P less than 0.05), and PRL decreased to 3.76 +/- 4.2 ng/ml (M +/- SD, P less than 0.005). On the other hand, FSH did not show a marked change. The responsiveness of LH to LHRH before the treatment showed a marked increase, which was suppressed by Bromocriptine. However, FSH showed no change. The responsiveness of PRL to TRH was suppressed by Bromocriptine. Serum estrone, estradiol and testosterone levels before the treatment were 115.5 +/- 76.7 pg/ml, 93.7 +/- 61.0 pg/ml and 0.809 +/- 0.209 ng/ml (M +/- SD), respectively, which showed no significant change after the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypogonadotropic hypogonadism in idiopathic hemochromatosis: evidence for combined hypothalamic and pituitary involvement

Hypogonadism is a common finding in idiopathic hemochromatosis. Most studies have localized the defect to either the pituitary gland or the testes. We describe a case with evidence that favors the likely concomitant involvement of the hypothalamus as a factor in the observed hypogonadism. A clinically hypogonadal male with hemochromatosis had a low testosterone concentration with inappropriately normal serum LH levels. Leydig cell function was intact, as demonstrated by a normal increase in serum testosterone following HCG administration. However, although the pituitary secretion of LH was normal in response to GnRH stimulation, clomiphene administration did not produce an increase in LH and FSH, suggesting that there was a defect in the hypothalamic GnRH response. Since the FSH and prolactin responses to stimulatory testing were inadequate, coexisting pituitary dysfunction was likely also present. We conclude that this man had hypogonadism with laboratory evidence for a combined defect in hypothalamic and pituitary function.     

Bioassay of circulating luteinizing hormone in the rhesus monkey: comparison with radioimmunoassay during physiological changes.

The concentration of biologically active LH in rhesus monkey (Macaca mulatta) serum was measured by a highly sensitive bioassay based upon testosterone production by dispersed rat interstitial cells. The sensitivity of the in vitro bioassay was equal to or higher than that of radioimmunoassay, with detection limits of 0.1 mIU of human menopausal gonadotropin (hMG) or 10 ng of a rhesus pituitary gonadotropin preparation (LER-1909-2). Parallel dose-response curves were obtained for hMG and rhesus monkey pituitary gonadotropin. The method permits bioassy of LH in 20-100 micronl of serum from adult male monkeys, and from female monkeys during the follicular and luteal phases of the menstrual cycle. Bioactive LH concentrations could be assayed in 0.25 to 5 micronl of serum from mid-cycle, postmenopausal, and castrated female monkeys. Serum LH was undetectable in two hypophysectomized adult female monkeys and six intact immature animals, and was 13+/-6 (SD) mIU/ml in adult male monkeys. In adult females, follicular phase LH levels ranged from 17 to 169 mIU/ml, with a mean of 76+/-52 mIU/ml. The midcycle LH peak was 1738+/-742 mIU/ml and the luteal phase values ranged from 6-47 mIU/ml, with a mean of 35+/-5 mIU/ml. Serum LH concentrations ranged from 100 to 900 mIU/ml in two menopausal females, and from 590-1480 mIU/ml in castrated females. Treatment of castrated female monkeys with estrogen plus progesterone produced an initial two-fold rise in serum LH within 3 days, followed by a gradual decline to one-fourth to one-tenth of the initial levels after 10 days of treatment. Serum LH was suppressed to undetectable levels during the third week, and remained so for the duration of the 60-day treatment period. Bioactive serum LH levels were comparable to levels determined by radioimmunoassay during the follicular and luteal phases of the menstrual cycle, with increased bio-immunoratio at the midcycle peak. The concentrations of biologically active serum LH in rhesus monkeys were similar to those in the human female during the follicular and luteal phases of the menstrual cycle, and were higher at midcycle and after castration. Serum LH levels measured by the interstitial cell bioassay in the rhesus monkey showed appropriate physiological changes and responses to gonadal steroid administration. Furthermore, the bioassay did not detect the LH-like material measured by heterologous radioimmunoassay in the serum of hypophysectomized, immature and steroid-suppressed monkeys. Thus, the rat interstitial cell assay provides a sensitive and valid procedure for measurement of biologically active LH in the serum of these non-human primates.