GnRH-stimulated Luteinizing Hormone Research Articles

Comparison of central precocious puberty frequency before and during COVID-19: a systematic review and meta-analysis

ObjectiveThe current systematic review and meta-analysis assessed the prevalence of central precocious puberty (CPP) throughout the novel coronavirus disease 2019 (COVID-19) pandemic.DesignA systematic review and meta-analysis were carried out following the principles outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA, 2020).Data sourcesPubMed, Embase, Web of Science, and WANFANG databases were searched from January 1, 2019, to March 30, 2023.Eligibility criteria for selecting studies(1) children and adolescents ≤ 15 years; (2) studies with the outcome of frequency of central precocious puberty, measured prior to and throughout the COVID-19 pandemic; (3) a novel CPP diagnosis was created depending on all of the following criteria: girls with a chronological age < 8 years and boys with a chronological age < 9 years at the onset of symptoms, basal luteinizing hormone (LH) levels > 0.3 UI/L, and/or GnRH-stimulated peak LH levels > 5 IU/L.Data extraction and synthesisThe process of extracting data and evaluating the likelihood of bias was carried out by two independent reviewers. The data were pooled employing the generic inverse-variance method and presented as mean differences (MDs) with 95% CIs. The evaluation of heterogeneity was conducted employing the Cochran Q statistic, and the degree of heterogeneity was measured employing the I2 statistic.ResultsThis meta-analysis included 17 studies. In contrast to the same period prior to the COVID-19 pandemic, the occurrence of CPP elevated (OR = 2.57; 95% CI, 1.85–3.56). Moreover, body mass index standard deviation score (BMI SDS) differences between CPP patients prior to COVID-19 and throughout the pandemic follow-up was 0.12 (95% CI − 0.01 to 0.25 P = 0.06).ConclusionOverall, CPP frequency significantly elevated throughout the COVID-19 pandemic. Given the restricted number of cohort investigations in this meta-analysis, additional research may be conducted on larger groups of children in order to establish a correlation between the observed rise in precocious puberty and specific pathogenic factors.

Unstimulated Luteinizing Hormone for Assessment of Suppression during Treatment of Central Precocious Puberty with 6-Month Subcutaneous Leuprolide Acetate: Correlations with Clinical Response

Introduction: Phase 3 trial of 6-month subcutaneous leuprolide acetate (SC-LA) in children with central precocious puberty (CPP) demonstrated efficacy and safety. The aims of this secondary analysis were to evaluate unstimulated luteinizing hormone (LH) as efficacy measure, assess clinical suppression metrics, and present biochemical and clinical data for subgroups not achieving hormone suppression. Methods: Sixty-two children with treatment-naïve CPP received 2 doses of 45 mg SC-LA at 24-week intervals. Unstimulated and GnRH-stimulated LH, E2, and T concentrations were measured. Clinical measures included bone age (BA) and predicted adult height (PAH). Results: Eighty-four percentage and 86% of children achieved unstimulated LH <1 IU/L at weeks 24 and 48, respectively. Of 8 children not achieving unstimulated LH <1 IU/L at week 24 that completed the study, all showed a lack of pubertal stage progression and stable/decreased BA to chronological age ratio (BA/CA). Received operating characteristic (ROC) analyses suggested unstimulated LH is a good diagnostic predictor of GnRH-stimulated LH <4 IU/L at weeks 24 and 48 (AUC = 0.88). Across all children, mean BA/CA improved from 1.4 (screening) to 1.3 (week 48) and mean PAH increased by 3 cm. Of 7 girls not achieving stimulated LH <4 IU/L at week 24, all achieved E2 <10 pg/mL, showed a lack of pubertal stage progression, and had stable or decreased BA/CA by week 48. Additionally, 6/7 had increased PAH by week 48 and 4 had unstimulated LH <1 IU/L. Conclusion: Unstimulated LH has value as an efficacy measure and concentrations <1 IU/L may be an adequate surrogate of treatment response in children with CPP. All children who completed the study had evidence of pubertal suppression.

The influence of body composition on the response to dynamic stimulation of the endocrine pituitary-testis axis

BackgroundTestosterone treatment is generally not recommended in men with obesity induced low serum testosterone. However, distinguishing this condition from overt testosterone deficiency in men with obesity where treatment should be initiated is a diagnostic challenge and tools to differentiate these conditions are scarce but could be of important clinical relevance.ObjectivesTo investigate the association between body composition and dynamic responses of the pituitary-testis axis in men.MethodsSingle-center cross-sectional study including 112 healthy men. Participants went through a full biochemical assessment of the pituitary-testis axis, and dynamic stimulatory tests of luteinizing hormone (LH) secretion (gonadotropin-releasing hormone (GnRH)-test) and testosterone secretion (choriogonadotropin (hCG)-test). A subset (N = 78) further had a DXA-scan performed.ResultsA higher body mass index (BMI) was associated with lower basal serum LH (BU = −0.44, 95% CI: −0.88–−0.01, p = 0.04). The GnRH-stimulated LH increase was not significantly associated with BMI (BU = −0.10, 95% CI: −0.72–0.51, p = 0.74). Furthermore, a high BMI was associated with low basal testosterone (BU −0.02, 95% CI: −0.03–−0.02, p < 0.001), and free testosterone (BU −15.0, 95% CI: −19.9–−10.0, p < 0.001) and men with overweight and obesity had significantly lower testosterone (9%, p = 0.003 and 24%, p < 0.001) and free testosterone (25%, p = 0.006 and 50%, p < 0.001) concentrations compared to men with normal weight. The HCG-stimulated testosterone increase was significantly less dependent on BMI compared to the influence of BMI on basal testosterone concentrations (p = 0.04 for the interaction).ConclusionsDynamic sex hormone responses following pituitary-testis axis stimulation were less dependent on BMI, compared to the influence of BMI on basal hormone concentrations and could potentially assist clinical decision making in patients with obesity suspected of testosterone deficiency.

THU195 6-Month Subcutaneous Leuprolide Acetate Achieved And Maintained Hormonal And Clinical Suppression In All Weight Groups Of Children With Central Precocious Puberty

Abstract Disclosure: B.S. Miller: Consulting Fee; Self; Abbvie, Ascendis Pharma, Bristol Myers Squibb, BioMarin, Endo Pharmaceuticals, EMD Serono, Novo Nordisk, Pfizer, Tolmar Pharmaceuticals. Research Investigator; Self; Alexion, Abbvie, Aeterna Zentaris, Amicus, Lumos Pharma, Lysogene, Novo Nordisk, OPKO Health, Pfizer, Prevail Therapeutics, Sangamo Therapeutics. D. Boldt-Houle: Employee; Self; Tolmar Pharmaceuticals, Inc. S.N. Atkinson: Employee; Self; Tolmar Pharmaceuticals, Inc. Background: Childhood obesity is associated with an increased risk of central precocious puberty (CPP).1 Thus, data on whether weight status affects the treatment of children with CPP would be valuable to help clinicians ensure correct management. We present secondary analyses of hormone and height velocity (HV) data from the pivotal trial of the first small-volume, long-acting, subcutaneously administered gonadotropin-releasing hormone agonists (GnRHa) for CPP, with the goal of assessing if the study drug adequately suppresses hormones in overweight and obese children. Methods: 62 children with treatment-naïve CPP received 2 doses of 45 mg subcutaneous leuprolide acetate at 24-week intervals over the 48-week study period. The BMI percentile for children was calculated based on the Center for Disease Control growth charts, accounting for height, weight, age, and gender. Luteinizing hormone (LH) concentrations were assessed using a validated central Cobas ECLIA assay with a lower limit of detection of 0.100 IU/L. Estradiol (E2) concentrations were assessed using liquid chromatography-tandem mass spectrometry/mass spectrometry (LC-MS/MS) with a lower limit of detection of 10 pg/mL. HV was calculated as the change in height between visits/((number of weeks between visits)/52). Results: Mean GnRH-stimulated LH concentrations at screening, week 24, and week 48 were 24.5, 2.1, and 2.5 IU/L in non-overweight children, 10.5, 3.2, and 2.2 IU/L in overweight children, and 31.5, 4.8, and 1.9 IU/L in obese children, respectively. In these same groups, mean E2 concentrations at screening, week 24, and week 48 were 28.2, 10.5, and 10.3 pg/mL in non-overweight children, 17.8, 10.4, and 10.4 pg/mL in overweight children, and 25.9, 11.0, and 11.1 pg/mL in obese children, respectively. Mean HV at week 4, week 24, and week 48 was 10.2, 5.6, and 5.7 cm/year in non-overweight children, 7.7, 5.5, and 6.2 cm/year in overweight children, and 8.2, 4.9, and 6.6 cm/year in obese children, respectively. Conclusions: Subcutaneous leuprolide acetate effectively treated all overweight children without any requirement for weight-based dosing. This is consistent with results from previous studies of GnRHa efficacy in obese and normal-weight children with CPP.2 Clinicians should consider providing counseling and interventions that support healthy diets and lifestyles to children with above-normal BMI and their caregivers. References Cited 1.Liu G, Guo J, Zhang X, Lu Y, Miao J, Xue H. Obesity is a risk factor for central precocious puberty: a case-control study. BMC Pediatr. 2021;21(1):509.2. Chen M, Eugster EA. Central precocious puberty: update on diagnosis and treatment. Paediatr Drugs. 2015;17(4):273-281. Presentation: Thursday, June 15, 2023

Association of the KISS1, LIN28B, VDR and ERα gene polymorphisms with early and fast puberty in Chinese girls

Objectives To explore the association of KISS1, LIN28B, vitamin D receptor (VDR), and estrogen receptor α (ERα) gene polymorphisms and the risk of early with fast puberty (EFP) risk, and with hormone levels in EFP cases, in Chinese girls. Methods The analysis was based on the data of 141 girls with EFP and 152 girls without EFP. Clinical features were documented, and all SNP genotyping was conducted using SNaPshot method. Statistical analysis was performed to assess the association of the SNPs with EFP risk, and with hormone levels in EFP cases. Results There was a significant association between rs7759938-C polymorphism in the LIN28B gene and the risk for EFP in the recessive (TT + CT vs. CC) model (p = 0.040). Remarkably, rs5780218-delA polymorphism in the KISS1 gene and rs2234693-C polymorphism in the ERα gene were significantly associated with peak LH (luteinizing hormone) levels (p = 0.008, 0.045) and peak LH/FSH (follicle-stimulating hormone) ratio (p = 0.007, 0.006). Additionally, on 7 of the 8 variant loci the alleles associated with increased levels of both peak LH levels and peak LH/FSH ratio in EFP cases were also associated with increased CPP risk. Conclusions Our findings indicate that rs7759938-C polymorphism in the LIN28B gene might have a protective effect on EFP susceptibility. The most striking findings of this study is that, rs5780218-delA polymorphism in the KISS1 gene and rs2234693-C polymorphism in the ERα gene influenced levels of GnRH-stimulated peak LH and LH/FSH ratio, and in general CPP risk genes might also contributes to the abnormality of hormonal levels in EFP.

ODP335 Mutual Effects of Orexin and BMPs on Gonadotropin Expression by Mouse Gonadotrope LβT2 Cells

Abstract Orexins are neuropeptides that express primarily in the hypothalamus and are produced in two isoforms, orexin A and orexin B. There are two kinds of G protein coupled receptors, orexin type 1 (OX1R) and type 2 (OX2R) receptors. Orexin has been reported to have key roles on sleep-wake regulation and feeding behavior in the central nervous system, whereas its receptors are also expressed in peripheral tissues including the endocrine organs, and orexin affects the regulation of the endocrine system. In our previous experiments, we have revealed the impact of orexins on anterior pituitary functions. For instance, we reported that orexin A plays an inhibitory role in prolactin production through the suppression of endogenous bone morphogenetic protein (BMP) activity in rat pituitary lactotrope GH3 cells. It was also reported that orexin A enhances pro-opiomelanocortin (POMC) transcription by upregulating corticotropin-releasing hormone (CRH) receptor signaling and by downregulating BMP-Smad signaling in mouse corticotope AtT20 cells. However, the effects of orexin on the endocrine function regarding gonadotrope cells remain unclear. We have recently uncovered that core clock genes and BMPs have mutual effects on luteinizing hormone (LH) expression in a phase-dependent manner by mouse gonadotrope LβT2 cells. In the present study, we investigated the effect of orexin on pituitary gonadotropin expression using LβT2 cells, which express OX1R and OX2R, by focusing on the functional involvement of BMP system and clock genes. It was revealed that orexin A stimulation increased LHβ and FSHβ mRNA expression in a concentration-responsive manner in the absence of GnRH, and interestingly, GnRH co-treatment further upregulated LHβ mRNA expression in LβT2 cells. Regarding the interrelationships between the signalings of orexin and BMPs, it was also revealed that orexin A pretreatment enhanced the BMP receptor signaling detected as the Smad1/5/9 phosphorylation, indicating that orexin enables to upregulate the BMP actions in LβT2 cells. In our previous studies, we reported that several BMP ligands such as BMP-6, -7 and 15 expressed in LβT2 cells can promote gonadotropin transcription, in which BMP-6 regulates GnRH-stimulated LH expression by modulating the sensitivity to somatostatin analogs. Based on the present results, it was implied that endogenous orexin can be functionally involved in the underlying mechanisms of gonadotropin expression. Collectively, orexin enhances gonadotropin expression by regulating BMP signaling in gonadotrope cells. Here, we will also discuss functional involvement of clock genes in the regulatory system of gonadotropin secretion induced by orexin and BMPs. Presentation: No date and time listed

The GnRH Antagonist Degarelix Suppresses Gonadotropin Secretion and Pituitary Sensitivity in Midgestation Sheep Fetuses.

The specific role of gonadotropin-releasing hormone (GnRH) on brain sexual differentiation remains unclear. To investigate whether gonadotropin and, in turn, testosterone (T) secretion is regulated by GnRH during the critical period for brain differentiation in sheep fetuses, we attempted to selectively suppress pituitary-testicular activation during midgestation with the long-acting GnRH antagonist degarelix. Fetuses received subcutaneous injections of the antagonist or vehicle on day 62 of gestation. After 2 to 3 weeks we examined consequences of the intervention on baseline and GnRH-stimulated plasma luteinizing hormone (LH) and T levels. In addition, we measured the effect of degarelix-treatment on messenger RNA (mRNA) expression for the pituitary gonadotropins and key gonadal steroidogenic enzymes. Baseline and GnRH-stimulated plasma LH levels were significantly suppressed in degarelix-treated male and female fetuses compared to control values. Similarly, T concentrations were suppressed in degarelix-treated males. The percentage of LHβ-immunoreactive cells colocalizing c-fos was significantly reduced by degarelix treatment indicating that pituitary sensitivity was inhibited. Degarelix treatment also led to the significant suppression of mRNA expression coding for the pituitary gonadotropin subunits and for the gonadal enzymes involved in androgen synthesis. These findings demonstrate that pharmacologic inhibition of GnRH early in gestation results in suppression of LH secretion and deficits in the plasma T levels of male lamb fetuses. We conclude that GnRH signaling plays a pivotal role for regulating T exposure during the critical period of sheep gestation when the brain is masculinized. Thus, disturbance to gonadotropin secretion during this phase of gestation could have long-term consequence on adult sexual behaviors and fertility.

Triptorelin stimulated luteinizing hormone concentrations for diagnosing central precocious puberty: study of diagnostic accuracy.

PurposeGonadotropin-releasing hormone (GnRH) stimulation test is the gold standard for diagnosing central precocious puberty (CPP). However, intravenous GnRH is not always readily available. The aim of the present study was to evaluate the diagnostic accuracy of triptorelin-stimulated luteinizing hormone (LH) concentrations in the diagnosis of CPP among girls presenting with premature thelarche compared to the gold standard GnRH test.MethodsA prospective, case–control (CPP vs isolated premature thelarche), clinical study evaluating the diagnostic accuracy of triptorelin-stimulated LH concentrations in 60 girls with premature thelarche was performed. All girls underwent stimulation with subcutaneous triptorelin injection and intravenous GnRH in a randomized order. During the stimulation test with triptorelin, LH and FSH were measured at time 0, 30, 60, 90, 120, and 180 min after the injection. Estradiol was sampled 24 h after the injection. During the GnRH test, LH and FSH were measured at time 0, 30, 45, and 60 min. Girls with peak GnRH-stimulated LH concentrations ≥5.0 IU/L were classified as having CPP. Area under the curve (AUC) for triptorelin-stimulated LH concentrations was assessed using the receiver operating characteristic (ROC) analysis.ResultsTriptorelin-stimulated LH concentrations were significantly higher in girls who had CPP according to the GnRH test (53.3%). LH peaked at 180 min after the triptorelin injection. The highest diagnostic accuracy for CPP (AUC = 0.973, sensitivity 96.9%, specificity 89.3%) at 180 min was at a LH concentration ≥3.4 IU/L. The 24 h estradiol concentration did not improve the predictive model.ConclusionsMeasuring LH concentrations 180 min after triptorelin injection with a cut-off value of ≥3.4 IU/L demonstrated a high diagnostic accuracy compared to the GnRH test. Thus, stimulation with triptorelin can be used as a reliable alternative for diagnosing CPP in girls with premature thelarche.

Short-term efficacy of 1-month and 3-month gonadotropin-releasing hormone agonist depots in girls with central precocious puberty.

PurposeGonadotropin-releasing hormone agonist (GnRHa) has been the mainstay of central precocious puberty (CPP) treatment for decades, but few reports have compared the efficacy of 1-month and 3-month depot GnRHa formulations. This study investigates the short-term efficacy of 1-month and 3-month GnRHa depots in girls with CPP.MethodsOverall, 150 girls with CPP were included in a retrospective review of medical records. Subjects in group 1 (n=105) were treated with 1-month GnRHa depots for ≥12 months, and those in group 2 (n=45) were treated with 1-month GnRHa depots for 6 months followed by 3-month GnRHa depots for ≥6 months. Anthropometric and biochemical data were compared between the groups at 3-time points (after 0, 6, and 12 months of GnRHa treatment).ResultsDemographic and clinical characteristics did not differ between the groups at baseline or after 6 months of GnRHa treatment. After 12 months of GnRHa treatment, patients in the both groups showed no difference in bone age (BA), chronological age (CA), BA–CA difference, height standard deviation score (SDS) for CA and BA, or body mass index SDS for CA and BA. The sexual maturity rate of the breast was prepubertal at 12 months in most of subjects. GnRH-stimulated luteinizing hormone (LH) level was suppressed during GnRHa treatment in both groups at 6 and 12 months, although the LH level in group 2 was higher than that in group 1.ConclusionsTreating CPP with a 3-month GnRHa depot showed short-term efficacy comparable to that with a 1-month depot in anthropometric parameters and pubertal suppression.

Using kisspeptin to predict pubertal outcomes for youth with pubertal delay

CONTEXT The management of youth with delayed puberty is hampered by difficulty in predicting who will eventually progress through puberty and who will fail to attain adult reproductive endocrine function. The neuropeptide kisspeptin, which stimulates gonadotropin-releasing hormone (GnRH) release, can be used to probe the integrity of the reproductive endocrine axis. OBJECTIVE We sought to determine whether responses to kisspeptin can predict outcomes for individuals with pubertal delay. DESIGN, SETTING, AND PARTICIPANTS We conducted a longitudinal cohort study in an academic medical center of 16 children (3 girls and 13 boys) with delayed or stalled puberty. INTERVENTION AND OUTCOME MEASURES Children who had undergone kisspeptin- and GnRH-stimulation tests were followed every 6 months for clinical evidence of progression through puberty. Inhibin B was measured in boys. A subset of participants underwent exome sequencing. RESULTS All participants who had responded to kisspeptin with a rise in luteinizing hormone (LH) of 0.8 mIU/mL or greater subsequently progressed through puberty (n = 8). In contrast, all participants who had exhibited LH responses to kisspeptin ≤ 0.4 mIU/mL reached age 18 years without developing physical signs of puberty (n = 8). Thus, responses to kisspeptin accurately predicted later pubertal outcomes (P = .0002). Moreover, the kisspeptin-stimulation test outperformed GnRH-stimulated LH, inhibin B, and genetic testing in predicting pubertal outcomes. CONCLUSION The kisspeptin-stimulation can assess future reproductive endocrine potential in prepubertal children and is a promising novel tool for predicting pubertal outcomes for children with delayed puberty.

β-Arrestin-dependent signaling in GnRH control of hormone secretion from goldfish gonadotrophs and somatotrophs

In goldfish, two native isoforms of gonadotropin-releasing hormone (GnRH2 and GnRH3) stimulate luteinizing hormone (LH) and growth hormone (GH) release from pituitary cells through activation of cell-surface GnRH-receptors (GnRHRs) on gonadotrophs and somatotrophs. Interestingly, GnRH2 and GnRH3 induce LH and GH release via non-identical post-receptor signal transduction pathways in a ligand- and cell-type-selective manner. In this study, we examined the involvement of β-arrestins in the control of GnRH-induced LH and GH secretion from dispersed goldfish pituitary cells. Treatment with Barbadin, which interferes with β-arrestin and β2-adaptin subunit interaction, reduced LH responses to GnRH2 and GnRH3, as well as GH responses to GnRH2; but enhanced GnRH3-induced GH secretion. Barbadin also had positive influences on basal hormone release, and basal GH release in particular, as well as basal activity of extracellular signal-regulated kinase (ERK) and GnRH-induced ERK activation. These findings indicate that β-arrestins play permissive roles in the control of GnRH-stimulated LH release. However, in somatotrophs, β-arrestins, perhaps by mediating agonist-selective endosomal trafficking of engaged GnRHRs, participate in GnRH-isoform-specific GH release responses (stimulatory and inhibitory for GnRH2-GnRHR and GnRH3-GnRHR activation, respectively). The correlative stimulatory influences of Barbadin on basal hormone release and ERK activation suggest that β-arrestins may negatively regulate basal secretion through modulation of basal ERK activity. These results provide the first direct evidence of a role for β-arrestins in hormone secretion from an untransformed primary pituitary cell model, and establish these proteins as important receptor-proximal players in mediating functional selectivity downstream of goldfish GnRHRs.

Evaluation of the influence of prenatal transportation stress on GnRH-stimulated luteinizing hormone and testosterone secretion in sexually mature Brahman bulls

Evaluation of the influence of prenatal transportation stress on GnRH-stimulated luteinizing hormone and testosterone secretion in sexually mature Brahman bulls

Hypothalamic action of phoenixin to control reproductive hormone secretion in females: importance of the orphan G protein-coupled receptor Gpr173

Sexual maturation and maintenance of reproductive function are regulated by neurohormonal communication between the hypothalamus, pituitary, and gonads (referred to as the HPG axis). Phoenixin (PNX) is a newly identified, endogenous peptide abundantly produced in the hypothalamus and shown to be an important mediator of ovarian cyclicity. However, the underlying mechanisms by which phoenixin functions within the HPG axis are unknown. Previous in vitro studies demonstrated a direct action of PNX on gonadotrophs to potentiate gonadotrophin-releasing hormone (GnRH) induced luteinizing hormone (LH) secretion. Therefore, we hypothesized that centrally derived phoenixin regulates the preovulatory LH surge required for ovarian cyclicity. We observed a significant dose-related increase in the level of plasma LH in diestrous, female rats that were given an intracerebroventricular injection of PNX compared with vehicle-treated controls. While this suggests that even under low-estrogen conditions, PNX acts centrally to stimulate the HPG axis, further characterization is contingent on the elucidation of its cognate receptor. Using the "deductive ligand receptor matching strategy," we identified the orphan G protein-coupled receptor, Gpr173, as our top candidate. In cultured pituitary cells, siRNA-targeted compromise of Gpr173 abrogated PNX's action to potentiate GnRH-stimulated LH secretion. In addition, siRNA-mediated knockdown of endogenous Gpr173, which localized to several hypothalamic sites related to reproductive function, not only significantly extended the estrous cycle but also prevented the PNX-induced LH secretion in diestrous, female rats. These studies are the first to demonstrate a functional relationship between PNX and Gpr173 in reproductive physiology and identify a potential therapeutic target for ovulatory dysfunction.

The non-steroidal mycoestrogen zeranol suppresses luteinizing hormone secretion from the anterior pituitary of cattle via the estradiol receptor GPR30 in a rapid, non-genomic manner

Picomolar concentrations of estradiol produce rapid suppression of GnRH-induced luteinizing hormone (LH) secretion from the anterior pituitary (AP) of cattle via G-protein-coupled receptor 30 (GPR30). Zeranol is a strong estrogenic metabolite derived from zearalenone, a non-steroidal mycoestrogen produced by Fusarium that induces reproductive disorders in domestic animals. The hypothesis was tested that zeranol suppresses GnRH-induced LH release from the AP of cattle via GPR30 in a rapid, non-genomic manner. The AP cells (n=15) were cultured for 3 days in steroid-free conditions and then treated them with estradiol (0.001–10nM) or zeranol (0.001–100nM) for 5min before GnRH stimulation. Pre-treatment with 0.001–0.1nM estradiol suppressed GnRH-stimulated LH secretion. Pre-treatment with zeranol at concentrations of 0.001nM (P<0.01), 0.01nM (P<0.01), 0.1nM (P<0.05), and 1nM (P<0.05), but not at concentrations of 10 and 100nM, also inhibited GnRH-stimulated LH secretion from AP cells. Pre-treatment for 5min with a GPR30-specific antagonist, G36, inhibited estradiol or zeranol suppression of LH secretion from cultured AP cells. Cyclic AMP measurements and quantitative PCR analyses revealed that pre-treatment with small amounts of estradiol (P<0.05) or zeranol (P<0.01) decreased cAMP, but not gene expressions of the LHα, LHβ, or FSHβ subunits in the AP cells. Hence, zeranol may suppress luteinizing hormone secretion from the AP of cattle via GPR30 in a rapid, non-genomic manner.

Advances in the etiology, diagnosis and treatment of central precocious puberty

The onset of puberty is first detected as an increase in the amplitude and frequency of pulses of gonadotropin-releasing hormone (GnRH) after a quiescent period during childhood. The reemergence of pulsatile GnRH secretion leads to increases in the secretion of the gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) by the pituitary gland, and the consequent activation of gonadal function. Early activation of the hypothalamic-pituitary-gonadal axis results in gonadotropin-dependent precocious puberty, also known as central precocious puberty (CPP), which is clinically defined by the development of secondary sexual characteristics before the age of 8 years in girls and 9 years in boys. Pubertal timing is influenced by complex interactions among genetic, nutritional, environmental, and socioeconomic factors. CPP is diagnosed on the basis of clinical signs of progressive pubertal development before the age of 8 years in girls and 9 years in boys, pubertal basal and/or GnRH-stimulated LH levels, and advanced bone age. Magnetic resonance imaging of the central nervous system is essential for establishing the CPP form as organic or idiopathic. Depot GnRH-analogues represent the first-line of therapy in CPP. Very recently, the genetic component of CPP was demonstrated by the evidence that the deficiency of the MKRN3 gene, located on long arm of chromosome 15, causes familial CPP in humans. In this current review, clinical and therapeutic aspects of the CPP will be discussed, contributing to adequate diagnosis and criterious approach of this relevant condition of pediatric endocrinology.

Expression of estradiol receptor, GPR30, in bovine anterior pituitary and effects of GPR30 agonist on GnRH-induced LH secretion

G-protein – coupled receptor 30 (GPR30) is an estradiol receptor located on the plasma membrane, and it initiates several rapid, non-genomic signaling events. GPR30 has recently been identified in rat anterior pituitary (AP); however, little is known about the role of GPR30 in controlling luteinizing hormone (LH) secretion from gonadotropes in animals. To fill this research gap, we hypothesized that GPR30 is expressed in bovine AP and mediates estradiol inhibition of gonadotropin-releasing hormone (GnRH)-induced LH release. We confirmed the expressions of GPR30 mRNA and protein by RT-PCR, western blotting, and immunohistochemistry. We cultured bovine AP cells (n=8) for 3 days in steroid-free conditions and then treated them with increasing concentrations (0.001nM, 0.01nM, 0.1nM, 1nM, and 10nM) of estradiol or a GPR30-specific agonist, G1, for 5min before GnRH stimulation. As expected, estradiol at 0.001–0.1nM inhibited the GnRH-stimulated LH secretion. However, we found also that G1 at 0.001nM was able to inhibit this secretion (P<0.05). In contrast, both estradiol and G1 at higher doses were less efficient in suppressing the GnRH-stimulated LH secretion. Neither estradiol nor G1 suppressed GnRH-stimulated follicle-stimulating hormone secretion. In separate experiments, fluorescent immunohistochemistry and immunocytochemistry revealed that approximately 50% of GPR30-positive cells express LH, and about 30% of LH-positive cells express GPR30. In conclusion, GPR30 is expressed in bovine gonadotropes and other AP cells and may partially contribute to rapid negative estradiol feedback of GnRH-induced LH secretion.

LPS-induced inflammation potentiates the IL-1β-mediated reduction of LH secretion from the anterior pituitary explants.

Acting at the level of the brain, interleukin- (IL-)1β is considered to be one of the most potent downregulators of reproduction processes during immune/inflammatory challenge. IL-1β suppresses gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus resulting in the inhibition of the luteinizing hormone (LH) release from the anterior pituitary (AP). However, the presence of IL-1β receptors in the AP suggests the possible direct action of this cytokine on LH secretion. The study was designed to determine the effect of IL-1β on the LH secretion from the AP explants collected from saline and LPS-treated ewes in the follicular phase. It was found that IL-1β suppressed (P ≤ 0.01) GnRH-stimulated LH release and LHβ gene expression in AP explants in both groups. However, IL-1β action was more potent in the explants collected from LPS-treated animals. Pituitaries from LPS-treated animals were characterized by increased (P ≤ 0.01) IL-1 type I receptor and decreased (P ≤ 0.01) GnRH receptor gene expression level compared to the saline-treated group. IL-1β also affected the GnRH-R gene expression in explants collected from LPS-treated animals. Our results show that direct action of IL-1β on the pituitary gonadotropes could be one of the reasons of the reproductive processes disorders accompanying an inflammatory state.

Ovarian stimulation with FSH in the rat reduces proestrous GnRH-dependent LH secretion through a dual mechanism: Inhibition of LH synthesis and release

Administration of human follicle-stimulating hormone (hFSH) to female rats during diestrus phase attenuates the spontaneous luteinizing hormone (LH) surge in proestrous afternoon. The inhibition of LH secretion is associated with a decreased pituitary LH content in intact, but not in ovariectomized rats injected with 25 μg estradiol benzoate (EB). This suggests that the mechanism of action of the putative non-steroidal ovarian bioactive FSH-dependent gonadodotropin surge attenuating factor (GnSAF) might, in addition, involve a reduction in LH synthesis. The present experiments studied, in proestrous pituitaries, the effects of different doses of hFSH, with or without EB on: (i) basal and GnRH-stimulated LH release and GnRH self-priming, (ii) LHβ mRNA values, and (iii) LH content. Results showed that bioactive GnSAF reduced mainly GnRH self-priming, but also GnRH-stimulated LH secretion and pituitary LH content in a dose-dependent manner. GnSAF had no effect on basal LH secretion or pituitary LHβ mRNA values. EB increased pituitary sensitivity to GnRH in controls, and overcame the inhibitory effects of GnSAF after low doses of hFSH but not after 10 IU of hFSH. In contrast with the sensitizing action of EB on LH secretion, EB had no effect on pituitary LHβ mRNA content or LH protein. It is concluded that the putative GnSAF blunted the LH surge by reducing LH synthesis at post-transcriptional level and antagonizing the GnRH-dependent LH secretion and the sensitizing effect of estradiol to GnRH.

Proteasome Regulation of Dynamic Transcription Factor Occupancy on the GnRH-Stimulated Luteinizing Hormone β-Subunit Promoter

GnRH is the main modulator of LH secretion and transcription of the LH subunit genes in pituitary gonadotropes. The LHbeta gene is preferentially transcribed during pulsatile GnRH stimuli of one pulse/30 min and is thus carefully controlled by specific signaling pathways and transcription factors. We now show that GnRH-stimulated LHbeta transcription is also influenced by the ubiquitin-proteasome system. GnRH-stimulated activity of an LHbeta reporter gene was prevented by proteasome inhibitors MG-132 and lactacystin. Inhibition was not rescued by overexpression of two key transcription factors for LHbeta, early growth response-1 (Egr-1) and steroidogenic factor-1 (SF-1). Increased endogenous LHbeta transcription after GnRH treatment was also prevented by MG-132, as measured by primary transcript assays. To investigate possible mechanisms of LHbeta transcriptional inhibition by proteasome blockade, we employed chromatin immunoprecipitation to measure LHbeta promoter occupancy by transcription factors. Without GnRH, binding was low and unorganized. With GnRH, Egr-1 and SF-1 associations were stimulated, cyclic, and coincidental, with a period of approximately 30 min. MG-132 disrupted GnRH-induced Egr-1 and SF-1 binding and prevented phosphorylated RNA polymerase II association with the LHbeta promoter. Egr-1, but not SF-1, protein was induced by GnRH and accumulated with MG-132. Egr-1 and SF-1 were ubiquitinated in gonadotropes and ubiquitinated forms of these factors associated with the LHbeta promoter, suggesting their degradation may be key for LHbeta proteasome-dependent transcription. Together, these results demonstrate that degradation via the proteasome is vital to GnRH-stimulated LHbeta expression, and this occurs in part by allowing proper transcription factor associations with the LHbeta promoter.

Leptin increases L-type Ca2+ channel expression and GnRH-stimulated LH release in LβT2 gonadotropes

Leptin, a mediator of long-term regulation of energy balance, has been implicated in the release of adenohypophyseal gonadotropins by regulating gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus. However, a direct effect of leptin on hormone release from gonadotropes remains virtually unexplored. In the current report, we assessed the long-term (48 h) actions of leptin on voltage-gated channel activity and luteinizing hormone (LH) production in mouse pituitary gonadotrope LbetaT2 cells. Electrophysiological recordings showed that leptin treatment significantly increased whole-cell patch-clamp Ba(2+) current through L-type Ca(2+) channels. Quantitative RT-PCR analysis revealed increased levels of L-type (alpha(1D)) Ca(2+) channel mRNA. Likewise, radioimmunoassays using specific antibodies provided evidence that leptin alone had no effect on LH release but did enhance GnRH-induced secretion of the hormone. Leptin had no apparent effects on LH gene transcription in absence of GnRH, as measured by transient transfection assays using a LH promoter-reporter gene and real-time RT-PCR. These observations suggest that leptin might affect LH release by acting directly on the gonadotropes, favoring hormone production by enhancing responsiveness to GnRH as a result of increased Ca(2+) channel expression.