LRH Administration Research Articles

Interaction of inhibin and estrogens on basal and LRH-stimulated gonadotropin levels.

In order to study the action of estrogens and inhibin and their interaction with gonadotropin secretion in men, we measured basal and LRH-stimulated gonadotropin secretion before and after six weeks' administration of tamoxifen in two groups of men. A) Six men with impaired spermatogenesis with basal levels of FSH, LH, testosterone and estradiol within the range of reference values in our laboratory. B) Six men with severely impaired spermatogenesis. LH, testosterone and estradiol levels were within reference values, whereas FSH was at least 100% above the upper limit of reference values. Mean testosterone and estradiol levels were not different in either groups. Inhibin levels were presumed to be normal in group A and decreased in group B. Although within reference values, basal LH levels in group B were slightly but significantly higher than in group A. The response of LH to LRH in group B exceeded that of group A. This suggests that inhibin has a slightly inhibitory effect on basal LH and even more so on LRH-induced LH secretion. After tamoxifen administration basal FSH levels rose far more in group B than in group A. The LRH-induced LH release increased in both groups, the LRH-stimulated FSH release, however, increased only in group A. We conclude that estrogens and inhibin have a strongly synergistic negative feedback action on basal FSH secretion, and to a limited extent on basal LH secretion. In the presumed presence of inhibin (group A) the FSH additionally synthesized through the action of anti-estrogens, can be released by LRH administration, whereas FSH is probably spontaneously released in the presumed deficiency of inhibin (group B). With LH this phenomenon is less obvious.

Abnormal beta-endorphin and beta-lipotropin responses to TRH and LRH administration in primary and secondary affective disorders.

Anomalous anterior pituitary hormone responses to acute administration of TRH and LRH have previously been observed in patients with primary affective disorders (PAD), with TRH eliciting GH, FSH and LH rises, and LRH eliciting GH and Prl rises. We examined whether the same unusual responses were present also for beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) in 15 PAD patients, in 9 patients with secondary affective disorders (SAD), and in 7 controls. TRH (500 micrograms iv) elicited rises of beta-EP plasma levels in 5 PAD and 2 SAD patients, and of beta-LPH in 4 PAD and 3 SAD patients. LRH (150 micrograms iv) elicited rises of plasma beta-EP levels in 2 PAD and 2 SAD patients, and of beta-LPH in 5 PAD and 2 SAD patients. No rises of beta-EP and beta-LPH plasma levels were observed in PAD patients after saline administration, nor in the controls after TRH, LRH or saline administration.

LRH administration in increasing frequency schedules in the hypogonadotropic male patient

In search for an optimal induction of puberty, LRH was administered iv in three different consecutive schedules, each lasting for 4 weeks in three hypogonadotropic boys: Results: Schedule 1 elicited a clear increase of the FSH level, while LH and T (Testosterone) increased slightly. On the presumed physiologic schedule 2 (Santen and Bardin, 1973) LH, FSH and T increased into the normal adult range.Only 1 patient showed LH pulses strictly coincident with the exogenous LRH pulses. On schedule 3 gonadotropin and T levels remained high or even further increased. There was no evidence of desensitization of the gonadotrophic cells. These data suggest that: 1. The increase of gonadotropins during early puberty (FSH first, followed by LH) may be the result of increasing LRH stimulation with a pulse frequency lower than presumed physiologic in adults. 2. Pulsatile LRH treatment with a frequency higher than "physiologic" does not result necessarily in desensitization of the gonadotrophic cells, in contrast to observations in the female rhesus monkey (Wildt et al., 1981).

Hypothalamic function in women during the first month post-partum.

Plasma LRH-immunoreactive substance in puerperal women was very low on days 5 and 10 post-partum and significantly increased between days 10 and 20 post-partum, but remained at a similar level on day 30 post-partum, which was significantly lower than that in eumenorrhoeic women on day 8 or 9 of the normal cycle. Although LRH administration did not significantly increase serum FSH on day 11 post-partum, daily injections of LRH from days 5 through 10 post-partum caused a significantly increased secretion of FSH on day 11 post-partum, both basally and in response to LRH. No significant difference was observed in serum oestradiol and Prl levels on day 11 post-partum between the two groups of women with and without LRH pre-treatment. It is concluded that the amount of hypothalamic LRH secretion may be small during the first month post-partum, and low basal FSH and unresponsiveness of the pituitary to LRH observed in the early puerperium may result from hypothalamic hypofunction.

Starvation induced anoestrus: effect of chronic food restriction on body weight, its influence on oestrous cycle and gonadotrophin secretion in rats

To test the effect of chronic starvation on gonadotrophin secretion and oestrous cycles, rats were fed 50% of their normal chow consumption for 16 days. This caused an increasing rate of anoestrus which became significant during the third expected cycle (6 of 10 rats, P less than 0.02) and increased to 8 of 10 rats (P less than 0.0001) between day 12 and 16. The accompanying weight loss was around 13 and 17%, respectively. Pituitary weights in intact rats killed on dioestrus became significantly different after 8 days of chow reduction (12.8 +/- 0.2 vs 11.3 +/- 0.4 mg, P less than 0.02) with further reductions in groups killed after 12 and 16 days. At this time dioestrous serum FSH levels were significantly increased in starved rats (112 +/- 16 vs 161 +/- 13 ng/ml, P less than 0.01), while serum LH levels decreased significantly after 12 days (25.0 +/- 3.4 vs 13.1 +/- 8.8 ng/ml, P less than 0.001). Starvation decreased the LH response to LRH administration compared to pro-oestrous controls (1934 +/- 672 vs 289 +/- 39 ng/ml, P less than 0.05), whereas the FSH response was not impaired (457 +/- 91 vs 336 +/- 54 ng/ml, P greater than 0.05). In contrast to this pituitary content of LH was similar in both groups, while FSH content was significantly higher in starved animals (13.6 +/- 1.7 vs 19.8 +/- 1.2 micrograms, P less than 0.01). Chronic starvation immediately after ovariectomy did not affect the post-castrational rise of gonadotrophins. However, LRH administration caused higher serum FSH levels in starved rats (1540 +/- 91 vs 1833 +/- 90 ng/ml, P less than 0.05), whereas LH values did not differ (908 +/- 192 vs 721 +/- 153 ng/ml, P greater than 0.05). Gonadotrophin content per pituitary in castrated rats after 16 days of starvation was unchanged.

Influence of pulsatile administration of LRH on the development of the augmentative (positive) effect of oestradiol on the pituitary response to LRH.

Ovariectomized (OVX) rats were treated for 24 h with pulses of LRH (1.25 ng/100 g b.w. every 20 min) or of saline. Moreover, the animals received 3 sc injections of oestradiol benzoate (EB) (50 micrograms) or oil during this period. At the end of this period all animals received phenobarbital (80 mg/kg ip) and the animals were given pulses of LRH (once every 20 min) containing 1.25, 2.5, 5.0 or 10 ng for 3 h. Pulsatile administration of 1.25 ng pulses for 24 h did not lead to pituitary insensitivity. Treatment with EB caused the development of an increased response to LRH (positive effect). When during the 24-27 h period 5.0 or 10.0 ng pulses of LRH were given, the positive response was the same whether LRH had been administered during the 0-24 h period or not. However, the response to 2.5 ng pulses of LRH was halved when the animals had been pre-treated with LRH. It is concluded that the presence of LRH can inhibit partly the development of the positive pituitary response to LRH as caused by EB. When the dose of LRH was kept at 1.25 ng/pulse no clear positive effect developed. Chronic administration of phenobarbital for 24 h caused pituitary insensitivity, presumably through a direct toxic effect.

The pituitary-testicular axis of uraemic subjects on haemodialysis and continuous ambulatory peritoneal dialysis.

Pituitary-testicular function was evaluated in 18 patients with chronic renal failure, 9 treated by maintenance haemodialysis (HD) and 9 by continuous ambulatory peritoneal dialysis (CAPD), and compared with a non-uraemic control group. Serum total testosterone and the free testosterone index were significantly low in both dialysis groups. Basal FSH and LH levels were elevated but this reached significance only with regard to LH. The responses of both FSH and LH to the iv administration of LRH were normal. There was no significant difference between the CAPD and HD groups in any of the hormonal parameters estimated. While CAPD may improve control of some metabolic parameters when compared with HD, it does not improve the function of the pituitary-testicular axis.

The effects of thyrotropin-releasing hormone and luteinizing hormone-releasing hormone on growth hormone release in patients with homozygous beta-thalassaemia.

Serum GH levels were measured in 12 multitrans- patients, whereas no effect was observed in the normal subjects, fused patients with β-thalassaemia and in 12 normal subjects ofcomparable age under control conditions and after the administration of synthetic TRH and synthetic LRH. TRH administration induced a paradoxical rise in GH levels in 8 out of 12 patients, whereas no effect was observed in the normal subjects. Synthetic LRH administration was devoid of any effect on serum GH in both patients and controls. (J Clin Endocrinol Metab 54:1271, 1982)

Effects of Porcine Follicular Fluid on Gonadotropin Concentrations in Rhesus Monkeys*

The administration of steroid-free charcoal-treated porcine follicular fluid to long term castrated female rhesus monkeys lowered basal serum concentrations of FSH and had almost no effect on serum LH. Treatment with porcine follicular fluid before the administration of exogenous LRH inhibited the release of FSH, but also affected the release of LH. This inhibition was especially striking on the suppression of the peak of release of both FSH or LH at 20 min. These findings suggest that an inhibin-like material present in follicular fluid could play an important role in the secretion of FSH and LH in rhesus monkeys.

Influence of LRH on gonadotrophin and testosterone levels in the foetal male rat

Gonadotrophin and testosterone levels were measured in male foetal rats at the 21st day of gestation 30 min following administration of LRH. The releasing hormone was administered by 3 different routes: subcutaneously as a single injection to the pregnant rat; subcutaneously as 12 times repeated injection to the pregnant rat from 16th-21st day of gestation; direct injection into the amniotic cavity. Three different doses of 1, 5, and 10 microgram/kg were used. The single administration to the dam was without effect. Repeated doses resulted in a significant dose-dependent elevation of mean foetal LH: 163 ng/ml in the control animals and 133,256, and 363 ng/ml in the 1, 5, and 10 microgram/kg LRH group resp. Intra animal injections significantly increased FSH and LH levels, but only those of FSH were clearly dose-dependent. A mean of 390 ng/ml in the control group was observed, with 1 microgram/kg LRH FSH was elevated to 723 ng/ml, at 5 microgram/kg to 928 and at 10 microgram/kg to 1017 ng/ml. Testosterone levels were not significantly altered. Our results demonstrate that the pituitary of foetal rats is able to respond to LRH in the same manner as adult animals.

The impact of euglycemia and hyperglycemia on stimulated pituitary hormone release in insulin-dependent diabetics.

To study the influence of different blood glucose (BG) concentrations on the release of pituitary hormones, the effect of the simultaneous iv administration of LRH (200 micrograms), TRH (400 micrograms), and arginine (30 g/30 min) upon the serum concentrations of LH, FSH, TSH, PRL, and GH was determined in six male insulin-dependent diabetics. BG concentration was clamped by feedback control and an automated glucose-controlled insulin infusion system at euglycemic (BG 4-5 mmol/liter) or hyperglycemic (BG, 14-18 mmol/liter) levels. Increments in serum concentrations of LH, FSH, TSH, and PRL were similar in the euglycemic and hyperglycemic steady states, whereas the GH response to arginine was suppressed during the hyperglycemic clamp (P less than 0.01). Omission of exogenous insulin during hyperglycemia did not modify the observed hormonal responses. Thus, the release of LH, FSH, TSH, and PRL in response to adequate acute stimuli at the pituitary level is not modulated by hyperglycemia in insulin-dependent diabetes, while arginine-induced GH release is suppressed. Since the effect of arginine on GH is most likely mediated by an action on the hypothalamus, the data suggest that elevated glucose concentrations may exert their modulatory influence on GH secretion at the hypothalamic rather than at the pituitary level.

Concomitant Secretion of Adrenocorticotropin, β-Endorphin, and γ-Melanotropin from Perfused Pituitary Tumor Cells of Cushing's Disease: Effects of Lysine Vasopressin, Rat Median Eminence Extracts, Thyrotropin-Releasing Hormone, and Luteinizing Hormone-Releasing Hormone∗

Regulation of secretion of ACTH-, beta-endorphin-, and gamma-melanotropin-like immunoreactivities (ACTH-LI, beta-EP-LI, and gamma-MSH-LI, respectively) was studied by using a perfused Sephadex column containing dispersed pituitary tumor cells obtained from three patients with Cushing's disease. Serial dilution of the perfusion medium gave lines parallel to the standard curve in each RIA for ACTH, beta-EP and gamma-MSH, suggesting that immunoreactive materials in the medium are immunologically indistinguishable from the authentic peptides. Gel exclusion chromatography of the medium revealed the existence of ACTH, beta-lipotropin (beta-LPH), beta-EP, and their possible precursor protein. gamma-MSH-LI consists of a major peak of big gamma-MSH eluted near the elution position of beta-LPH, suggesting the entire or nearly entire N-terminal portion of the precursor molecule. The addition of lysine vasopressin and rat median eminence extracts (MEE) to the perfusion system concomitantly enhanced the release of ACTH-LI, beta-EP-LI, and gamma-MSH-LI, although the dose-response relationship was clear-cut only in the case of MEE. TRH and LRH also elicited the concomitant release of these peptides in one patient, in whom combined administration of TRH and LRH significantly augmented plasma cortisol levels when studied preoperatively. The molar ratio of ACTH-LI to beta-EP-LI was approximately 1.0, whereas gamma-MSH-LI was about one fourth of ACTH-LI when compared on a weight basis. These results indicate that 1) ACTH-producing human pituitary adenomas concomitantly secrete ACTH, beta-LPH, beta-EP, and big gamma-MSH, and 2) lysine vasopressin, MEE, TRH, and LRH act directly on pituitary cells to stimulate the release of these peptides.

Effects of luteinizing hormone-releasing hormone on sexual arousal in normal men

Six normal adult male subjects were administered either luteinizing hormone-releasing hormone (LRH, 500 micrograms, intramuscularly injected) or a saline placebo 10 min before a 40-min laboratory session in which they were exposed to erotic stimuli; subjects attended four such sessions, twice receiving LRH and twice the placebo in a balanced, double-blind, crossover design. Sexual arousal was inferred from degree of tumescence, with penile circumference measured by a mercury-in-rubber strain gauge. Heart rate was monitored continuously, and blood samples were taken periodically and assayed for serum luteinizing hormone (LH), follicle stimulating hormone (FSH), and testosterone (T). Rapidity of onset of erection, maximum degree of erection obtained, and overall levels of tumescence were consistently greater following LRH administration than following saline placebo; however, the differences were not statistically significant. The anticipated LH and FSH response to LRH was noted as well as a small increment in LH levels following erotic stimulation. No significant alteration in serum testosterone was observed within the time sampled. There were no significant correlations between hormonal data and any measurement of penile tumescence. In view of the results, further investigation of the behavioral effects of LRH appears justified.

Plasma cortisol response to thyrotropin-releasing hormone and luteinizing hormone-releasing hormone in Cushing's disease.

In 3 of 6 patients with pituitary-dependent Cushing's disease, a paradoxical increase of plasma cortisol was observed both after LRH (delta max, 13.9 +/- 3.7 microgram/100 ml; 113 +/- 52%) and TRH (delta max, 8.0 +/- 2.9 microgram/100 ml; 53 +/- 18%) administration, the maximum values being achieved 30--60 min after the iv bolus injection. In the remaining 3 patients and in 15 control subjects, plasma cortisol levels did not rise in response to either LRH or TRH administration but rather showed a slight to distinct decrease during the study period. The paradoxical cortisol response in half of the patients with Cushing's disease may be the consequence of loss of specificity of the pituitary receptor or alteration in the hypothalamo-pituitary pathways.

Studies on the Role of Sex Steroids in the Feedback Control of Gonadotropin Concentrations in Men. III. Androgen Resistance in Primary Gonadal Failure

The negative feedback control of serum gonadotropins by sex steroids was studied in eight men with Leydig cell insufficiency, four of whom had diminished and four with unmeasurable Leydig cell function. Mean serum LH and FSH concentrations, the pattern of LH pulsatile release, and the response of gonadotropins to LRH stimulation were studied before and at the completion of 4-day continuous infusions of testosterone (T; 15 mg/day), 17/S-estradiol (E; 90 μg/day), and 5a-dihydrotestosterone (DHT; 7.0 mg/day). Both T and E infusion resulted in approximately 30% suppression of mean serum LH and FSH concentrations in hypogonadal subjects; these responses were similar to those of normal men. Neither T nor E infusion produced a decrease in LH pulse frequency or amplitude in hypogonadal men. This differs from the decrease in LH pulse frequency seen with T and the fall in LH pulse amplitude during E infusion previously observed in normal men. The fall in mean serum LH concentration during infusion of the nonaromatizable androgen DHT was significantly less in the hypogonadal (11 ± 2.7%) than in the normal men (35 ± 10%; P > 0.05). DHT resulted in an augmentation of the LH response to LRH administration in normal men, which was not observed in the hypogonadal men. No significant FSH suppression by DHT was seen in either group. The data indicate that the modulation of LH by sex steroids in men with primary hypogonadism appears to differ from normal in that there is a resistance to the effects of pure androgen. The mechanism for this resistance remains to be determined. (J Clin Endocrinol Metab48: 553, 1979)

Studies on the Role of Sex Steroids in the Feedback Control of Gonadotropin Concentrations in Men. II. Use of the Estrogen Antagonist, Clomiphene Citrate*

Abstract To further evaluate the relative roles for androgen and estrogen in the feedback regulation of gonadotropin secretion in men, we studied the effects of sex steroids on serum LH and FSH concentrations, the pulsatile release of LH, and the responses of LH and FSH to LRH administration before and during chronic clomiphene administration. We theorized that this approach might provide an opportunity to evaluate the pure androgenic component of testosterone, independent of its aromatization to estradiol, since the estrogen antagonist, clomiphene, would block estrogen-mediated effects. Infusion of testosterone (T; 7.5 mg/day for 4 days) produced a 40% decline in serum LH and FSH concentrations. Estradiol (E) infusion in dosages equivalent to that derived from the infused T (45 μg/day) resulted in a decline in serum LH which was 60% of that seen with T, indicating that most of the Tmediated LH suppression could be attributed to its aromatization to E. Dihydrotestosterone infusion also resulted in a 35% d...

The effect of prednisolone and metyrapone on FSH release induced by the administration of LRH.

The response of follicle-stimulating hormone (FSH) to a single injection of synthetic LRH was established in 7 and 6 women following an intramuscular dose of 0.2 mg and 0.1 mg. The secretion of FSH was greater in the group injected with 0.2 mg LRH than in the group injected with 0.1 mg. On the other hand, the response of FSH to a single injection of LRH (0.1 mg/subject) was established in 7 men before and after the pretreatment with metyrapone for one dat (4.5 g/subject). Pretreatment with metyrapone provoked a hypersecretion of FSH following a single injection of synthetic LRH. Seven women, 21--48 years of age who were treated with prednisolone for at least 1.5 months were examined for the responsiveness of the anterior pituitary to a single injection of synthetic LRH (0.2 MG). The secretion of FSH was not suppressed and the maximal serum level of FSH was observed 60 min after LRH injection.

Secretory cycle of the pituitary basophils and its morphological evidence.

The pituitary basophils of rats were examined electronmicroscopically at various time courses of the following experiments: Acute, subacute and chronic administration or perfusion of TRH and LRH separately or in combination to normal male and ovariectomized female rats as well as thyroidectomy on male rats. The findings showed a sequential, ultrastructural transformation (type I to V) of the basophil which might perform its secretory cycle. The I-type cells represent immature basophils. The II-type cells (correspond to classical TSH-cells) are angular cells in a synthesizing and/or storing phase showing an abundance of secretory granules 100-150nm in diameter. The II/III-type cells come into two categories of cell type, presenting a peripheral vesiculation of the cytoplasm. The III-type cells (correspond to classical LH-cells) are round in shape and possess a number of vesicular structures and secretory granules of about 200nm in diameter throughout the cell body. The III/IV-type cells are characterized by numerous round large cisternae which are filled with fine granulated particles. Secretory granules in these cells are 200-250nm in diameter. The enlarged spherical IV-type cells (correspond to classical FSH-cells) are packed with irregularly expanded endoplasmic reticula. Secretory granules are about 250nm in size. The IV-type cells are presumably at the end stage of granular storage or at the initiation of granular secretion, since there is a transitional cell type (IV/II-type) in which secretory granules are reduced in size (100-150 nm in diameter) and in electron density. Vesicular endoplasmic reticula are infrequently found in the IV/II-type cells, which may be either at the end of the secreting phase or at the subsequent resting phase. The V-type cells appear even in the normal and numerously after repeated or prolonged administrations of TRH or LRH. They may be exhausted basophils. It was not, however, concluded that II-, III-and IVtype cells might correspond to TSH-, LH-and FSH-cells, respectively.Based on a sequential appearance of the cells mentioned above, we propose a hypothesis: The II-type may transform into the III-type, and subsequently into the IV-type which may come back to the II-type.

Pituitary hormone levels in plasma of the human fetus after administration of LRH.

The concentrations of hFSH, hLH/hCG, hGH, and hTSH1 were measured in maternal and fetal blood during the second trimester of pregnancy before and after the administration of 10 mug LRH to 9 fetuses. A comparison was performed with 9 control fetuses not receiving LRH. The initial value of hFSH was significantly higher in female than in male fetuses (P less than 0.01) and in both sexes exceeded the low maternal hFSH level. A similar fetomaternal difference existed also for plasma hGH, in contrast to plasma hLH/hCG, which concentration was higher in maternal than in fetal blood LRH did not cause any change of circulating hFSH, hLH/hCG, and hTSH levels in the fetus 10 min after its administration. A rise of fetal hGH levels occurred during the observation time irrespective of LRH administration. In amniotic fluid, the hFSH concentration accorded with that in fetal blood, and the hLH/hCG concentration with that in maternal blood. The fetal plasma levels of these pituitary hormones suggest selective release mechanisms for the various peptides. The causes of the absent response of blood gonadotropin levels to LRH in the fetus are discussed.

Effect of clomiphene on basal and LRH-induced gonadotropin secretion in postmenopausal women.

LRH tests were performed in 11 postmenopausal women before and after the administration of 200 mg of clomiphene citrate daily by mouth for 7 consecutive days. The basal levels and the maximum increments of serum LH (deltaLH) and the area under the response curve from basal level (deltaarea) after LRH administration, significantly (P less than 0.005) decreased after consecutive administration of this compound. Serum FSH levels were significantly (P less than 0.025) decreased but deltaFSH and deltaarea in LRH test were statistically unchanged. These results suggest that clomiphene citrate in postmenopausal women inhibits the pituitary gonadotropin response to exogenous LRH by its estrogenic effects.