The physiology of gonadotropin-releasing hormone (GnRH) secretion in men and women.
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Amenorrhea↗
Biomedical subjects
W F Crowley
Publications and source records attributed to W F Crowley.
The effects of the aromatase inhibitor delta 1-testolactone on gonadotropin release and steroid metabolism in polycystic ovarian disease.
This study was designed to examine the importance of aromatization in the gonadotropin secretory dynamics of polycystic ovarian disease (PCOD) by using the aromatase inhibitor delta 1 testolactone (TL) as a probe and to determine the effects of TL on steroid metabolism in vivo and in vitro. The pulsatile patterns of gonadotropin secretion and peripheral steroid levels were studied in eight women with PCOD before and during TL administration. There was a significant fall in peripheral estrone (E1) levels, a rise in peripheral androstenedione levels, and an increase in the androstenedione/E1 ratio during TL administration in these women. Isotopic determinations of androgen and estrogen production and metabolism before and during TL administration in two women confirmed a 90-95% decrease in the overall rate of aromatization. One patient also had an increase in the production and clearance rates of estradiol and E1 during TL administration, suggesting resistance to TL of the ovarian aromatase enzyme system. There were significant increases in both mean LH pulse amplitude [1.2 +/- 0.3 (SE) mIU/ml LER-907 before vs. 1.7 +/- 0.3 mIU/ml LER-907 during TL, P less than 0.05, paired t test] and frequency per 6 h (median: 3 before vs. 4 during TL, P less than 0.05, Wilcoxon signed rank test). Mean levels of LH and FSH did not, however, change significantly during TL administration. TL maximally inhibited neonatal rat hypothalamic aromatase in vitro at concentrations of 200 microM, a level theoretically obtainable during pharmacological therapy. These data suggest that: 1) in humans TL is a potent inhibitor of peripheral but not ovarian aromatase, and of hypothalamic aromatase in rats; 2) TL administration increases LH pulse amplitude and frequency in PCOD, either directly via hypothalamic aromatase inhibition, or indirectly by alterations in gonadal steroid metabolism; and 3) because of the multiple potential actions of TL, its usefulness as a probe in studies of gonadotropin secretion in PCOD is limited.
Adult↗
Pituitary luteinizing hormone responses to intravenous and subcutaneous administration of gonadotropin-releasing hormone in men.
Although differences in plasma GnRH concentrations have been identified after iv and sc injection of this peptide, differences in pituitary LH responses to iv and sc GnRH have not been evaluated in detail. We studied the magnitude and contour of plasma GnRH and LH responses after low doses of iv and sc GnRH administered to men with idiopathic hypogonadotropic hypogonadism and compared them to LH pulses in normal men after endogenous GnRH secretion. Mean areas under the LH response curves differed significantly (P less than 0.01) after 25 ng/kg, but not 250 ng/kg, iv and sc GnRH doses. The mean time from basal to peak plasma LH concentrations was significantly longer with sc than iv GnRH (P less than 0.02). In addition, individual LH responses were more variable with sc GnRH. Intravenous administration produced greater GnRH amplitude (P less than 0.001) and area under the curve (P less than 0.005) and shorter time to peak (P less than 0.01) GnRH concentrations. When plasma LH responses of similar area and amplitude were compared, the contour of LH responses after iv GnRH more closely simulated the LH pulses in normal men. These data demonstrate that 1) significant differences exist in the amplitude, contour, and variability of plasma LH and GnRH pulses after iv and sc GnRH; and 2) iv GnRH elicits LH secretory episodes which closely resemble endogenous pulsations of normal men. These results suggest that iv GnRH administration may be preferred in physiological studies and, if the data can be extrapolated to women, may account for the greater success of ovulation induction reported with iv GnRH.
Adolescent↗
Neuroendocrine control of reproduction and its therapeutic manipulation with GnRH and its analogs.
The hypothalamus mediates the neuroendocrine control of reproduction in both males and females through pulsatile secretion of GnRH. The anterior pituitary gland, in turn, appears to require this episodic GnRH stimulation in order to secrete the gonadotropins LH and FSH in a physiologic fashion. Deficiency of GnRH manifests as a failure to attain puberty in both sexes, and in females it may also produce amenorrhea and/or anovulation. Replacement regimens of GnRH which employ an episodic pattern of delivery correct the deficiency of endogenous GnRH secretion and stimulate gonadotropin secretion, gonadal steroidogenesis and gametogenesis. However, continuous occupancy of the GnRH receptor by native GnRH and/or its long-acting analogs paradoxically inhibits pituitary gonadotropin secretion. GnRH analogs have been synthesized which exhibit greater affinity and prolonged occupancy on the GnRH receptor and can produce pituitary desensitization of gonadotropin secretion. Chronic administration of these GnRH analogs is capable of producting a selective "medical castration." Thus, by altering the frequency of episodic GnRH administration or by utilizing long-acting GnRH analogs it is possible to stimulate or suppress the neuroendocrine control of reproduction. The use of GnRH or its long-acting analogs has demonstrated a profound clinical impact in restoring or inhibiting fertility.
Adolescent↗
Clinical, biochemical, and ovarian morphologic features in women with acanthosis nigricans and masculinization.
Nine women with acanthosis nigricans and masculinization, who did not appear to have any of the reported syndromes associated with acanthosis nigricans, were studied to characterize the clinical, biochemical, and ovarian morphologic features of their disorders. These patients had the clinical and biochemical profiles of polycystic ovarian disease. All acanthosis nigricans subjects had significant insulin resistance when insulin binding to both circulating monocytes and erythrocytes was compared to the control subjects. Microscopic examination of the ovaries revealed no evidence of recent normal ovulation, sclerosis of the ovarian cortex, follicle cysts, and stromal hyperthecosis. The authors conclude that ovarian stromal hyperthecosis and insulin resistance are consistent findings in the present type of patient. This study provides further evidence supporting a relationship between insulin resistance and human ovarian function.
Acanthosis Nigricans↗
Neuroendocrine regulation of the corpus luteum in the human. Evidence for pulsatile progesterone secretion.
The pattern of episodic gonadotropin release was studied in 15 normal female volunteers during the luteal phase of the menstrual cycle with 24 h of blood sampling for follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels at 10-min intervals. Six subjects (two in the early, two in the mid-, and two in the late luteal phase) also had each of these specimens processed for progesterone levels. A progressive slowing of LH pulsations was present across the luteal phase with the mean LH pulse frequency declining from 15.2 pulses/24 h in the early to 8.4/24 h in the late luteal phase. A trend towards reduction in the amplitude of LH pulses was also observed (12.3 +/- 2.2 SD mIU/ml in the early vs. 8.6 +/- 3.4 mIU/ml in the late luteal phase; NS). In addition, LH pulses of heterogeneous amplitude were identified during the same 24-h study. The mean +/- SD of the larger and of the smaller LH pulses was 16.9 +/- 4.7 and 2.3 +/- 1.0 mIU/ml, respectively (P less than 0.001). While the slowing of the frequency of all LH pulses correlated well (r = 0.80, P less than 0.001) with the day of the luteal phase and poorly with the actual plasma progesterone levels, the incidence of the small LH pulses was highest in the mid-luteal phase and correlated well with the mean progesterone plasma levels (r = 0.63, P less than 0.01). In the early luteal phase, the pattern of progesterone secretion was stable over the 24-h studies and showed no relationship to episodic LH release. In contrast, in the mid- and late luteal phase, plasma progesterone concentrations rapidly fluctuated during the 24-h studies from levels as low as 2.3 to peaks of 40.1 ng/ml, often within the course of minutes. Progesterone increments closely attended episodes of LH release, as documented by the significant (P less than 0.05) cross-correlation between LH and progesterone levels, at time lags of 25-55 min. The results of this study indicate that in the human luteal phase: (a) the frequency of pulsatile release of LH declines progressively and correlates well with the duration of exposure to progressively and correlates well with the duration of exposure to progesterone; (b) the amplitude of LH pulses varies with the appearance of an increased percentage of smaller pulses correlating well with the acute level of progesterone; (c) in the early luteal phase, the pattern of progesterone secretion is stable; (d) in the mid- and late luteal phase, progesterone secretion is episodic, and correlates with LH pulsatile release; and (e) single progesterone estimations in the mid- and late luteal phase do not accurately reflect corpus luteum adequacy.
Corpus Luteum↗
The effects of continuous androgen secretion on the hypothalamic-pituitary axis in woman: evidence from a luteinized thecoma of the ovary.
Hyperandrogenic states in women are often accompanied by disruption of gonadotropin secretion. However, the role of androgens per se in the pathogenesis of this abnormality is poorly understood. We report a woman with a virilizing ovarian tumor in whom the effects of continuous androgen secretion on the hypothalamic-pituitary axis were investigated in detail. A 29-yr-old woman with previously normal reproductive function, including prior fertility, was evaluated for amenorrhea and hirsutism. She had elevated peripheral serum levels of testosterone (T; 337-500 ng/dl) and androstenedione (A; 258-353 ng/dl). Her serum LH level was above the normal follicular phase range and was hyperresponsive to LHRH, whereas the FSH level was below normal early follicular phase levels and increased minimally in response to LHRH. A luteinized thecoma of the left ovary, shown by catherization of the ovarian venous blood to be secreting both T and A, was removed. Postoperatively, serum T and A levels returned to normal, and the patient had a normal ovulatory menstrual cycle in the 30 days after the operation, documented by daily determinations of plasma estradiol, progesterone, and gonadotropin levels. A repeat LHRH test in the follicular phase of the second postoperative menstrual cycle was completely normal. This case indicates that the characteristic abnormalities of gonadotropin secretion observed in hyperandrogenic states such as polycystic ovarian disease can result from chronic androgen secretion by an ovarian tumor and that normal folliculogenesis and gonadotropin secretion can be promptly restored by the elimination of the androgen excess.
Adrenocorticotropic Hormone↗
An overview of LHRH and its analogues: clinical uses.
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Adolescent↗
The study of GnRH control of reproductive function.
The activity of the hypothalamic-pituitary-gonadal (HPG) axis is controlled by gonadotropin-releasing hormone (GnRH). GnRH, gonadotropins, and gonadal sex steroids are secreted in a pulsatile fashion. As the peripheral plasma concentrations of GnRH are too low for the existing assay systems, the pattern of pulsatile release of gonadotropins is often utilized for the indirect estimation of hypothalamic GnRH activity. In addition, the long-term pulsatile administration of exogenous GnRH in selected states of GnRH deficiency provides important information on the regulation of the HPG axis. Because of the limits of each approach, both investigational tools should be used complementary for the study of GnRH role in the control of pituitary and gonadal function. This article reviews recent information on GnRH physiology acquired with the use of these methods.
Animals↗
Gonadotropin-releasing hormone: molecular and cell biology, physiology, and clinical applications.
The observations in recent years that gonadotropin-releasing hormone ( pyroGlu1 -His2-Trp3- Ser4 -Tyr5- Gly6 -Leu7-Arg8-Pro9- G ly10NH2 [GnRH]) has considerable clinical efficacy as a contraceptive, an ovulation-inducing agent, and a drug that is useful in the therapy of a number of diseases are owed in no small part to advances that have been made in the basic molecular biology and physiology of this peptide. It is reasonable then that this symposium should be broken down into three separate yet integrated areas: 1) the molecular and cellular biology of GnRH, 2) the physiology of GnRH, and 3) the clinical efficacy of this compound. A number of recent advances have helped the progress of work in all three of these areas. The observation that substitution of a D-amino acid in the sixth amino acid position leads to considerable metabolic stability and reduced degradation of releasing hormone analogs has been especially useful. In addition, the observation that the further derivatization of such substituted compounds by deletion of the 10th amino acid and addition of an ethylamide group to Pro9 has resulted in compounds with a markedly increased ability to bind to the receptor. These compounds have been useful clinically and have allowed development of radioligand assays to be used in animal studies and in vitro. The availability of a large number of agonists and antagonists has allowed formulation of molecular models for GnRH and resulted in development of clinically useful compounds. In a short paper of this nature we cannot hope to provide an encyclopedic review; rather we hope to provide an overview and offer references to the literature for those who wish a more in-depth treatment.
Aging↗
Long-term treatment of central precocious puberty with a long-acting analogue of luteinizing hormone-releasing hormone. Effects on somatic growth and skeletal maturation.
The gonadotropin-releasing hormone-like agonist D-Trp6-Pro9-NEt-LHRH (LHRHa) has been shown to induce a reversible short-term suppression of gonadotropins and gonadal steroids in patients with central precocious puberty. Since accelerated statural growth and bone maturation are clinical features of precocity not well controlled by conventional therapies, we examined the effects of prolonged LHRHa therapy for 18 consecutive months on growth and skeletal maturation in nine girls with neurogenic or idiopathic precocious puberty. Suppression of gonadotropin pulsations and gonadal steroids was maintained in all subjects. Growth velocity fell from a mean rate (+/- S.E.M.) of 9.35 +/- 0.64 cm per year during the 19 months before treatment to 4.58 +/- 0.60 cm per year during treatment (P less than 0.001). Bone age advanced a mean of 9.4 +/- 2.3 months during treatment. These changes resulted in a mean increase of 3.3 cm in predicted height (P less than 0.01). Complete suppression of the pituitary-gonadal axis can be maintained by LHRHa therapy, resulting in slowing of excessively rapid growth and skeletal maturation and in increased predicted adult height in girls with precocious puberty.
Age Determination by Skeleton↗
A conservative approach to the management of uterine leiomyoma: pituitary desensitization by a luteinizing hormone-releasing hormone analogue.
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Adult↗
Induction of puberty in men by long-term pulsatile administration of low-dose gonadotropin-releasing hormone.
Puberty is heralded by the appearance of episodic gonadotropin secretion. Men with idiopathic hypogonadotropic hypogonadism have an abnormality in gonadotropin release and do not undergo normal puberty. Since idiopathic hypogonadotropic hypogonadism is thought to represent a disorder of gonadotropin-releasing-hormone (GnRH) secretion, we used long-term low-dose subcutaneous GnRH, administered in an episodic fashion by a portable infusion pump, in an effort to establish a normal adult pattern of gonadotropin secretion in six men. All subjects noted spontaneous erections, nocturnal emissions, and breast tenderness, which were associated with elevations of serum testosterone levels (77 +/- 13 ng per deciliter [mean +/- S.E.] before therapy vs. 520 +/- 182 ng after one month of treatment; P less than 0.001). Gonadotropin levels rose to normal adult ranges within one week of therapy and to supraphysiologic levels by 14 days. Testis size increased in four patients, and spermatogenesis was achieved in three patients by 43 weeks of therapy. These results suggest that long-term episodic GnRH administration can reverse idiopathic hypogonadotropic hypogonadism.
Adolescent↗
Spatial ability in androgen-deficient men.
Several lines of previous evidence have suggested that androgens affect cognitive abilities. In an effort to characterize this defect, we compared 19 men with idiopathic hypogonadotropic hypogonadism with 19 control men and with five men with acquired hypergonadotropic hypogonadism that had developed after puberty. The 19 patients with idiopathic hypogonadism had markedly impaired spatial ability in comparison to either controls or subjects with acquired hypogonadism (P less than 0.05). Moreover, the spatial ability of the patients correlated positively with their testicular volume (P less than 0.05). Androgen-replacement therapy in six of the patients did not improve their spatial ability. The impairment in spatial ability in men with the idiopathic form of hypogonadotropic hypogonadism, the lack of such an impairment in men with the acquired form, and the failure to exogenous androgens to correct the deficits in the idiopathic form suggest that androgens exert a permanent organizing influence on the brain before or at puberty in boys.
Adult↗
Short-term treatment of idiopathic precocious puberty with a long-acting analogue of luteinizing hormone-releasing hormone. A preliminary report.
The uncoupling of pituitary stimulation and response observed in adults during administration of the luteinizing hormone-releasing hormone analogue, D-Trp6-Pro9-NEt-LHRH (LHRHa) suggested that this drug might be useful in treating precocious puberty. We treated five girls with idiopathic precocious puberty (ages two to eight) for eight weeks with daily subcutaneous injections of LHRHa. The patients had Tanner II to IV pubertal development, advanced bone age, an estrogen effect on vaginal smear, measurable basal gonadotropin levels with pulsed nocturnal secretion, and a pubertal gonadotropin response to LHRH. Irregular vaginal bleeding was present in three patients. LHRHa significantly decreased basal (P less than 0.025) and LHRH-stimulated (P less than 0.01) gonadotropin levels as well as serum estradiol (P less than 0.05). The vaginal maturation-index score, which reflects the estrogen effect, fell by 25 per cent. Eight weeks after stopping treatment, all hormonal values and the vaginal maturation index had returned to pretreatment levels. These favorable short-term results will need further study before the benefits and risks of chronic treatment with LHRHa can be adequately assessed.
Child↗
Development of a male contraceptive--a beginning.
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Contraceptive Agents, Male↗
Perifused pituitary cultures: a model for LHRH regulation of LH secretion.
In this paper, a dispersed anterior pituitary cell system that is continuously perifused and suitable for the study of luteinizing hormone-releasing hormone (LHRH)-anterior pituitary physiology is described. Adult male Sprague-Dawley rats were decapitated and the anterior pituitaries removed, dispersed using collagenase, mixed with Biogel P2, and packed into 0.9-cm columns using sterile technique. All experiments were conducted using Krebs-Ringer-bicarbonate-glucose buffer, and a stable base line was achieved. A constant dose of LHRH (50 ng) administered several times at 1-h intervals stimulated the same quantal release of LH. LH secretion is linear in response to LHRH over the range of 1-50 nM and to rat hypothalamic extracts over a range of 1/32 to 1/2 hypothalamic equivalents, regardless of whether the extracts are administered in ascending or descending order. These results indicate that perifusion of dispersed pituitary cells provides a useful model for the study of LHRH physiology, combining the advantages of the long-term viability of pituitary cells in culture with the dynamic nature afforded by perifusion.
Animals↗
Therapeutic use of pituitary desensitization with a long-acting lhrh agonist: a potential new treatment for idiopathic precocious puberty.
A two year girl with idiopathic true precocious puberty was treated with a long-acting LHRH agonist, D-Trp6-Pro9-NEt-LHRH (LHRHa). Prior to therapy, the patient demonstrated pulsatile gonadotropin secretion during both night and day, a pubertal response to exogenous LHRH, and an elevated plasma estradiol level. After eight weeks of therapy (4 microgram/kg daily), a mean gonadotropin levels fell to the prepubertal range, there was no evidence of pulsatile discharge of gonadotropins nor any response to exogenous LHRH, and plasma estradiol levels became undetectable. No adverse drug reactions were encountered and all effects of therapy were reversed following cessation of treatment for two months. LHRH analogs may offer a new approach to the therapy of idiopathic precocious puberty and merit further study.
Child, Preschool↗