Changes in circulating levels of immunoreactive follicle stimulating hormone, luteinizing hormone, and testosterone during sexual development in the rhesus monkey, Macaca mulatta

Basal serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) and the responsiveness of these hormones to a challenge dose of luteinizing hormone releasing hormone (LHRH), were determined in juvenile, pubertal, and adult rhesus monkeys. The monkey gonadotrophins were analyzed using RIA reagents supplied by the World Health Organization (WHO) Special Programme of Human Reproduction. The FSH levels which were near the assay sensitivity in immature monkeys (2.4 +/- 0.8 ng/ml) showed a discernible increase in pubertal animals (6.4 +/- 1.8 ng/ml). Compared to other two age groups, the serum FSH concentration was markedly higher (16.1 +/- 1.8 ng/ml) in adults. Serum LH levels were below the detectable limits of the assay in juvenile monkeys but rose to 16.2 +/- 3.1 ng/ml in pubertal animals. When compared to pubertal animals, a two-fold increase in LH levels paralleled changes in serum LH during the three developmental stages. Response of serum gonadotrophins and T levels to a challenge dose of LHRH (2.5 micrograms; i.v.) was variable in the different age groups. The present data suggest: an asynchronous rise of FSH and LH during the pubertal period and a temporal correlation between the testicular size and FSH concentrations; the challenge dose of LHRH, which induces a significant rise in serum LH and T levels, fails to elicit an FSH response in all the three age groups; and the pubertal as compared to adult monkeys release significantly larger quantities of LH in response to exogenous LHRH.     

Selective release of follicle-stimulating hormone by 5 alpha-dihydroprogesterone in immature ovariectomized estrogen-primed rats

The effect of 5 alpha-dihydroprogesterone (5 alpha-DHP) on gonadotropin release was examined in the immature acutely ovariectomized (OVX) rat primed with a low dose of estradiol (E2). Treatment with various doses of 5 alpha-DHP given in combination with E2 increased levels of follicle-stimulating hormone (FSH) but had no effect on serum luteinizing hormone (LH). A single injection of a maximally stimulating dose of 5 alpha-DHP (0.4 mg/kg) stimulated increases in serum FSH at 1200 h and, 6 h later, at 1800 h. Pituitary LH and FSH content was dramatically enhanced by 1600 h and levels remained elevated at 1800 h. The administration of pentobarbital at 1200 h, versus 1400 h or 1600 h, prevented the increase in basal serum FSH levels at 1800 h, implying that the release of hypothalamic LH releasing hormone (LHRH) is modulated by 5 alpha-DHP. In addition, changes in pituitary sensitivity to LHRH as a result of 5 alpha-DHP were measured and a significant increase in the magnitude of FSH release was observed at 1200 h and 1800 h. Although the LH response to LHRH in 5 alpha-DHP-treated rats was not different from controls, the duration of LH release was lengthened. These results suggest that 5 alpha-DHP may stimulate FSH release by a direct action at the pituitary level. Together, these observations support the theory that 5 alpha-DHP mediates the facilitative effect of progesterone on FSH secretion and further suggests an action of 5 alpha-DHP in this phenomenon at both pituitary and hypothalamic sites.     

A possible role for cyclic GMP in mediating the effect of luteinizing hormone releasing hormone on gonadotropin release in dispersed pituitary cells of the female rat.

In continuing studies on cyclic nucleotide involvement in the regulation of gonadotropin release, we have measured the cyclic nucleotide content and rate of LH and FSH release during stimulation by LHRH of dispersed overnight cultured cells from the pituitaries of adult female rats. The minimal effective concentration of LHRH was 0.1 nM and half maximal stimulation of gonadotropin release was observed in the presence of 1.0 nM LHRH. Significant release of both LH and FSH was detectable after only 10 min in the presence of 5 nM LHRH. The presence of fetal calf serum (FCS) in the overnight culture medium increased basal cGMP levels significantly, whereas horse serum (HS) had no effect, therefore all experiments were conducted on cells cultured in the presence of HS. Treatment of the cultured cells with the phosphodiesterase inhibitors theophylline (TH) or isobutyl-methyl-xanthine (MIX) revealed a preferential stimulatory effect of TH on basal cAMP levels and of MIX on cGMP levels. Throughout these experiments, LHRH had no effect on cAMP levels. In the presence of MIX, concentrations of the releasing hormone as low as 1 nM induced a significant rise in the level of cGMP whereas in its absence, cGMP levels appeared to be unchanged by LHRH. The increase was detectable after 10 min of incubation. MIX alone slightly increased LH and FSH release and significantly potentiated the response of the cells to increasing doses of LHRH up to, but not beyond, 10 nM. The data support the possibility that cGMP may be involved in the mechanism of action of LHRH.     

Effects of luteinizing hormone releasing hormone on gonadotrophins in the hamster

The changes in serum gonadotrophins in male hamsters following one injection of 15 μg luteinizing hormone releasing hormone (LHRH) (Group A) were compared with those following the last injection of LHRH in animals receiving an injection approximately every 12 hr for 4 days (Group B) or 12 days (Group C). Peak follicle stimulating hormone (FSH) levels (ng/ml) were 1776±218 (Group A), 2904±346 (Group B), and 4336±449 (Group C). Peak luteinizing hormone (LH) values (ng/ml) were 1352±80 (Group A), 410±12 (Group B), and 498±53 (Group C). Serum FSH:LH ratios, calculated from the concentrations measured 16 hr after the last LHRH injections, were higher in Groups B and C than in Group A. Similar injections of LHRH (100 ng or 15 μg/injection) for 6 days elevated the serum FSH:LH ratio in intact males. Five such LHRH injections (100 ng/injection) blunted the rise in serum LH in orchidectomized hamsters. Direct effects of LHRH on gonadotrophin secretory dynamics or altered brain-pituitary-testicular interactions may alter the ratio of FSH to LH in the hamster.     

Alterations in hypothalamic content of luteinizing hormone-releasing hormone associated with pineal-mediated testicular regression in the golden hamster

The adult male golden hamster will undergo testicular regression when exposed to a short photoperiod, blinding, or late afternoon injections of melatonin. The present study was conducted to compare the effects of all three treatments on serum gonadotropin levels and testicular weights, and to evaluate the effects of these treatments on hypothalamic content of both immunoreactive and bioactive luteinizing hormone-releasing hormone (LHRH) levels. Hamsters were blinded (BL), exposed to a short photoperiod (SP), or received daily injections of melatonin (MEL) for 15 wk. Each treatment (BL, SP, MEL) induced a temporally similar decline in serum luteinizing hormone (LH), serum follicle-stimulating hormone (FSH), and testicular weight. Spontaneous recrudescence occurred earliest in the MEL group, with serum gonadotropins and testicular weight returning to normal by 15 wk. The SP group exhibited recovery of serum gonadotropins but not testicular weight by 15 wk. The BL group demonstrated partial recovery of serum FSH levels by 15 wk, with no recovery in either serum LH or testicular weight. Each treatment group demonstrated increased hypothalamic content of immunoreactive LHRH which was temporally correlated with the decreases of serum gonadotropins. Additionally, the MEL and SP groups demonstrated decreased immunoreactive LHRH levels during spontaneous recrudescence. Extracts of hypothalami from all treatment groups were bioactive on control hamster pituitary cells. These results indicate that there are temporal differences among the three common treatments and that these differences are manifested in serum gonadotropins, testicular weight and hypothalamic LHRH. Hypothalamic LHRH levels determined by radioimmunoassay and bioassay show periods of increase and decrease which coincide with periods of altered serum gonadotropin levels in all groups.     

Possible negative ultra-short loop feedback of luteinizing hormone releasing hormone (LHRH) in the ovariectomized rat

To determine if LHRH might act within the brain to modify its own release, repeated blood samples were removed from conscious ovariectomized rats and minute doses of LHRH were injected into the third ventricle (3V). The effect of these injections on plasma LH and FSH was measured by radioimmunoassay (RIA). The higher dose of intraventricular LHRH (10 ng in 2 microliter) induced an increase in plasma LH within 10 min after its injection. Plasma LH decreased for the next 60 min. This was followed by restoration of LH pulses characteristic of the ovariectomized rat. This dose of LHRH slightly elevated plasma FSH concentrations. In stark contrast, a 10 fold lower dose of 1 ng of LHRH injected into the ventricle resulted in a highly significant decrease of plasma LH at 10 min following injection, followed by return of LH pulsations. There was no effect on the pulsatile release of FSH. The results are interpreted to mean that at the higher dose, sufficient LHRH reached the site of origin of the hypophyseal portal vessels in the median eminence so that it diffused into portal vessels and was delivered to the gonadotrophs to induce LH release. In contrast, the lower dose provided sufficient hypothalamic concentrations of the peptide to suppress the discharge of the LHRH neurons, thereby leading to a decline in plasma LH, indicative of an ultrashort-loop negative feedback of LHRH to suppress its own release.     

Detrimental effects of short-term ethanol exposure on reproductive function in the female rat

To more completely assess the means by which alcohol impairs the female reproductive cycle in rats, we have measured hypothalamic luteinizing hormone-releasing hormone (LHRH), pituitary LHRH receptor content, and the serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (Prl), and progesterone (P). After two successive cycles, the animals began receiving either an alcohol or a isocaloric control liquid diet regimen beginning on the first day of diestrus, with continued monitoring of the estrous cycle throughout the experiment. An additional set of controls consisted of animals maintained on lab chow and water provided ad libitum. Our results indicate that those animals receiving the control diets showed uninterrupted estrous patterns, whereas those animals receiving the alcohol diet remained in diestrus. Additionally, the alcohol-treated animals showed an increase (p less than 0.05) in LHRH content, with a concomitant decrease (p less than 0.01) in serum LH, and an increase (p less than 0.01) in serum Prl. No significant differences were detected in serum FSH levels or pituitary LHRH receptor content. No differences were detected in serum P levels. These results indicate that short-term alcohol administration disrupts the female reproductive cycle, causing persistent diestrus, and support our hypothesis that the alcohol-induced depression in serum LH levels is due to a diminished release rate of hypothalamic LHRH.     

Median eminence lesions reveal separate hypothalamic control of pulsatile follicle-stimulating hormone and luteinizing hormone release

The effects of hypothalamic lesions designed to destroy either the anterior median eminence (ME) or the posterior and mid-ME on pulsatile release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were determined in castrated male rats. In sham-operated animals, mean plasma FSH concentrations rose to peak at 10 min after the onset of sampling, whereas LH declined to a nadir during this time. In the final sample at 120 min, the mean FSH concentrations peaked as LH decreased to its minimal value. In rats with anterior ME lesions, there was suppression of LH pulses with continuing FSH pulses in 12 of 21 rats. On the other hand, in animals with posterior to mid-ME lesions, 3 out of 21 rats had elimination of FSH pulses, whereas LH pulses were maintained. Fifteen of 42 operated rats had complete ME lesions, and pulses of both hormones were abolished. The remaining 12 rats had partial ME lesions that produced a partial block of the release of both hormones. The results support the concept of separate hypothalamic control of FSH and LH release with the axons of the putative FSH-releasing factor (FSHRF) neuronal system terminating primarily in the mid- to caudal ME, whereas those of the LHRH neuronal system terminate in the anterior and mid-median eminence. We hypothesize that pulses of FSH alone are mediated by release of the FSHRF into the hypophyseal portal vessels, whereas those of LH alone are mediated by LHRH. Pulses of both gonadotropins simultaneously may be mediated by pulses of both releasing hormones simultaneously. Alternatively, relatively large pulses of LHRH alone may account for simultaneous pulses of both gonadotropins since LHRH has intrinsic FSH-releasing activity.     

Testosterone selectively increases serum follicle-stimulating hormonal (FSH) but not luteinizing hormone (LH) in gonadotropin-releasing hormone antagonist-treated male rats: evidence for differential regulation of LH and FSH secretion

Both testosterone (T) and gonadotropin-releasing hormone (GnRH)-antagonist (GnRH-A) when given alone lower serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in intact and castrated rats. However, when graded doses of testosterone enanthate (T.E.) were given to GnRH-A-treated intact male rats, a paradoxical dose-dependent increase in serum FSH occurred; whereas serum LH remained suppressed. This surprising finding led us to ask whether the paradoxical increase in serum FSH in GnRH-A-suppressed animals was a direct stimulatory effect of T on the hypothalamic-pituitary axis or the result of a T effect on a testicular regulator of FSH. To test these hypotheses, we treated adult male castrated rats with GnRH-A and graded doses of T.E. In both intact and castrated rats, serum LH remained undetectable in GnRH-A-treated rats with or without T.E. However, addition of T.E. to GnRH-A led to a dose-dependent increase in serum FSH in castrated animals as well, thus pointing against mediation by a selective testicular regulator of FSH. These data provide evidence that pituitary LH and FSH responses may be differentially regulated under certain conditions. When the action of GnRH is blocked (such as in GnRH-A-treated animals), T directly and selectively increases pituitary FSH secretion.     

Evaluation of the pituitary-testicular function during experimental nephrosis

To investigate the pituitary-testicular function in nephrotic rats, a sequence of experiments was undertaken in adult male rats after a single dose of puromycin aminonucleoside (PAN). Endocrine modifications were evaluated chronologically throughout the experimental disease in order to determine the appearance of hormone alterations which lead to the axis dysfunction. Serum concentration of LH, FSH, androstenedione, total and free testosterone, estradiol as well as urine testosterone were measured by specific RIAs on days 3, 7 and 10 after treatment on nephrotic and control groups. Prolactin was also evaluated on day 10. Likewise, total weight of various androgen responsive tissues from both groups was recorded, and the number of androgen receptor (AR) binding sites were determined. To know the functional status of the hipophyseal-testicular unit, groups of nephrotic and control rats were stimulated with LHRH (300 ng/100 g b.w.) or with one or four doses of hCG (8 UI), respectively. Additionally, the relative in vitro biological activity of FSH from nephrotic and control rats before and after LHRH stimulus was determined. The results from the hormonal profile revealed clear endocrine disorders characterized by a progressive diminution of all serum hormones except prolactin and urine testosterone, which remained unmodified. The weight of the main androgen responsive tissues, the ventral prostate and the seminal vesicle, decreased parallelly to androgen diminution. The binding analysis of AR shows a significant elevation of the available androgen sites in all analyzed tissues except kidney and hypothalamus. The secretion of LH and FSH from nephrotic animals after LHRH administration was lower than that from intact animals at the registered times. Interestingly, the biological activity of FSH from nephrotic rats was not detectable at both, before and after LHRH administration. Testicular response to hCG stimuli, in terms of testosterone synthesis was not significantly different in the two groups analyzed with respect to the intact animals. By contrast, no response was observed in terms of estradiol production at either one or four doses of hCG. On the whole, the results presented herein allow us to conclude that experimental nephrosis has a harmful effect on the pituitary-testicular axis, and strongly suggests that the endocrine dysfunction is initiated at the hypophyseal level; even though a specific testicular damage is also present.     

Effects of hypothalamic neurohormones on prolactin release from pituitary allografts in the hamster

Recent reports indicate that luteinizing hormone-releasing hormone (LHRH) releases prolactin (PRL) under some circumstances. We examined the chronic effects of LHRH, growth hormone-releasing hormone (GHRH), and corticotrophin-releasing hormone (CRH) on the release of PRL, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) by pituitary allografts in hypophysectomized, orchidectomized hamsters. Entire pituitary glands removed from 7-week-old-male Golden Syrian hamsters were placed under the renal capsule of hypophysectomized, orchidectomized 12-week-old hamsters. Beginning 6 days postgrafting, hamsters were injected subcutaneously twice daily with 1 microgram LHRH, 4 micrograms GHRH, or 4 micrograms CRH in 100 microliter of vehicle for 16 days. Six hosts from each of the four groups were decapitated on Day 17, 16 hr after the last injection. Prolactin, LH, and FSH were measured in serum collected from the trunk blood. Treatment with LHRH significantly elevated serum PRL levels above those measured in the other three groups, which were all similar to one another. Serum LH levels in hosts treated with vehicle were elevated above those measured in the other three groups. Serum FSH levels in hosts treated with LHRH were greater than FSH levels in any of the other three groups. These results indicate that chronic treatment with LHRH can stimulate PRL and FSH release by ectopic pituitary cells in the hamster.     

Modulation of pituitary responsiveness to LHRH by androgens in ovariectomized female rats.

The effect of androgens on pituitary response to luteinizing-hormore-releasing hormone (LHRH) and their ability to modify effects of 17beta-estradiol (E2) on pituitary responsiveness to LHRH were tested in ovariectomized rats maintained on a daily dose of 0.25 microgram estradiol benzoate per rat for 6 d before androgen administration. Testosterone propionate (TP) (4, 40, 400, or 4000 microgram per rat), administered 24 h before LHRH (500 ng per rat), had no significant effect on luteinizing hormone (LH) or follicle-stimulating hormone (FSH) response. Similar doses of dihydrotestosterone (DHT) did not significantly alter the LH response but significantly suppressed the FSH response. Even the lowest dose completely blocked the FSH response to LHRH. TP in combination with 4 or 400 microgram of E2 suppressed the stimulatory effect of E2 on both LH and FSH response to LHRH in a dose-related manner. DHT and E2 in combination affected LH response inconsistently, whereas their ratio determined FSH response; there was pronounced inhibition of FSH response in rats given high doses of DHT combined with low doses of E2; DHT inhibition of FSH response in animals receiving 4 microgram of DHT with 400 microgram E2 was partially overcome by the stimulatory effect of E2. Our results indicate that TP and DHT affect LH and FSH response to LHRH differently. The ratio of androgen to estrogen is important in determining the response to LHRH.     

Delay in the age of balano-preputial skinfold cleavage and alterations in serum profiles of testosterone, 5 alpha-androstane-3 alpha,17 beta-diol, and gonadotropins in adult rats treated during puberty with luteinizing hormone releasing hormone

Previous work has shown that chronic treatment of intact, immature male rats with luteinizing hormone releasing hormone (LHRH) decreases sex accessory gland weights and results in retardation of the normal developmental increase in the ratio of serum testosterone (T)/5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-Diol) via an apparent enhancement of testicular 5 alpha-reductase or 3 alpha-hydroxysteroid oxidoreductase activities. In the present work, androgen dependent balano-preputial skinfold cleavage was significantly delayed by approximately one week in intact, immature male rats which were treated daily for two weeks with either 1.0 micrograms, 2.5 micrograms or 5.0 micrograms of LHRH during a discrete phase of pubertal development (28-41 days of age). In intact, adult (62 day old) animals which received LHRH treatments during pubertal development, serum T concentrations and sex accessory gland weights were reduced compared to control animal values. Serum 3 alpha-Diol content in the adult rats was either unaltered or increased significantly depending on the LHRH dosage employed during sexual development. Serum luteinizing hormone concentrations were not different between control and LHRH-pretreated adult rats whereas the highest dosage of LHRH employed (5.0 micrograms) during puberty resulted in a significant elevation of adult serum follicle stimulating hormone levels. It is suggested that chronic LHRH treatment of the male rat during puberty results in a perturbation in testicular androgen biosynthetic activities and an impairment of pituitary-testicular hormone feedback mechanisms which persist at least through early adulthood.     

Pituitary luteinizing hormone-releasing hormone receptors in ovariectomized cows after challenge with ovarian steroids

Acute changes of bovine pituitary luteinizing hormone-releasing hormone (LHRH) receptors in response to steroid challenges have not been documented. To investigate these changes 96 ovariectomized (OVX) cows were randomly allotted to one of the following treatments: 1) 1 mg estriol (E3); 2) 1 mg 17 beta-estradiol (E2); or 3) 25 mg progesterone (P) twice daily for 7 days before 1 mg E2 and continuing to the end of the experiment. Serum was collected at hourly intervals from 4 animals in each group for 28 h following estrogen treatment. Four animals from each treatment were killed at 4-h intervals from 0 to 28 h after estrogen injection to recover pituitaries and hypothalami. Treatment with E3 or E2 decreased serum luteinizing hormone (LH) within 3 h and was followed by surges of LH that were temporally and quantitatively similar (P greater than 0.05). Progesterone did not block the decline in serum LH, but did prevent (P less than 0.05) the E2-induced surge of LH. Serum follicle-stimulating hormone (FSH) was unaffected (P less than 0.05) by treatment. Pituitary concentrations of LH and FSH were maximal (P less than 0.001) at 16 h for E3 and 20 h for E2, whereas P prevented (P greater than 0.05) the pituitary gonadotropin increase. Concentrations of LHRH in the hypothalamus were similar (P greater than 0.05) among treatments. Pituitary concentrations of receptors for LHRH were maximal (P less than 0.005) 12 h after estrogen injection (approximately 8 h before the LH surge), even in the presence of P. This study demonstrated that in the OVX cow: 1) E2 and E3 increased the concentration of receptors for LHRH and this increase occurred before the surge of LH; and 2) P did not block the E2-induced increase in pituitary receptors for LHRH but did prevent the surge of LH.     

Inhibitory effects of a luteinizing-hormone-releasing hormone agonist implant on ovine fetal gonadotrophin secretion and pituitary sensitivity to luteinizing-hormone-releasing hormone.

Sheep fetuses at day 70 of gestation (term = 145 days) were implanted subcutaneously with a biodegradable implant containing a luteinizing-hormone-releasing hormone (LHRH) agonist (buserelin) to investigate whether treatment with LHRH agonist would induce a state of desensitization of the fetal gonadotrophs and thus influence fetal gonadal development. Treatment with the LHRH agonist for 35-40 days caused a significant reduction in mean fetal plasma concentrations of LH and follicle-stimulating hormone (FSH) compared with control fetuses. LH pulses were evident in control fetuses but were completely abolished by buserelin treatment. Furthermore, the pituitary content of LH and FSH was significantly depleted in fetuses implanted with LHRH agonist. A bolus intravenous injection of 500 ng LHRH given to control fetuses caused a rapid and significant increase in plasma LH and FSH concentrations which was sustained for at least 60 min after injection. Pretreatment with buserelin completely abolished the LH and FSH responses to a bolus injection of LHRH. There were no differences between the sexes in fetal gonadotrophin concentrations or pituitary sensitivity to LHRH in control or agonist-treated fetuses. Furthermore, buserelin treatment for 35-40 days had no effect on the morphological appearance of the fetal gonads when compared with control fetuses, at least to day 110 of pregnancy. These results provide evidence for the induction of a state of desensitization of the LHRH receptors of the fetal pituitary gonadotrophs following long-term treatment with an LHRH agonist, but provide no evidence for a role for gonadotrophin secretion in gonadal development at this stage in fetal life.     

Effects of intermittent pulsatile infusion of luteinizing hormone-releasing hormone on dihydrotestosterone-suppressed gonadotropin secretion in castrate rams

The feedback effects of dihydrotestosterone (DHT) on gonadotropin secretion in rams were investigated using DHT-implanted castrate rams (wethers) infused with intermittent pulsatile luteinizing hormone-releasing hormone (LHRH) for 14 days. Castration, as anticipated, reduced both serum testosterone and DHT but elevated serum LH and follicle-stimulating hormone (FSH). Dihydrotestosterone implants raised serum DHT in wethers to intact ram levels and blocked the LH and FSH response to castration. The secretory profile of these individuals failed to show an endogenous LH pulse during any of the scheduled blood sampling periods, but a small LH pulse was observed following a 5-ng/kg LHRH challenge injection. Dihydrotestosterone-implanted wethers given repeated LHRH injections beginning at the time of castration increased serum FSH and yielded LH pulses that were temporally coupled to exogenous LHRH administration. While the frequency of these secretory episodes was comparable to that observed for castrates, amplitudes of the induced LH pulses were blunted relative to those observed for similarly infused, testosterone-implanted castrates. Dihydrotestosterone was also shown to inhibit LH and FSH secretion and serum testosterone concentrations in intact rams. In summary, it appears that DHT may normally participate in feedback regulation of LH and FSH secretion in rams. These data suggest androgen feedback is regulated by deceleration of the hypothalamic LHRH pulse generator and direct actions at the level of the adenohypophysis.     

Selective release of luteinizing hormone by 3 alpha-hydroxy-5 alpha-pregnan-20-one in immature ovariectomized estrogen-primed rats

This study investigated the role of 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha,5 alpha-THP) in the modulation of gonadotropin secretion using the immature ovariectomized (OVX) rat primed with a low dose of estradiol. A treatment regimen of either 0.2 or 0.4 mg/kg of 3 alpha,5 alpha-THP given in conjunction with estradiol for 4 days significantly increased levels of serum luteinizing hormone (LH) but had no effect on serum follicle-stimulating hormone (FSH). Estrogen-primed rats receiving a single injection of 3 alpha,5 alpha-THP at 0930 h showed an increase in serum and pituitary LH levels at 1200 h and 1500 h. At 1800 h, only pituitary levels of LH remained significantly higher than controls. An injection of 3 alpha,5 alpha-THP at 1230 h in estrogen-primed rats resulted in enhanced levels of pituitary LH at 1500 h and elevated levels of both serum and pituitary LH at 1800 h. When 3 alpha,5 alpha-THP was given at 0930 h and 1230 h, elevated serum levels of LH were maintained for over 6 h. The administration of pentobarbital (Pb) 30 min after an injection of 3 alpha,5 alpha-THP at 0930 h or 1230 h prevented the increases in serum LH at 1200 h, 1500 h or 1800 h. This suggests that LH-releasing hormone (LHRH) is involved in mediating the LH response by 3 alpha,5 alpha-THP. There was no change in the sensitivity of the pituitary to LHRH following 3 alpha,5 alpha-THP treatment, indicating the absence of a pituitary effect of this steroid.     

Studies on the effects of low doses of 5 alpha-dihydrotestosterone (DHT) on the basal levels of serum gonadotropins and the sensitivity of the pituitary to luteinizing hormone releasing hormone (LHRH) in adult male rats

Investigations were undertaken to study the effect of administering s.c. 10, 25, 50, 100, 500 and 1000 ng DHT/rat/day to normal adult male rats, for six weeks, on the basal levels of serum gonadotropin and the sensitivity of the pituitary to LHRH. The control group received olive oil. Animals were weighed and bled via cardiac puncture before the beginning of the treatment and weekly thereafter. After the last bleeding rats were injected intracardially 200 ng LHRH/rat and killed 15 min later. Blood, pituitary and testes were collected. Data were analyzed with respect to the control group and with respect to day zero of the treatment. DHT failed to produce a persistent effect on the serum gonadotropin. 10 and 500 ng DHT suppressed FSH levels significantly on days 21 and 7, respectively. 25, 50, 100 and 1000 ng DHT stimulated the release of FSH on day 42. 10 ng DHT reduced the levels of LH on day 14 of the treatment. 10, 25 and 50 ng DHT increased the sensitivity of the pituitary to release more LH in response to LHRH while 100, 500, 1000 ng DHT inhibited LHRH induced release of FSH. DHT at all doses tested failed to affect intrapituitary levels of LH and FSH. 10, 500 and 1000 ng DHT reduced the weights of the pituitaries as compared to the control group. The data demonstrate effects of DHT which are transient on the basal release of gonadotropins but are more persistent and differential on the sensitivity of the pituitary to LHRH.     

A new male hypogonadism mutant rat (hgn/hgn): concentrations of testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in the serum and the responsiveness of accessory sex organs to exogenous T, FSH, human chorionic gonadotropin, and luteinizing hormone-releasing hormone

To determine the etiology of male hypogonadism in a newly found mutant rat (hgn/hgn, with a single autosomal recessive trait), concentrations of testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured, and the responsiveness of the urogenital organs, hypothalamus, and pituitary gland to testosterone (1 mg/kg s.c. for 7 days), FSH (0.3 AU/kg s.c. for 7 days), human chorionic gonadotropin (hCG) (40 IU/kg s.c. for 7 days), and luteinizing hormone-releasing hormone (LHRH) (0.5 or 5.0 micrograms/kg s.c. for 7 days) were tested. Treatment with testosterone only increased the weights of all of the accessory sex organs, whereas treatment with FSH, hCG, or LHRH did not. Levels of serum FSH and LH were extremely higher and testosterone was lower in hgn/hgn males than in normal males. Serum FSH and LH decreased to levels found in intact animals after treatment with testosterone, suggesting that hypothalamic responsiveness to exogenous testosterone is present in the hgn/hgn males. Thus, the status of the hgn/hgn males was indicated to be due to primary Leydig cell dysfunction.     

Short-term pulsatile administration of luteinizing hormone releasing hormone in male adolescents with multiple idiopathic pituitary hormone deficiencies

In order to define both level and severity of defect in patients with idiopathic multiple pituitary hormone deficiencies (MPHD) and to find out which patient might benefit from pulsatile LHRH substitution therapy, the effect of short-term pulsatile LHRH infusion in 6 affected male adolescents was studied. Controls were 9 boys with constitutional delay of puberty (CD). During a spontaneous nocturnal plasma profile LH and FSH levels were prepubertal with little evidence of pulsatile secretory LH activity in all MPHD patients. During short-term pulsatile LHRH stimulation (36 h), however, all showed a significant rise in mean LH and FSH levels (p less than 0.0001). Linear regression analysis revealed significant continuous increases of FSH (p less than 0.001) in all patients and of LH (p less than 0.01) in all but one patient. These changes were not accompanied by an increase of testosterone, androstenedione and DHAS levels. Since all MPHD patients showed steadily increasing gonadotropin levels if stimulated in a pulsatile manner, we conclude that the defect might only in part be located at the pituitary level. Long-term pulsatile substitution therapy with LHRH is likely to be successful in these patients as has been demonstrated in patients with known hypothalamic defect.