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At least 325 records · Page 18Linked to original sources
PubMed1986

Effect of graded doses of gonadotrophin-releasing hormone on serum LH concentrations in mares in various reproductive states: comparison with endogenously generated LH pulses.

Luteinizing hormone release induced by a range of small (3.3-33 micrograms) and large (300-500 micrograms) i.v. doses of gonadotrophin-releasing hormone (GnRH) was measured in acyclic (n = 4), luteal phase (n = 3) and follicular phase (n = 5) mares and compared with endogenously generated LH pulses in the same reproductive states. Extrapolation from log-linear dose-response curves showed that an LH pulse comparable to an endogenous one would be simulated by i.v. injection of 7.0 (n = 4) and 4.1 (n = 6) micrograms GnRH in luteal and follicular phase mares respectively; a much smaller dose than the 500 micrograms usually given clinically or experimentally. In acyclic mares (n = 4), LH pulses occurred too infrequently to be characterized. At small doses of GnRH the amount of LH released by the same dose was similar in all three reproductive states, although the steroid hormone milieu differed markedly. This implies that observed differences between states in mean (+/- S.E.M.) serum LH concentrations (0.7 +/- 0.01, 1.2 +/- 0.03 and 11.6 +/- 0.33 (microgram/l) in acyclic, luteal and follicular phase mares respectively) were produced by differences in GnRH pulse frequency and/or amplitude and not by steroid-mediated changes in pituitary response to GnRH. In acyclic, luteal and follicular phase mares, LH pulse frequency was: immeasurably low, 0.09 and 1.14 pulses/h respectively, which supports the important contribution of pulse frequency to determining mean LH concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of long- and short-term gonadectomy on the hypothalamo-hypophysial (LH-releasing hormone-LH) system in oestrogen-treated male and female rats.

Considerable differences have previously been found in the hypothalamo-hypophysial responsiveness to oestrogen, depending upon the time between gonad removal and exposure to oestrogen. In the present study a detailed analysis was made of some of the differences which may exist in pituitary LH-releasing hormone (LHRH) receptors and the amount of LH released in response to electrochemical depolarization of the medial preoptic area after 2 or 7 days of oestradiol treatment of long- and short-term gonadectomized male and female rats. The pituitary glands of long-term gonadectomized males and females secreted more LH in response to two pulse injections of LHRH than did short-term gonadectomized rats. The amount of LH released on day 2, however, was equivalent to that secreted after 7 days of oestradiol treatment. Moreover, long-term gonadectomized males and females had equivalent LHRH receptor concentrations, which were greater than those of short-term gonadectomized animals. Peak serum LH concentrations observed after preoptic stimulation were equivalent in short- and long-term castrated rats after 2 days of oestrogen exposure. Serum LH concentrations following preoptic stimulation in short-term gonadectomized males and females were significantly greater on day 7 than on day 2 of oestradiol treatment, whereas in long-term gonadectomized animals the stimulated release of LH was equivalent both in magnitude and time of peak release on both days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Immunoreactive beta-core-like material in normal postmenopausal urine: human chorionic gonadotrophin or LH origin? Evidence for the existence of LH core.

Material with the immunochemical properties of the beta-core of human chorionic gonadotrophin (hCG) can be found in the urine of normal postmenopausal women. However, we have been unable to detect intact hCG (using an assay which is specific for the alpha-beta heterodimer of intact hCG) in serum of such subjects. The levels of serum LH and urinary beta-core were compared in matched samples from 28 women (serum LH: median 27 U/l, range 4-70 U/l, urinary beta-core: median 0.27 microgram/l, range less than 0.05-0.645 microgram/l). Urine (4 litres) from three postmenopausal women was concentrated, dialysed and subjected to gel exclusion chromatography on Sephadex G-100. Fractions were analysed by specific assays for LH, intact hCG, total beta-hCG (free beta-subunit and intact hCG), free alpha-subunit and beta-core. Material eluting at the expected position of the beta-core fragment of hCG was detected in all three samples by the beta-core, beta-hCG and LH assays, despite the fact that the LH antibody does not recognize the authentic beta-core of pregnancy. Electrophoresis and Western blotting of the concentrated urines revealed that material of the same molecular size as beta-core was recognized by the antibody to LH but not by a monoclonal antibody raised to free beta-hCG which also recognizes the beta-core molecule of hCG. We conclude that the predominant core-like material identified in postmenopausal urine is probably derived from the beta-subunit of LH.

Aged↗
PubMed2001

Presence of LH in gonadotropins associated with higher IVF pregnancy rates when basal serum LH is increased.

PURPOSE: To determine if pregnancy rates following in vitro fertilization-embryo transfer (IVF-ET) correlate with the presence or not of luteinizing hormone (LH) in the gonadotropins used for stimulation. Furthermore to see if the early follicular phase serum LH level affects pregnancy outcome according to the type of gonadotropins used. METHODS: The type of gonadotropins were prescribed randomly according to finances and convenience. Serum LH was obtained on day 2 or 3 of the menstrual cycle. RESULTS: When LH was > the median, significantly higher pregnancy rates were obtained in those treated with the follicle stimulating hormone (FSH)/human menopausal gonadotropin combination. When LH was < or = the median, significantly more oocytes were retrieved with FSH exclusively. No confounding variables were found to explain the data. CONCLUSIONS: Considering concerns of published studies that LH may have a toxic effect on pregnancy outcome, and if LH is suppressed too low, gonadotropins with exclusive FSH may not stimulate sufficient oocytes, the results were opposite to expectations.

Adult↗
PubMed1992

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

UNLABELLED: 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.

Adult↗
PubMed2004

[Antagonist protocols: residual LH levels and the value of exogenous LH supplementation].

When administered in the late follicular phase to prevent any LH surge, GnRH antagonists induce a sharp decrease in serum LH levels that may be detrimental for assisted reproductive technology cycle outcome. This decrease in LH levels is dose-dependant. Supplementation with recombinant LH when introducing GnRH antagonist leads to significant changes in E2 secretion. This is consistent with a key role of LH to ensure adequate steroidogenesis. This also indicates that a single dose of GnRH antagonist is able to decrease bioactive LH below a minimal threshold for optimal steroidogenesis. However, supplementation with rLH does not modify the number of retrieved oocytes, obtained embryos and the pregnancy rate. This is in line with the concept that folliculogenesis is mainly dependent on FSH and that the role of LH and E2 is not primordial. Indeed, the findings of our prospective randomized study do not support a systematic supplementation with rLH when introducing antagonist. However, further studies are necessary to determine whether a specific sub group of patients characterized by a low E2/oocyte ratio could benefit from rLH supplementation.

Adult↗
PubMedDate not supplied

Effect of oral estriol on abnormal plasma FSH and LH concentrations in women with unexplained infertility; conception in a patient with elevated FSH and LH.

Estriol tablets in the daily dose of 0.25, 0.5 or 1.0 mg were administered for ten days prior to the expected ovulation in six women with unexplained, long-standing infertility, regular, apparently ovulatory cycles, and normal cyclic changes in estradiol and progesterone. Five of six had abnormal FSH and LH patterns contrasting with normal estradiol and progesterone secretion during the control cycle. There was an increase in the midcycle LH surge at two lower doses of estriol and at the highest dose there was a 7-9 day delay observed in the estradiol peak, LH surge and menstrual period in the patient with the normal control cycle. This contradicts previously published data that estriol does not suppress or delay ovulation at the dose as high as 6 mg/day. In four patients with persistently elevated LH and low FSH concentrations, there was little change in the pattern of FSH, LH, estradiol or progesterone secretion during treatment. In the last patient, who had during the control cycle plasma FSH and LH concentrations fluctuating between high normal and menopausal range, indicating "premature ovarian failure" and absence of ovarian follicles, essentially normal cyclic pattern of both gonadotropins with exception of few individual values appeared during treatment. The patient conceived during the last cycle of treatment (estriol 1.0 mg/day). Our study demonstrates that high concentrations of FSH and LH may not necessarily indicate the absence of oocytes and documents previously reported, but never documented occurrence of a conception during estrogen therapy in such a case.

Dose-Response Relationship, Drug↗
PubMed1976

Pituitary and testicular response to hypothalamic LH-releasing hormone (LH-RH) in normal and oligospermic men.

A comparative study was done of the basal and post-LH-RH stimulation levels of LH, FSH and Testosterone (T) in 10 healthy, male volunteers, aged 24-35 years, and in 25 normogonadotropic oligospermic men aged 23-43 years in whom other endocrine, urologic and/or vascular diseases had been rules out. Seventeen of the latter group underwent bilateral testicular biopsy. Each subject received rapid i.v. injection of 50 mug synthetic LH-RH at 8:00 A.M. Serum levels of LH, FSH and T were determined by radioimmunoassay on samples obtained immediately before and 30 and 45 minutes after injection. As compared to normals, oligospermic men had a lower average LH response, although the basal values did not differ significantly from normal. FSH levels did not differ significantly between groups, although some individual patients showed higher and some lower than normal values. The possibility of stimulating T secretion with LH-RH was confirmed. Average serum T levels rose more slowly and reached lower levels in the oligospermic men than in normal men. There was no correlation between LH and FSH rises. It is postulated that some patients with normogonadotropic oligospermia may have latent insufficiency of pituitary gonadotropic functional reserve for one or both hormones and/or of the Leydig cell function. The need for individual analysis of results and their correlation with testicular biopsy findings is commented.

Adult↗
PubMed1997

Urinary LH, plasma LH and progesterone and their clinical correlates in the periovulatory period of domestic bitches.

Ten bitches were examined daily from pro-oestrus until metoestrus to correlate endocrine, vaginoscopic and cytological assessments of stage of the oestrous cycle. It was considered that oocytes were fertile by 4 days after the LH peak assuming a 2 day lag before ovulation and a further 2 days for oocyte maturation. Eight bitches showed a plasma LH peak and five bitches showed a peak in urinary LH, which corresponded to the plasma LH peak. Plasma concentration of progesterone increased in all bitches. Initially, this coincided with the preovulatory LH peak and reached values of 7.7 +/- 0.6 ng ml-1 4 days later. The peak in number of a nuclear vaginal epithelial cells and the onset and peak of vaginal mucosal shrinkage with angulation occurred on average 2.4 +/- 1.5, 2.1 +/- 2.4, and 6.1 +/- 1.1 days after the plasma LH peak, respectively, giving sufficient precision to be of practical value in estimating the fertile period. However, the onset of vulval softening, changes in rectal temperature and colour of the vulval discharge varied considerably. Nine of the bitches were mated at the time of highest percentage of a nuclear cells, coinciding with the onset of the period of vaginal mucosal shrinkage with angulation. Eight became pregnant. Selected clinical parameters are therefore useful in predicting the optimal mating time of bitches, as is detection of plasma progesterone concentration higher than about 8 ng ml-1, but the latter appears to be the most reliable method. Detection of the urinary LH peak was more difficult and as yet offers no practical advantages except from the point of view of easy sample collection.

Animals↗
PubMed1986

Hyperprolactinemia enhances LH-stimulated 4-ene-5 alpha-reductase activity but inhibits LH-induced 17-hydroxylase activity in testes of hypophysectomized immature rats.

Two pituitaries from 7-week old female rats (Sprague-Dawley strain) were grafted under the capsule of the left kidney of 21-day old male rat. The pituitary grafted and sham-operated rats were hypophysectomized at 27 days of age. The hypophysectomized rats, in groups of 4, were given daily injections of 9 micrograms NIAMDD-oLH-23 (minimum effective dose) or saline for 3 days starting from day 29. Testicular homogenates were incubated with [3H]progesterone or [14C]4-androstene-3,17-dione, and enzyme activities per testes were estimated. Testicular HCG-binding sites were also measured. Hypophysectomy caused significant decreases in activities of testicular 5 alpha-reductase, 17-hydroxylase, and 17 beta-hydroxysteroid oxidoreductase. These decreased enzyme activities were significantly stimulated by LH treatment. Although pituitary grafts alone showed no effects on these enzyme activities in the testes of the hypophysectomized rats, the grafts significantly enhanced LH-stimulated 5 alpha-reductase activities but inhibited LH-stimulated 17-hydroxylase activity. Testicular LH/HCG receptors were significantly increased by the grafts, especially in the presence of LH, without affecting affinity for HCG. The present results demonstrate for the first time that hyperprolactinemia directly stimulates LH-stimulated 5 alpha-reductase activity in rat testes. The results also show that the same grafts directly inhibit LH-stimulated 17-hydroxylase activity, probably via postreceptor mechanisms.

17-Hydroxysteroid Dehydrogenases↗
PubMed2000

Male hypogonadism caused by homozygous deletion of exon 10 of the luteinizing hormone (LH) receptor: differential action of human chorionic gonadotropin and LH.

We report the unique case of a patient with Leydig cell hypoplasia (LCH) type II caused by a genomic deletion resulting in the complete absence of exon 10 of the LH receptor (LHR). The patient presented at the age of 18 yr with retarded pubertal development, small testicles, and delayed bone maturation. LH was highly elevated, with very low serum testosterone levels. Genetic analysis revealed a homozygous deletion of approximately 5 kbp encompassing exon 10 of the LHR gene. Screening of family members demonstrated heterozygosity for the deletion, indicating autosomal recessive inheritance. At the time of examination, the patient displayed nearly normal male phenotype, but lacked pubertal development and was hypogonadal. Obviously, fetal male development sustained by hCG was normal, whereas LH action, important for pubertal development, was impaired. A hCG stimulation test induced testosterone biosynthesis and secretion within the normal range. Subsequently, hCG treatment was continued, resulting in an increase in testicular volume and the appearance of spermatozoa in the ejaculate after 16 weeks of treatment (5.3 million/mL). Despite highly elevated endogenous LH serum levels, the response to hCG indicates a possible dual mechanism of hormone binding and signal transduction for hCG and LH on a LHR that lacks exon 10. Furthermore, this patient represents the clinical counterpart of the normal male marmoset monkey (Callithrix jacchus), in which the expressed LHR lacks exon 10 in toto. This case provides important clinical insights about the possible role of exon 10 of the LHR in discriminating between LH and hCG actions.

Adolescent↗
PubMed1989

Increases in testosterone secretion in adult rams with immunoneutralization of endogenous estradiol occur in the absence of increases in pulsatile LH release or testicular LH receptors.

The testes of the ram become more responsive to LH stimulation following immunoneutralization of endogenous estradiol. The possibility that testosterone secretion is facilitated by increased LH-binding activity in the testes was investigated in the present study conducted with adult Dorset X Leicester X Suffolk rams during the time of testicular recrudescence. Patterns of episodic LH release and testosterone secretion (days--5, 10 and 24) and LH-binding activity in testicular biopsy samples (days--1, 14 and 28) were assessed on the days indicated relative to the onset of passive immunization and the establishment of relatively low titres (approximately 1:200) of estradiol antiserum. During the experimental period, mean serum testosterone concentration increased by approximately 150% for the immunized rams as basal concentration and pulse amplitude increased, while all characteristics of testosterone secretion remained unchanged for the nonimmunized rams. Characteristics of LH release and the concentration of LH-binding sites in the testes, however, were always similar for both groups of rams. Further, group differences in FSH and PRL secretion and in the concentration of testicular FSH-binding sites did not occur. These results provide evidence for an estradiol direct (gonadotropin independent) negative-feedback component in the regulation of Leydig cell function in the ram.

Animals↗