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At least 55 records · Page 3Linked to original sources
PubMed1989

Comparison of immunoreactive gonadotropin-releasing hormone and human chorionic gonadotropin in term placentas from normal women and those with insulin-dependent and gestational diabetes.

We measured prohormone gonadotropin-releasing hormone (high-molecular-weight gonadotropin-releasing hormone), gonadotropin-releasing hormone and human chorionic gonadotropin concentrations in term placentas from normal women and those with insulin-dependent and gestational diabetes. The placental immunoreactive gonadotropin-releasing hormone levels were significantly higher in normal tissues than in tissues from insulin-dependent and gestational diabetes (p less than 0.01). When compared with diabetic placental extracts, normal tissue also had more stored prohormone immunoreactive gonadotropin-releasing hormone. Whereas there were no consistent differences in placental human chorionic gonadotropin concentrations in normal tissues and tissues from insulin-dependent and gestational diabetes, there was a significant correlation between gonadotropin-releasing hormone and human chorionic gonadotropin concentrations in normal samples (r = 0.57, p less than 0.05), which was abolished when the diabetic tissue was included in the analysis. These data suggest that differences in high-molecular-weight gonadotropin-releasing hormone and gonadotropin-releasing hormone concentrations in term placentas from normal versus diabetic mothers may be due to enhanced processing of the prohormone and increased release of the decapeptide in diabetic pregnancy.

Cesarean Section↗
PubMed1997

Novel independent and synergistic regulation of gonadotropin-alpha subunit gene by luteinizing hormone/human choriogonadotropin and gonadotropin releasing hormone in the alphaT3-1 gonadotrope cells.

The alphaT3-1 cells are immortalized anterior pituitary gonadotropes which express gonadotropin-alpha subunit gene. These cells contain receptors for gonadotropin releasing hormone (GnRH) as well as for luteinizing hormone (LH) which can also bind human choriogonadotropin (hCG). Like GnRH, LH and hCG can upregulate the expression of gonadotropin-alpha subunit gene. While 0.1-1.0 ng/ml hCG can upregulate, higher concentrations have no effect. However, these higher hCG concentrations can act in a synergistic manner with GnRH to increase the steady state mRNA and protein levels of gonadotropin-alpha subunit. The synergism between hCG and GnRH was mimicked by LH but not by other hormones in the glycoprotein hormone family or alpha or beta subunits of hCG, suggesting that the synergism is hormone specific and requires the conformation of native hormone. The hCG induced increase in gonadotropin-alpha subunit mRNA levels was due to a significant increase in the half-life of gonadotropin-alpha subunit transcripts from 7.8 +/- 1.0 h in the controls to 16.5 +/- 3.8 h after treatment with hCG. The GnRH induced increase in gonadotropin-alpha subunit mRNA levels was due to both a significant increase in the half-life to 26.2 +/- 3.0 h as well as a significant increase in the transcription rate of the gene (159.0 +/- 7.7% of the control). A greater increase in gonadotropin-alpha subunit mRNA levels following a combined treatment with GnRH and hCG was due to a further increase in half-life to 37.6 +/- 3.1 h as well as a greater increase in the transcription rate of the gene (295.1 +/- 24.2% of the control) as compared to the treatment with GnRH alone. In summary, we conclude that LH and hCG can independently and synergistically act with GnRH to increase the expression of gonadotropin-alpha subunit gene by transcriptional as well as by post-transcriptional mechanisms in alphaT3-1 cells. These effects may be important for the increase of LH levels during the preovulatory surge.

Animals↗
PubMed2004

Expression and regulation of luteinizing hormone/human chorionic gonadotropin receptors in ovarian cancer and its correlation to human chorionic gonadotropin-doxorubicin sensitivity.

OBJECTIVE: Ovarian cancer cell lines and tissues express gonadotropin receptors. Conjugation of cytostatics to ligands of these receptors may increase the specificity of cytotoxic drugs. STUDY DESIGN: Toxicity of doxorubicin-human chorionic gonadotropin conjugates was determined in 4 ovarian cancer cell lines. Expression and regulation of luteinizing hormone/human chorionic gonadotropin receptors were analyzed before and after treatment with human chorionic gonadotropin, epidermal growth factor, and 8-bromo-cyclic adenosine monophosphate with a nested reverse transcriptase-polymerase chain reaction approach. RESULTS: Toxicity of human chorionic gonadotropin-doxorubicin conjugates was increased compared with unconjugated doxorubicin in OVCAR-3 cells. However, drug conjugates failed to demonstrate increased toxicity in other cell lines, especially after preincubation with human chorionic gonadotropin. All cell lines expressed luteinizing hormone/human chorionic gonadotropin receptors. Receptor expression in OVCAR-3 cells was not effected by human chorionic gonadotropin, endothelial growth factor, or 8-bromo-cyclic adenosine monophosphate treatment. In other cell lines, receptor expression was down-regulated by these agents. CONCLUSION: Cytotoxic activity of doxorubicin was increased specifically by conjugation to human chorionic gonadotropin. However, the regulation of luteinizing hormone/human chorionic gonadotropin receptor expression and other compounds may reduce the drug-uptake of the conjugates.

Antibiotics, Antineoplastic↗
PubMed1996

More basic isoforms of serum gonadotropins during gonadotropin-releasing hormone agonist therapy in pubertal children.

An acute challenge of exogenous GnRH elicits rapidly increased serum gonadotropin levels with qualitative changes to more basic isoforms of both FSH and LH. Chronic GnRH agonist therapy suppresses endogenous gonadotropins, and the serum levels of FSH and LH are low and fairly constant. A possible qualitative change in the gonadotropins during GnRH agonist therapy was investigated by determination of the median charge of the gonadotropin isoforms before and during therapy in 18 pubertal children. Two different GnRH agonists were studied: buserelin, given intranasally or as a sc implant for 1.5-34 months to five girls, aged 7-10 yr, and for 5-6 months to two boys, aged 11-13 yr; and triptorelin, administered as a depot preparation for 3-6 months to four girls, aged 9-12.5 yr, and for 1-24 months to seven boys, aged 10.5-12 yr. FSH and LH in serum and eluates after electrophoresis in 0.10% agarose suspension were measured with sandwich fluoroimmunoassays. The mean serum FSH and LH levels decreased significantly (P < 0.05) in girls during triptorelin therapy, whereas only the FSH level decreased (P < 0.05) in the boys. There were no significant (P > 0.05) changes in serum gonadotropin levels during buserelin therapy. All of the children had more basic serum isoforms of LH, and all but one had more basic forms of FSH during the GnRH agonist treatments. In a girl who had more basic gonadotropin isoforms after treatment with triptorelin for 2 and 6 months, a GnRH challenge elicited the release of still more basic isoforms. The changes in mean median charge to more basic gonadotropin isoforms were highly significant for both busereline (P < 0.01) and triptorelin (P < 0.001) treatment. An increased (P < 0.001) degree of charge heterogeneity was observed for FSH after triptorelin therapy. These findings show that there is a qualitative change in the isoforms of both FSH and LH in serum during GnRH agonist therapy in pubertal children. The changes in charge to more basic gonadotropin isoforms most likely reflect a direct effect at the pituitary level, leading to the synthesis and/or selective release of less sialylated and sulfated isoforms of the gonadotropins. The observed qualitative changes in the gonadotropin isoforms in these pubertal children may be part of the clinical effects of GnRH agonist therapy, leading to an arrest or regression of puberty.

Adolescent↗
PubMed1984

Human chorionic gonadotropin testing. Changing testicular response in infants with microphallus and gonadotropin deficiency.

The evaluation of microphallus often includes human chorionic gonadotropin (HCG) stimulation to evaluate testicular androgen production. The response in testosterone secretion after five days of stimulation with chorionic gonadotropin is abnormal in patients with either primary testicular defects or gonadotropin deficiency. The testes of gonadotropin-deficient children do respond if the chorionic gonadotropin therapy is continued for six weeks. The current study reports a normal response to the short course (five days) of chorionic gonadotropin therapy in two 2-month-old patients with XY chromosomes with microphallus whose clinical course and repeated testing at age 3 or 4 years indicated gonadotropin deficiency. The normal response in the neonatal period is probably the result of maternal chorionic gonadotropin priming of the fetal testes in utero. These results indicate that HCG testing is an unreliable method for identifying gonadotropin deficiency in the neonatal period.

Abnormalities, Multiple↗
PubMed1996

Gonadotropins and ovarian gonadotropin receptors during the perimenopausal transition period.

As an early sign of perimenopause, the menstrual cycles become irregular. Associated with this irregularity, serum gonadotropin levels increase. There are studies correlating these changes to ovarian follicular morphology and number, but no reports are available, to our knowledge, correlating the increases in gonadotropin levels to respective cellular receptors. In fact, the regulation of gonadotropin receptors is poorly understood in the human. The action of gonadotropins on gonadal function is mediated through specific binding of the hormones to receptors located on the surface of target cells followed by activation of intracellular second messenger systems. In the ovary, the target cells for FSH are granulosa cells of ovarian follicles, while the action of LH is mediated through binding of the ligand to theca, granulosa and luteal cells. The cell-surface receptors for gonadotropins are located respectively on these cell types. The molecular nature of FSH receptors and LH receptors has been characterized in many species, and their structure is well-known both on the protein and nucleic acid level. Despite the vast amount of studies in rodents, there is limited information available on the regulation of gonadotropin receptors in the human. In a recent study, serum LH and FSH levels were correlated to respective receptor levels in ovarian tissue in order to better understand gonadotropin action and the physiology of the menopause in the human. High serum gonadotropin levels in perimenopause suggested the existence of low ovarian gonadotropin receptor levels. In most patients who are still experiencing cyclic menstrual bleeding no FSH receptors were detected possibly due to severe disturbances in follicular FSH receptor synthesis prior to ovarian follicle exhaustion.

Climacteric↗
PubMed2004

Comparison of clinical outcome and costs with CC + gonadotropins and gnrha + gonadotropins during Ivf/ICSI cycles.

OBJECTIVE: To compare clinical outcome and costs of CC + gonadotropins with GnRHa + gonadotropins during IVF/ICSI cycles. MATERIALS AND METHODS: Clinical outcome and expenses of 382 CC + gonadotropin and 964 GnRHa + gonadotropin cycles were compared. Medication costs were calculated on the basis of the mean number of ampoules and the proportion of various gonadotropins. Costs per clinical pregnancy were calculated on the basis of expenses and clinical pregnancy rates. RESULTS: Women in the CC + gonadotropin group were younger, and had fewer follicles, oocytes, embryos, and embryos transferred. Clinical pregnancy rates were higher in the GnRHa group (35.9 % vs 26.2%, p < 0.001). More ampoules of gonadotropins were used in the GnRHa group (24.0 +/- 0.3 vs 20.0 +/- 0.5, p < 0.001). Medication costs per cycle were higher in the GnRHa group (US dollars 357 vs 248). Expenses per pregnancy however were lower in the GnRHa group (USdollars 4197 vs 5335 with IVF; USdollars 5590 vs 7244 with ICSI). When different age subgroups with similar baseline characteristics and stimulation parameters were compared, pregnancy rates were significantly higher in the GnRHa groups. Medication cost per cycle was higher in the GnRHa subgroups, and the expense per pregnancy was lower with GnRHa protocol. CONCLUSIONS: Cost per cycle is higher with GnRHa + gonadotropin. However, because of the better performance of the GnRHa + gonadotropin stimulation, the cumulative costs are reduced by the time a clinical pregnancy is achieved.

Adult↗
PubMed1986

Hormonal therapy of cryptorchidism. A randomized, double-blind study comparing human chorionic gonadotropin and gonadotropin-releasing hormone.

We conducted a randomized, double-blind study comparing intranasal gonadotropin-releasing hormone (1.2 mg per day for 28 days) with parenteral human chorionic gonadotropin (3300 IU per week for four weeks) in the treatment of cryptorchidism in 33 boys one to five years old (29 with unilateral and 4 with bilateral cryptorchidism). Testicular descent into the scrotum occurred in 3 of the 16 patients (19 percent) treated with gonadotropin-releasing hormone and in 1 of the 17 (6 percent) treated with human chorionic gonadotropin (P = 0.23). The mean luteinizing hormone and testosterone levels were similar in both groups before treatment. During treatment, the testosterone levels were significantly increased in both groups, but higher levels occurred in the group treated with human chorionic gonadotropin (P less than 0.05). In a parallel (but uncontrolled) study of five boys with retractile testes (defined as a nonscrotal testis that could be manipulated into the bottom of the scrotum) who were originally excluded from the main protocol but were treated with the same regimen of human chorionic gonadotropin, descent into the scrotum occurred in all patients. We conclude that hormonal therapy with either gonadotropin-releasing hormone or human chorionic gonadotropin is, in most cases, ineffective in promoting testicular descent of true cryptorchid testes. However, short-term treatment with human chorionic gonadotropin is very effective in producing descent of retractile testes. These results suggest that the wide discrepancies in apparent efficacy in previous trials of hormonal therapy of cryptorchidism may have been due to inclusion in those studies of various proportions of patients with retractile testes.

Administration, Intranasal↗
PubMed1989

Gonadotropin and alpha-subunit responses to chronic gonadotropin-releasing hormone analog administration in patients with glycoprotein hormone-secreting pituitary tumors.

Pituitary tumors secreting intact glycoprotein hormones (LH, FSH, and TSH) and/or alpha-subunit are being increasingly recognized. Because chronic administration of GnRH analogs decreases gonadotropin secretion in normal subjects, we investigated gonadotropin and alpha-subunit responses to chronic GnRH analog administration in five men with glycoprotein hormone-secreting pituitary tumors. Two patients (patients A and B) received the GnRH agonist analog (D-Trp6-Pro9-NEt-LHRH) for 4 weeks as a daily sc dose (8 micrograms/kg.day). In both, secretion of LH and/or alpha-subunit increased markedly. Subsequently, three patients received a higher analog dose (32 micrograms/kg.day) for a longer duration (8 weeks). One patient with a LH- and FSH-secreting tumor (patient C) had a highly significant (P less than 0.001) fall in serum LH and FSH concentrations; however, alpha-subunit secretion increased. During a subsequent study, when this patient received a lower dose (8 micrograms/kg.day) for 8 weeks, gonadotropin suppression also occurred. In two additional patients who received this dose (32 micrograms/kg.day), it had a persistent agonist effect on FSH beta (patient D) and alpha-subunit secretion (patient E). A marked increase in alpha-subunit secretion occurred in all five patients, regardless of whether basal serum alpha-subunit concentrations were elevated. These patients received the GnRH analog at doses 2-8 times greater than those that suppress gonadotropin secretion in normal men. Serum LH and FSH concentrations decreased in only one patient with a gonadotropin-secreting adenoma. The serum LH and FSH responses to acute GnRH stimulation did not predict the gonadotropin responses to chronic GnRH analog administration. Thus, gonadotropin and alpha-subunit production by most pituitary adenomas is augmented during chronic GnRH analog administration, consistent with defective GnRH desensitization in the adenomatous tissue. Despite the heterogeneous gonadotropin responses to the GnRH analog in these patients, serum alpha-subunit levels increased in all patients, indicating dissociation in the secretion of intact gonadotropins and alpha-subunit.

Adenoma↗
PubMed1985

Estradiol potentiation of gonadotropin-releasing hormone responsiveness in the anterior pituitary is mediated by an increase in gonadotropin-releasing hormone receptors.

In order to investigate the mechanism by which 17 beta-estradiol potentiates the action of gonadotropin-releasing hormone on the anterior pituitary in vitro, cultured pituitary cells from immature female rats were used as the model system. Cultures exposed to estradiol at concentrations ranging from 10(-10) to 10(-6) mol/L exhibited a significant augmentation of luteinizing hormone release in response to a 4-hour gonadotropin-releasing hormone (10 mumol/L) challenge at a dose of 10(-9) mol/L compared to that of control cultures. The estradiol augmentation of luteinizing hormone release was also dependent on the duration of estradiol exposure. When these cultures were incubated with tritium-labeled L-leucine, an increase in incorporation of radiolabeled amino acid into total proteins greater than that in controls was observed. A parallel stimulatory effect of estradiol on iodine 125-labeled D-Ala6 gonadotropin-releasing hormone binding was observed. Cultures incubated with estradiol at different concentrations and various lengths of time showed a significant increase in gonadotropin-releasing hormone binding capacity and this increase was abrogated by cycloheximide. Analysis of the binding data showed that the increase in gonadotropin-releasing hormone binding activity was due to a change in the number of gonadotropin-releasing hormone binding sites rather than a change in the affinity. These results suggest that (1) estradiol treatment increases the number of pituitary receptors for gonadotropin-releasing hormone, (2) the augmentary effect of estradiol on luteinizing hormone release at the pituitary level might be mediated, at least in part, by the increase in the number of binding sites of gonadotropin-releasing hormone, and (3) new protein synthesis may be involved in estradiol-mediated gonadotropin-releasing hormone receptor induction.

Animals↗
PubMed2000

Mutations of gonadotropins and gonadotropin receptors: elucidating the physiology and pathophysiology of pituitary-gonadal function.

The recent unraveling of structures of genes for the gonadotropin subunits and gonadotropin receptors has provided reproductive endocrinologists with new tools to study normal and pathological functions of the hypothalamic-pituitary-gonadal axis. Rare inactivating mutations that produce distinctive phenotypes of isolated LH or FSH deficiency have been discovered in gonadotropin subunit genes. In addition, there is a common polymorphism in the LHbeta subunit gene with possible clinical significance as a contributing factor to pathologies of LH-dependent gonadal functions. Both activating and inactivating mutations have been detected in the gonadotropin receptor genes, a larger number in the LH receptor gene, but so far only a few in the gene for the FSH receptor. These mutations corroborate and extend our knowledge of clinical consequences of gonadotropin resistance and inappropriate gonadotropin action. The information obtained from human mutations has been complemented by animal models with disrupted or inappropriately activated gonadotropin ligand or receptor genes. These clinical and experimental genetic disease models form a powerful tool for exploring the physiology and pathophysiology of gonadotropin function and provide an excellent example of the power of molecular biological approaches in the study of pathogenesis of diseases.

Amino Acid Sequence↗
PubMed1988

The efficacy of every-other-day administration of gonadotropin-releasing hormone in women with hypothalamic amenorrhea: gonadotropin-releasing hormone treatment can induce clomiphene responsiveness.

The efficacy of every-other-day gonadotropin-releasing hormone administration was investigated in clomiphene-human chorionic gonadotropin (hCG) resistant, anovulatory women with hypogonadotropism or normogonadotropism. One hundred micrograms of gonadotropin-releasing hormone was injected intramuscularly three times a week for four weeks (one course). Ten of 11 hypogonadotropic patients responded to clomiphene or clomiphene-hCG after one to three courses of gonadotropin-releasing hormone treatment. Once the patients were converted to clomiphene responsiveness, ovulatory response continued without additional treatment, and all four patients who desired pregnancy conceived. Among eight normogonadotropic women, four with amenorrhea of one year or less became clomiphene-hCG responders after one or two courses of gonadotropin-releasing hormone treatment. They were subsequently treated with gonadotropin-releasing hormone after every one or two ovulatory cycles. One of the four women who desired to be pregnant conceived. We conclude that intramuscular gonadotropin-releasing hormone treatment is effective in inducing responsiveness to clomiphene, especially in hypogonadotropic anovulatory women. In normogonadotropic women, gonadotropin-releasing hormone treatment may be useful in those who have been amenorrheic for less than a year.

Amenorrhea↗
PubMed1990

Gonadotropin-releasing hormone deficiency in men: diagnosis and treatment with exogenous gonadotropin-releasing hormone.

Idiopathic hypogonadotropic hypogonadism in men is the result of absent or abnormal secretion of gonadotropin-releasing hormone, which prevents pubertal development. Isolated gonadotropin-releasing hormone deficiency is clinically and neuroendocrinologically heterogeneous, largely because of variation in the degree of gonadotropin-releasing hormone deficiency. Treatment with pulsatile gonadotropin-releasing hormone results in normal pubertal changes and virilization. Such treatment has been uniformly successful in normalizing release of gonadotropins and secretion of testosterone. Improvement in secondary sex characteristics and induction of spermatogenesis have been achieved in most patients. Eight of nine patients desiring induction of fertility were able to father a child. Use of pulsatile gonadotropin-releasing hormone presents a powerful model in which to examine regulation of gonadotropin secretion and the role of hypothalamic gonadotropin-releasing hormone in control of the male reproductive axis.

Adolescent↗
PubMed2001

Regulation of gonadotropin subunit gene transcription by gonadotropin-releasing hormone: measurement of primary transcript ribonucleic acids by quantitative reverse transcription-polymerase chain reaction assays.

GnRH regulates the synthesis and secretion of the pituitary gonadotropins LH and FSH. One of the actions of GnRH on the gonadotropin subunit genes (alpha, LHbeta, and FSHbeta) is the regulation of transcription [messenger RNA (mRNA) synthesis]. Gonadotropin subunit transcription rates increase after gonadectomy and following exogenous GnRH pulses. However, prior studies of subunit mRNA synthesis were limited by the available methodology that did not allow simultaneous measurement of gene transcription and mature mRNA concentrations. The purpose of the current studies was to: 1) develop a reliable and sensitive method for assessing transcription rates by measuring gonadotropin subunit primary transcript RNAs (PT, RNA before intron splicing); 2) investigate the PT responses to GnRH following castration or exogenous GnRH pulses; 3) characterize the half-disappearance time for the three PT species after GnRH withdrawal; and 4) correlate changes in PT concentration with steady-state gonadotropin subunit mRNA levels measured in the same pituitary RNA samples. Using oligonucleotide primers that flanked intron-exon boundaries, quantitative RT-PCR assays for each subunit PT species were developed. These assays require only ng amounts of RNA to measure each gonadotropin subunit PT and allow us to measure both PTs and steady-state mRNAs in a single pituitary RNA sample. Primary transcript concentrations in intact male rats showed a relative abundance of alpha > LHbeta congruent with FSHbeta, similar to the relationship found previously for mRNA levels. Additionally, each PT species was only 1-2% as abundant as the corresponding mRNA. One week after castration, gonadotropin subunit PT levels were increased (alpha: 3-fold, LHbeta: 6-fold, and FSHbeta: 3-fold) in a pattern similar to subunit mRNAs. Administration of GnRH antagonist to 7-day castrate male rats resulted in a rapid decline in PT concentrations with a half-disappearance time of 2.7 h for LHbeta and 0.8 h for FSHbeta, significantly faster than earlier measurements of the half-disappearance time for mature mRNA. Finally, in a GnRH-deficient male rat model, LHbeta and FSHbeta PT concentrations increased 4- to 6-fold 5 min after a GnRH pulse and then declined toward levels seen in control animals. These data indicate that the effects of GnRH on subunit gene transcription are an important determinant of gonadotropin regulation. The appearance and disappearance of PT RNA occurs more rapidly than changes in mature mRNA. Additionally, concentrations are elevated in long term castrates, and following an exogenous GnRH pulse the transcriptional burst is rapid and brief.

Animals↗
PubMed1994

High efficacy of gonadotropin or pulsatile gonadotropin-releasing hormone treatment in hypogonadotropic hypogonadal men.

In order to determine the efficacy of gonadotropin and gonadotropin-releasing hormone (GnRH) therapy in hypogonadotropic hypogonadal men, we performed a retrospective clinical analysis in the outpatient clinic of a University Center for Reproductive Medicine, Twenty-six men with either hypothalamic (idiopathic hypogonadotropic hypogonadism, N = 6; Kallmann syndrome, N = 8) or pituitary disorders (N = 12) were treated with gonadotropins or GnRH for induction of spermatogenesis in 33 treatment cycles and, additionally, for induction of pregnancy in the female partner in 18 out of 33 cases (12 of 26 patients). Patients were treated with a combination of 1000-2500 IE of human chorionic gonadotropin twice per week and 75-150 IE human menopausal gonadotropin three times per week intramuscularly or subcutaneously. Alternatively, GnRH was administered at doses of 5-20 micrograms every 120 min subcutaneously to men with hypothalamic disorders. Treatment lasted until sperm appeared in the ejaculate or pregnancy was induced. During therapy, testosterone levels increased into the normal range. Total testicular volumes increased significantly during therapy despite low initial testicular volumes and histories of maldescended testes. Sperm appeared in the ejaculate in 30 of 33 treated patients. Pregnancies occurred in 15 out of 18 cases even with sperm counts far below the normal range. We could not detect differences in the efficacy of gonadotropin or GnRH treatment in hypogonadotropic hypogonadism. Thus, we conclude that both gonadotropin and pulsatile GnRH therapy are most effective in the induction of spermatogenesis and pregnancies in hypogonadotropic hypogonadal men, despite maldescended testes, low initial testicular volumes or sperm concentrations below the normal limit.

Adult↗
PubMed2006

Interactions of gonadotropin-releasing hormone (GnRH) and gonadotropin-inhibitory hormone (GnIH) in birds and mammals.

Gonadotropin-releasing hormone (GnRH) regulates secretion of both of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone. Thus, it is a key hormone for vertebrate reproduction. GnRH was considered to be unusual among hypothalamic neuropeptides in that it appeared to have no direct antagonist, although some neurochemicals and peripheral hormones (opiates, GABA, gonadal steroids, inhibin) can modulate gonadotropin release to a degree. Five years ago, a vertebrate hypothalamic neuropeptide that inhibited pituitary gonadotropin release in a dose-dependent manner was discovered in quail by Tsutsui et al. (2000. Biochem Biophys Res Commun 275:661-667). We now know that this inhibitory peptide, named gonadotropin-inhibitory hormone, or GnIH, is a regulator of gonadotropin release in vitro and in vivo. Its discovery has opened the door to an entirely new line of research within the realm of reproductive biology. In our collaborative studies, we have begun to elucidate the manner in which GnIH interacts with GnRH to time release of gonadotropins and thus time reproductive activity in birds and mammals. This paper reviews the distribution of GnIH in songbirds relative to GnRHs, and our findings on its modes of action in vitro and in vivo, based on laboratory and field studies. These data are simultaneously compared with our findings in mammals, highlighting how the use of different model species within different vertebrate classes can be a useful approach to identify the conserved actions of this novel neuropeptide, along with its potential importance to vertebrate reproduction.

Animals↗
PubMed1984

Successful induction of ovulation and conception with pulsatile intravenous administration of human menopausal gonadotropins in anovulatory infertile women resistant to clomiphene and pulsatile gonadotropin-releasing hormone therapy.

Gonadotropins are released in a pulsatile fashion at a frequency of between 1 and 2 hours in the follicular phase of the menstrual cycle. Human menopausal gonadotropins are usually administered intramuscularly. We evaluated the gonadal response to intravenous human menopausal gonadotropins administered in a pulsatile fashion over nine treatment cycles in three anovulatory infertile women. Human menopausal gonadotropin pulses in doses up to 12 IU follicle-stimulating hormone at frequencies between 2 to 3 hours over 3 to 17 days resulted in ovulation in five cycles with one pregnancy being conceived. In the ovulatory cycles (5,000 to 10,000 IU of human chorionic gonadotropin was used to induce ovulation), the 17 beta-plasma estradiol level was 961 +/- 128 versus 326 +/- 95 pg/ml (mean +/- SEM) in the anovulatory cycles (p = 0.015). The dose of human menopausal gonadotropins (in ampules of Pergonal, 75 IU of follicle-stimulating hormone and 75 IU of luteinizing hormone) in the intravenous cycles needed to induce ovulation was 12.3 +/- 1.4 versus 20.4 +/- 0.9 for intramuscular cycles (n = 80 in 23 women, p = 0.008). Treatment was well tolerated and without complications. We are continuing to explore the use of this apparently more efficient mode of administering human menopausal gonadotropins to anovulatory patients resistant to other techniques of ovulation induction therapy.

Adult↗