Age-related changes in the secretory pattern of FSH and LH in response to LH-RH in prepubertal female rats

Developmental changes in the pituitary responsiveness and the secretory pattern of FSH and LH in response to a single injection of LH-RH (100 ng/rat, s.c.) as estimated by increases in plasma concentrations of FSH and LH 10, 30 and 60 min after the injection were studied in female rats at 5, 10, 15, 20, 25 and 30 days of age. The pituitary responsiveness to LH-RH for both FSH and LH release increased from 5 to 15 days of age, reached a maximum on 15 days of age and declined thereafter, whereas a marked increase in the amount of these hormones in the pituitary occurred between 15 and 20 days of age. An apparent change in the secretory pattern of both FSH and LH was observed from 20 days of age onward. In groups up to 15 days of age, plasma concentrations of FSH and LH remained elevated 60 min after the injection of LH-RH, though the plasma concentration of these hormones returned to preinjection concentrations in groups at 20 days of age or later. These results indicate that the age-related changes in the secretory pattern of LH and FSH in response to LH-RH as well as changes in the pituitary responsiveness were apparent during the prepubertal period.     

Effect of neonatal testosterone and oestradiol treatment on the development of the hypothalamo-hypophysial axis in the female rat.

The hypothalamic LH-RH content and the concentrations of pituitary and plasma LH were measured at various ages in female rats treated daily with 10 micrograms testosterone propionate or 10 micrograms oestradiol-17beta from birth to Day 15. Persistent vaginal oestrus was induced in all the treated rats. Both hormones significantly reduced the hypothalamic LH-RH content and pituitary and plasma LH concentrations. Hypothalamic LH-RH increased after cessation of treatment but pituitary LH did not return to normal levels. Plasma LH levels were significantly lower than those in control rats. It is concluded that testosterone propionate and oestradiol-17beta (1) have a direct negative feed-back influence on the hypothalamus in the neonatal female rat; (2) alter the normal pattern of plasma and pituitary LH in developing female rats; (3) prevent the cyclic secretion of plasma LH after maturity; and (4) probably cause a chronic impairment in the release of LH-RH.     

Blockade of pulsatile LH, FSH and testosterone secretion in rams by constant infusion of an LHRH agonist

Adult Soay rams were infused for 21 days with 50 micrograms buserelin/day, using s.c. implanted osmotic mini-pumps. The continuous treatment with this LHRH agonist induced a supraphysiological increase in the blood concentrations of LH (15-fold) and testosterone (5-fold) followed by a decrease below pre-treatment values after 10 days. The blood concentrations of FSH showed only a minimal initial increase but the subsequent decrease was dramatic, occurring within 1 day. By Day 10 of treatment, the blood concentrations of all 3 hormones were low or declining, LH pulses were absent in the serial profiles based on 20-min blood samples and the administration of LHRH antiserum failed to affect the secretion of LH or testosterone. By Day 21, the secretion of FSH, LH and testosterone was maximally suppressed. The i.v. injection of 400 ng LHRH was totally ineffective at stimulating an increase in the blood concentrations of LH while the i.v. injection of 50 micrograms ovine LH induced a normal increase in the concentrations of testosterone; this confirmed that the chronic treatment with the LHRH agonist had desensitized the pituitary gonadotrophs without markedly affecting the responsiveness of the testicular Leydig cells. The ratio of bioactive: radioimmunoactive LH did not change during the treatment. The long-term effect of the infusion was fully reversible as shown by the increase in the blood concentrations of FSH, LH and testosterone and the return of normal pulsatile fluctuations in LH and testosterone within 7 days of the end of treatment.     

Differential effects of LH-RH immunoneutralization on LH and FSH secretion in the ewe

Neutralization of LH-RH by injection of an ovine antiserum to LH-RH in ewes during the late follicular phase of the oestrous cycle resulted in an immediate blockade of pulsatile secretion of LH. Plasma concentrations of FSH gradually rose in the antiserum-treated ewes during the 36-h study period but levels declined in control ewes. These results show that, in the ewe, pulsatile LH secretion is dependent on LH-RH from the hypothalamus, while FSH is largely unresponsive to short-term reduction of LH-RH stimulation. Since reduction in LH secretion is likely to reduce ovarian function, the changes in FSH secretion may be attributed to the removal of a negative feedback influence of an ovarian factor, perhaps oestradiol, on FSH secretion.     

Study of testicular feedback in male rats using artificial cryptorchidism as a model.

Plasma LH, FSH and testosterone were measured in testosterone-treated and untreated cryptorchid and castrated male rats. Exogenous testosterone prevented the increase in basal LH but not FSH levels seen in the untreated cryptorchids. Increases in plasma LH and FSH in response to LH-RH were greater in the cryptorchid as compared to the control group and this could not be reversed by exogenous testosterone, suggesting that spermatogenesis-related feedback factors regulate LH as well as FSH at the pituitary level in the intact rat. The results were consistent with a reduced but nevertheless significant secretion of inhibin by the cryptorchid testis. Basal plasma testosterone levels and ventral prostate weights were not significantly different from intact animals.     

Effects of an LH-RH agonist on reproductive responses and endocrinological parameters in landais ganders

Semen quantitative (sperm production) and qualitative parameters (percentage of live and normal spermatozoa, sperm motility, egg fertility and hatchability), as well as hormonal parameters (LH and testosterone plasma concentrations) were compared for landais ganders, which were treated or not, with an LH-RH agonist prior to being sexually active. Treatment with the LH-RH agonist at this physiological stage delayed the onset of sperm production in some of the treated males. Although, comparable data were obtained during the first half of the reproductive period, treatment with the LH-RH agonist maintained sperm output at higher levels during its second half. Although the percentage of normal and live spermatozoa, sperm motility and true hatchability did not differ, the LH-RH agonist treatment had a positive effect on gosling production because of the higher fertility of the treated birds during the second part of the reproductive period. Treatment induced a large short-term decrease in testosterone levels followed by a rebound, leading to higher levels during the second half of the reproductive period. We conclude that treatment of ganders with an LH-RH agonist partially prevented the naturally occurring decline in sperm production and induced an increase in the rate of fertility rates during the second half of the productive period.     

Short-term relationships between plasma LH, FSH and progesterone concentrations in post-partum dairy cows and the effect of Gn-RH injection

Jugular venous blood samples were obtained from 7 dairy cows every 10 min for 10-19 h during the early- or mid-luteal phase of the oestrous cycle, and each cow was given 1 or 2 i.v. injections of 100 micrograms synthetic Gn-RH. Four of these cows were also sampled in a different cycle with no treatment being administered. Peaks of plasma LH, FHS and progesterone were detected in each animal in the absence of treatment; those of LH and progesterone often occurred in parallel. Injection of Gn-RH was always followed by a significant increase in plasma LH and progesterone concentrations and in most cases by a significant FSH increase. There was a significant temporal relationship between the peaks of all 3 hormones. A further 8 cows were sampled during the first 10 days post partum when the mean plasma progesterone concentration was low. An i.v. injection of 200 micrograms synthetic Gn-RH was given to each animal and this resulted in a significant increase in plasma LH and FSH concentrations, but in only one cow was the Gn-RH injection followed by a significant increase in plasma progesterone concentration. The LH response to Gn-RH injection was significantly less in cows injected on or before Day 5 post partum than in cows injected on Days 7-10 post partum.     

Hypothalamic site of progesterone action on gonadotropin release

Tonic gonadotropin secretion was monitored at 20 min intervals for a total of 9 hours in 3 female volunteers during the mid-luteal phase of an ovulatory cycle. This control period was followed by repeated LH-RH stimulation (12 micrograms LH-RH as i.v. bolus once every hour for another 5 hours). During the control period spontaneous albeit low-frequent pulsatile secretion was observed for LH (a pulse occurring once every 3-8 hours) but not for FSH. While intermittent exogenous LH-RH stimulation was being performed at circhoral LH-RH pulse frequency pulsatile gonadotropin release was established at synchronous episodicity and systemic gonadotropin levels consecutively increased. These data provide indirect evidence that the pituitary gland is not rendered refractory to LH-RH by luteal progesterone secretion but readily responds to LH-RH stimuli even when these simulate a follicular phase LH-RH pulse frequency. Thus, it is concluded that spontaneous pulsatile LH release at low frequency during the luteal phase of the cycle reflects low frequent LH-RH discharges from the hypothalamus. Underlying mechanisms are discussed.     

Increased ovulation rate in androstenedione-immune ewes is not due to elevated plasma concentrations of FSH

Two experiments were undertaken to determine the hormonal response of Merino ewes to immunization against androstenedione (Fecundin). In Exp. 1 peripheral concentrations of LH, FSH and progesterone were monitored in spontaneously cycling ewes (20 immunized and 21 controls). In Exp. 2 (10 immunized and 10 controls) the same hormones were measured in ewes before and after prostaglandin (PG)-induced luteolysis and, in addition, the pattern of pulsatile LH secretion was determined during the luteal (PG + 12 days), early follicular (PG + 24 h) and late follicular (PG + 40 h) phase of the oestrous cycle. Ovulation rates were measured in both experiments. The results of these experiments indicate that androstenedione-immune animals have elevated ovulation rates (0.6-0.7 greater than control animals; P less than 0.05) associated with elevated plasma concentrations of LH and progesterone. The magnitude of the increase in plasma progesterone was correlated with androstenedione antibody titre (r = 0.6, P less than 0.001). LH pulse frequency of androstenedione-immune ewes tended to be higher at all stages of the oestrous cycle, but this difference was only significant (P less than 0.05) during the luteal phase. Mean plasma concentrations of FSH did not differ significantly between immunized and control ewes at any stage of the cycle. Analysis of periodic fluctuations in FSH during the luteal phase revealed that androstenedione-immune animals had a similar number of fluctuations of a similar amplitude to those of control animals, but the nadir of these fluctuations was lower (P less than 0.05) in immunized animals. A significant (P less than 0.05) negative correlation existed between androstenedione antibody titre and the interval between FSH peaks (r = -0.49) and androstenedione antibody titre and FSH nadir concentrations (r = -0.46). It is concluded that plasma FSH concentrations are not a determinant of ovulation rate in androstenedione-immune ewes and that increased LH concentrations, or perturbation of normal intraovarian mechanisms, may be responsible for the increase in ovulation rate observed in ewes immunized against androstenedione.     

Studies on pituitary-gonadal function in patients with Cushing's syndrome

Basal levels of sex steroids, and the responses of LH and FSH to LH-RH were studied in twenty-five female patients with Cushing's syndrome (17 Cushing's disease and 8 adrenocortical adenoma). Only two patients had a regular menstrual cycle. Amenorrhea or oligomenorrhea had been of long duration in the other cases except for three postmenopausal patients. In patients with Cushing's disease, basal estradiol was low or below normal in 86%. Progesterone was normal in 83%, but testosterone was high in half of the cases. The response of LH to LH-RH in patients with Cushing's disease was normal in 35%, low in 35% and high in 29% of the cases. FSH response to LH-RH was normal in 23.5%, low in 23.5% and high in 53%. In patients with adrenocortical adenoma, basal of estradiol was low or below normal, but progesterone and testosterone were normal in all cases. The response of LH and FSH to LH-RH in all patients with adrenocortical adenoma was higher than normal. In three postmenopausal women, a higher response of LH and FSH to LH-RH was seen in two cases and suppressed in one case. These data suggest that the main site of suppression of the gonadal axis in patients with adrenocortical adenoma is the gonad rather than the pituitary gland or hypothalamus, though the mechanism of hypogonadism in patients with Cushing's disease is heterogeneous.     

Therapeutic significance and the mechanism of action of the LH-RH agonist ICI 118630 in breast and prostate cancer

The influence of the LH-RH agonist ICI 118630 on circulating levels of the pituitary gonadotrophins LH and FSH and the gonadal steroids oestradiol, progesterone, 17-hydroxyprogesterone and testosterone has been studied in phase I clinical trials of the drug in patients with advanced breast or prostate cancer. ICI 118630 initially stimulated plasma levels of LH and FSH. On continued treatment however, the drug reversed this response and produced a rapid decline in plasma testosterone and progesterone in male and female patients respectively. Plasma oestradiol concentrations equivalent to those seen in oophorectomised or postmenopausal women were eventually produced in all 5 female patients treated with ICI 118630. In one patient however persistent follicular activity occurred until her third menstrual cycle. No appreciable side effects of the drug were observed. These data indicate that ICI 118630 initiates a castration-like endocrine response and has potential in the treatment of hormone dependent tumours of the breast and prostate.     

Unilateral cryptorchidism with compensatory hypertrophy of descended testicle in prepubertal boys.

5 prepubertal boys with unilateral cryptorchidism and compensatory hypertrophy of the descended testicle, 22 prepubertal boys with unilateral cryptorchidism and without CTH, and 14 prepubertal normal boys were submitted to LH-RH and to HCG tests in order to study the hormonal behaviour in CTH phenomenon before puberty. High but normal peaks of plasma LH and FSH were observed after LH-RH in CTH boys who showed a significant increase of testosterone after HCG stimulation. On the contrary the LH response to LH-RH and the testosterone response to HCG of the boys with unilateral cryptorchidism and without CTH were, as expected, significantly lower than in the control ones.     

Luteinizing hormone and testosterone secretory profiles of boars: Effects of stage of sexual maturation

Two short term studies of LH and testosterone secretory profiles were carried out to evaluate the effects of stage of sexual maturity on the patterns of secretion of these hormones in Large White x Landrace boars. Four pubertal and three post-pubertal boars were subjected to plasma sampling every twenty minutes for 24 hours. During puberty, plasma profiles of LH varied in a manner indicative of a highly pulsatile mode of secretion. Likewise, large fluctuations in plasma testosterone levels were noted at this age, but they were not as frequent as those of LH. In contrast, plasma LH and testosterone profiles of post-pubertal boars showed fewer and smaller fluctuations in hormone concentrations. The overall mean levels of LH and testosterone were 0.82 and 1.04 ng/ml in pubertal boars, and 0.39 and 0.81 ng/ml in post-pubertal animals. At neither age was there any evidence of diurnal variations in plasma hormone concentrations.     

Comparison of LH release and luteal function in cyclic and LH-RH-treated anoestrous ewes pretreated with PMSG or oestrogen.

Pretreatment of seasonally anoestrous Clun Forest ewes with 750 i.u. PMSG or 50 microgram oestradiol benzoate 24 or 7 h respectively before a single injection of 150 microgram synthetic LH-RH significantly increased the release of LH compared to that after injection of 150 microgram LH-RH alone. Total LH release in the two "combined" treatments was approximately 70% of that found at a natural oestrus, compared to 25% for LH-RH alone. All but one of the treated ewes ovulated, but only those pretreated with PMSG consistently produced corpora lutea capable of elevating peripheral plasma progesterone concentrations although these were lower than those at natural mid-cycle. These progesterone concentrations were, however, comparable to those during the natural cycle when corrected for the higher metabolic clearance rate found during anoestrus.     

Alcohol decreases the alpha subunit, LH and testosterone secretion in response to LH-RH]

In our previous study we showed that alcohol disturbed the circadian rhythms of LH, testosterone and its conversion to DHT. To determine the effect of LH-RH on pituitary-gonadal function before and after alcohol, 11 male volunteers aged 24-29 years (mean 25.5) were investigated. Blood for hormonal estimations was withdrawn before and 20, 30, 60, and 120 min after LH-RH. In every case, the LH-RH test was performed twice: 6 hours after placebo and, a week later, 6 hours after alcohol administered orally, in dose of 1.0 g/kg bw. The LH, FSH, alpha-subunit and testosterone concentrations were measured with radioimmunological methods. Results: It was shown that alcohol significantly inhibited LH (p < 0.05), alpha-subunit (p < 0.02) and testosterone (p < 0.001) response to LH-RH stimulation, but not that of FSH.     

四眼斑水龟血浆生殖激素季节性变化

为了进一步探讨四眼斑水龟(Sacalia quadriocellata)的繁殖生理周期和生殖激素分泌特征,使用放射免疫分析测定法(RIA)分别测定了8月(夏季)、10月(秋季)、1月(冬季)、3月(春季)四眼斑水龟血浆中卵泡刺激素(FSH)、促黄体生成素(IJH)、睾酮(T)、雌二醇(E2)、孕酮(P)五种生殖激素的含量.结果显示,四眼斑水龟生殖激素分泌呈现较明显的周期性,激素水平与环境温度的变化有关;雄性T含量夏季开始升高,秋季达到高峰,与精子的发生和成熟同步;雌性T水平升高促进其接受雄性爬胯,且作为雌激素合成的前体物质,间接作用于雌激素的合成;排卵会出现LH峰,E2含量排卵前几个月开始增长,刺激肝生成卵黄;排卵期间P含量较高,可能在排卵过程中发挥作用.     

Site of negative feedback action of estrogen on gonadotropin secretion in normal women

We have reported that iv administration of conjugated estrogens results in no significant change in the plasma LH-RH level during the negative feedback phase of LH, suggesting that estrogen does not suppress LH by decreasing hypothalamic LH-RH. To determine the site of estrogen action during the negative feedback phase, we studied the pituitary response to a small amount of LH-RH after estrogen administration in normal cyclic women in the mid-follicular phase. The pituitary responses to an iv bolus of 2.5 micrograms of synthetic LH-RH were evaluated by measuring serum LH and FSH 2 h before and 8 h after administration of 20 mg of conjugated estrogens (Premarin). The mean levels of serum LH and FSH were significantly (p less than 0.05) decreased 8 h after the injection. The peak responses of LH and FSH to LH-RH were also significantly (p less than 0.05) reduced after Premarin administration. These findings suggest that the negative feedback effect of estrogen on gonadotropin secretion is caused by its direct suppression on the pituitary response to LH-RH.     

Effects of exogenous testosterone on testicular luteinizing hormone and follicle-stimulating hormone receptors during aging

During aging, the male Japanese quail exhibits a loss of fertility, increased morphological abnormalities in the testes, and a higher incidence of Sertoli cell tumors. Although there is a coincident loss of reproductive behavior, plasma androgen levels remain high until testicular regression occurs in association with senescence. The purpose of this study was to compare mean specific binding of chicken luteinizing hormone (LH) and follicle-stimulating hormone (FSH) as a measure of testicular receptors during identified stages during aging. Males were categorized according to age (young = 9 months, middle aged = 24 months, or old = 36+ months) and sexual behavior (active or inactive). Testicular samples were collected immediately after perfusion with 4% paraformaldehyde from the following groups: young active (n = 8), young photoregressed (n = 5), young photoregressed plus testosterone implant (n = 4), middle-aged active (n = 8), middle-aged inactive (n = 4), old inactive (n = 5), and old inactive plus testosterone implant (n = 6). A crude plasma membrane fraction was prepared from the testes of each bird and an aliquot deriving from 10 mg of testicular tissue was used for binding assay. Specific binding of labeled LH or FSH was expressed as percentage of total radioactive hormone. Results showed significant (P < 0.05) age-related decreases in both FSH and LH receptor numbers. The highest FSH binding was found in young and middle-aged active males, with low binding in old inactive males. Testicular LH binding decreased during aging, with a sharp decrease in middle-aged males, which was similar to old males. Testosterone implants weakly stimulated FSH and LH binding in old males. Both LH and FSH binding decreased in photoregressed young males. However, testosterone implants stimulated increased LH binding, but did not affect FSH binding in young photoregressed males. These results provide evidence for separate regulation of testicular LH and FSH receptors, with testosterone stimulation of LH receptor, but not FSH receptor number in young males. However, during aging there appears to be a loss of this response, potentially because of the reduced efficacy of testosterone stimulation, thereby implying a diminished capacity for response with aging.     

Pituitary responsiveness to synthetic LH-RH and pituitary LH content at various reproductive stages in the sheep.

In sheep the basal concentration of LH in jugular vein plasma was significantly higher during the first 50 days of gestation in late pregnancy or at parturition. The pituitary response to a single i.v. injection of 200 microng synthetic LH-RH was determined at different stages of gestation and compared with that of anoestrous and cyclic sheep. Pituitary response to LH-RH decreased progressively with advancing gestation: by 56 days after mating the response had declined to 35% and by parturition to 14% of the value in anoestrous sheep. The pituitary response to LH-RH increased after parturition and the pattern of recovery differed in non-lactating and lactating sheep. By 63 days postpartum the response to LH-RH in non-lactating and lactating animals had returned to values similar to those in sheep during anoestrus and sheep during the luteal phase of the oestrous cycle. A decrease in pituitary responsiveness during pregnancy was associated with a decrease in pituitary content of LH. The quantity of LH released in response to a standard injection of LH-RH was linearly related to pituitary LH content.     

Seasonal changes in plasma concentrations of immunoreactive inhibin and testicular activity in male Japanese monkeys

Seasonal changes in plasma immunoreactive (ir-) inhibin, testosterone, LH, and FSH concentrations were examined in five sexually mature male Japanese monkeys (Macaca fuscata fuscata) housed indoors individually, to explore the reproductive cyclicity in the male. Blood samples were collected monthly throughout one year, and testicular size, semen volume, and number of sperm in the semen were ascertained at the same time in the same animals. Semen samples were obtained by penile electrostimulation. The results showed a clear seasonal increase in all parameters: plasma ir-inhibin, testosterone, testicular size, semen volume, and total number of sperm in the liquid portion of the semen during the autumn and winter months in synchrony with the natural breeding season. In contrast, plasma LH and FSH remained unchanged throughout the year, although plasma FSH tended to increase during the breeding season concomitant with an increase in plasma ir-inhibin. A significant positive correlation between FSH and ir-inhibin was observed in two of five monkeys. The positive correlations between plasma ir-inhibin and testicular activities during both the developing and regressing phases of the testicular cycle indicate that plasma ir-inhibin is a useful indicator of testicular activity as well as an indicator of Sertoli cell function in the Japanese monkey.