Hypothalamic-pituitary-gonadal Axis Research Articles

Precocious Puberty in Boys with NR0B1 Variants

Precocious puberty (PP) requires appropriate management to prevent short adult height, psychosocial issues, and other adverse outcomes. Genetic diagnosis potentially improves the management of PP. Pathogenic NR0B1 variants, which typically cause X-linked adrenal hypoplasia congenita, can also affect gonadal function. While boys with NR0B1 variants usually exhibit hypogonadotropic hypogonadism during adolescence, previous reports have suggested that minipuberty, a physiological transient activation of the hypothalamic–pituitary–gonadal axis during infancy, occurs in these patients and can persist beyond a typical duration. In rare cases, NR0B1 variants cause PP. PP associated with NR0B1 variants has unique features such as early onset and high serum testosterone levels that are often disproportionate to testicular size. Three underlying mechanisms have been proposed for the association between PP and NR0B1 variants: (1) adrenocorticotropic hormone (ACTH)-dependent, (2) gonadotropin-dependent, and (3) ACTH- and gonadotropin-independent mechanisms. The factors contributing to PP vary among cases. Determining the underlying mechanisms is crucial for adopting appropriate therapeutic strategies to control PP. However, as the detailed molecular networks mediating these mechanisms are largely unclear, further research is needed to pave the way for a more effective and personalized management of patients with PP associated with NR0B1 variants.

Disorders of puberty

Puberty is a critical developmental phase marking the transition from childhood to adulthood, characterised by physical, hormonal and psychological changes. Disorders of puberty can have a significant impact on a person’s growth, development, and psychological well-being. These disorders can cause precocious (early onset) or delayed (late onset) puberty and necessitate a thorough understanding of the underlying mechanisms and clinical presentation to ensure proper diagnosis and treatment. This article provides a comprehensive overview of the hypothalamic–pituitary–gonadal axis and adrenal development leading to physical changes consistent with puberty. This article outlines the physiological physical changes and pubertal milestones and discusses normal variants of puberty to help distinguish physiological from pathological conditions. It then describes the pathophysiology and causes for both precocious and delayed pubertal development, providing guidance for primary care physicians for referral to secondary care. Finally, this article aims to provide succinct guidance on relevant history and clinical findings pertinent to the topic and provides a clinical case for discussion.

Acrylamide-induced hypothalamic-pituitary-gonadal axis disruption in rats: Androgenic protective roles of apigenin by restoring testicular steroidogenesis through upregulation of 17β-HSD, CYP11A1 and CYP17A1

Acrylamide (ARL) exposure induces significant toxicity to the hypothalamic-pituitary-gonadal (HPG) axis, leading to detrimental effects on behavior, neuroendocrine functions, steroidogensis, oxidative stress, inflammation, hormonal balance, sperm quality, and histopathological integrity in rats. This study investigates the protective role of oral apigenin (API; 10 or 20 mg/kg/day for 28 days) against ARL-induced toxicity in the HPG axis of male Wistar rats. Behavioral assessments revealed that ARL exposure impaired motor coordination and balance, as evidenced by increased landing foot splay distance and gait score. ARL-induced toxicity elevated brain Tau protein levels and disrupted hypothalamic GnRH levels, both mitigated by API. ARL triggered oxidative/nitrosative stress, reducing GSH contents and increasing MDA and NO levels in brain and testicular tissues, which were reversed by API. Hormonal imbalance, marked by decreased serum testosterone, FSH, and LH levels, was corrected by API. API enhanced semen quality parameters, with elevation in sperm count concentration and the percentages of both progressive motility and individual motility. It also normalized testicular PS and PC content, enhanced testicular cellular energy and restored seminal amino acid. The repression of testicular steroidogenesis-related enzymes CYP11A1, CYP17A1, and 17β-HSD following ARL exposure was alleviated by API administration. API also mitigated the inflammatory effects of ARL by reducing the expression of p–NF–κB p65 and TNF-α in testicular tissue. Histopathological examinations showed that API reduced neuronal and testicular degeneration, improving spermatogenesis. These findings suggest that API confers significant protective effects against ARL-induced HPG axis toxicity by restoring testicular steroidogenesis through the upregulation of 17β-HSD, CYP11A1, and CYP17A1, potentially due to its antioxidant, anti-inflammatory, and neuroprotective properties.

The assessment of urinary sexual hormones within minipuberty and correlations with anthropometrics in a cohort of healthy term children.

Minipuberty follows different trends in boys and girls. Aim of our study was to explore timing and dynamics of minipuberty in healthy infants, analyzing urinary levels of sexual hormones. Moreover, we analyzed the association among HPG axis activity and linear growth, ano-genital distances (AGDs) in both sexes, and penile length in males. Longitudinal cohort study in healthy term infants from birth to 6 months of life. Clinical evaluation (anthropometrics and AGDs) and urine sampling were performed at 0 (T0), 3 (T3), and 6 (T6) months. Urine samples were analyzed for gonadotropins and sex hormones. 165 participants were involved. The growth trend of our population was regular, as were the AGDs. Urinary hormones were correlated each other's. Specifically, in boys, the correlation coefficient between urinary FSH (uFSH) and urinary LH (uLH) decreased from T0 to T6, while between urinary Testosterone (uT) and uFSH increased. In girls, correlations between uFSH and urinary Estradiol (uE) were observed at each time point. Notably, several correlations between hormones and anthropometrics and AGDs were found; the most interesting correlation was found in males within uLH and PL (at T0 ρ: 0.323, p < 0.05 and at T3 ρ: 0.371, p < 0.01), whereas in females uFSH at T0 showed negative correlations with both length and body weight percentile at T3 (ρ: -0.505, p < 0.01 and ρ: -0.478, p < 0.01, respectively). Urinary matrix has proved to be a valuable, practical, non-invasive and cheaper method for sexual hormone assessment.

Integrated transcriptomic hypothalamic-pituitary-ovarian axis network analysis reveals the role of energy availability on egg production in layers

Energy is a crucial component for maintaining egg production in layers. The hypothalamic-pituitary-ovarian (HPO) axis is an energy-sensitive functional axis for follicle development, synthesis, and secretion of reproductive hormones, and plays a key role in modulating sustained ovulation in layers. To investigate the mechanism of integrated network regulation of the HPO axis under energy fluctuation, ninety Hy-line brown layers (265-day-old, 1.92 ± 0.02 kg) were randomly divided into three groups for an 17-day experiment: a control group (Con group) fed ad libitum from days 1 to 17, an energy deprived group (ED group) that was fed ad libitum from days 1 to 12 and then underwent a fasting period from days 13 to 17 to induce a pause in laying, and a re-fed group (Rf group) that fasted for seven days (specifically, days 1 to 5, day 7, and day 9), had ad libitum access to feed on days 6 and 8, and were continuously fed from days 10 to 17. Each treatment consisted of 10 replicates with 3 birds per replicate. The study found that energy deprivation significantly decreased reproductive performance such as egg laying rate, ovarian index, number of small yellow follicles (SYF), and normal hierarchical follicles (NHIE) (P < 0.05), which recovered after refeeding, indicating the importance of energy availability for sustained ovulation in layers. In addition, estradiol (E2), estradiol/progesterone ratio (E2/P4), and luteinizing hormone (LH) displayed changes similar to follicle number, whereas follicle-stimulating hormone (FSH) exhibited a contrasting pattern. Transcriptome analysis revealed that energy deprivation downregulated genes related to energy and appetite-regulated neurotransmitter receptors and neuropeptides in the hypothalamus. These signals combined to inhibit gonadotropin-releasing hormone (GnRH) secretion and subsequently downregulated the crucial genes responsible for synthesizing gonadotropins, gonadotropin releasing hormone receptor (GnRHR), and glycoprotein hormones alpha chain (CGA). Consequently, this suppression of the hypothalamus and pituitary affected ovarian function through ovarian steroidogenesis and the extracellular matrix (ECM)-receptor interaction. These findings suggest that energy deprivation inhibits the function of the HPO axis, leading to impaired follicle development and reduced egg production and that refeeding can partially restore these indicators.

Effects of mifepristone, a model compound with anti-progestogenic activity, on the reproduction of African clawed frog (Xenopus laevis)

This is the first study on how a substance with anti-progestogenic activity affects amphibian reproduction. Mifepristone, a synthetic anti-progestin used in abortion pills, was chosen as model compound. African clawed frog (Xenopus laevis) females were exposed to four mifepristone concentrations (0.7, 9, 120, and 1380ng∙L−1) for 30 days. A control group was also included. Egg-laying during the experiment was significantly less at the highest concentration. At the experiment’s end, mifepristone-exposed and control females were randomly mated with sexually mature males. Breeding rate for females exposed to 1380ng∙L−1 mifepristone was only 50%. Histology revealed no significant changes in gonads, thyroid, or liver. Females exposed to 1380ng∙L−1 mifepristone had lower estradiol levels in plasma, lower mRNA expression of lh and fsh in brain–pituitary complex, and p450scc in ovaries. In liver, mRNA level of npr was significantly increased in females exposed to 120ng∙L−1 mifepristone. mRNA expression of mpr, erβ, dio2, and dio3 were upregulated in animals exposed to 9ng∙L−1 and 120ng∙L−1 mifepristone, whereas vtg expression was significantly downregulated in females exposed to 1380ng∙L−1 mifepristone. All these findings show that exposure to compounds with anti-progestogenic activity affects the hypothalamus–pituitary–gonad axis and decreases reproductive success.

Revisiting the specific and potentially independent role of the gonad in hormone regulation and reproductive behavior.

Gonadal sex steroid hormones are well-studied modulators of reproductive physiology and behavior. Recent behavioral endocrinology research has focused on how the brain dynamically responds to - and may even produce - sex steroids, but the gonadal tissues that primarily release these hormones receive much less attention as a potential mediator of behavioral variation. This Commentary revisits mechanisms by which the reproductive hypothalamic-pituitary-gonadal (HPG) axis can be modulated specifically at the gonadal level. These mechanisms include those that may allow the gonad to be regulated independently of the HPG axis, such as receptors for non-HPG hormones, neural inputs and local production of conventional 'neuropeptides'. Here, I highlight studies that examine variation in these gonadal mechanisms in diverse taxa, with an emphasis on recent transcriptomic work. I then outline how future work can establish functional roles of gonadal mechanisms in reproductive behavior and evaluate gonad responsiveness to environmental cues. When integrated with neural mechanisms, further investigation of gonadal hormone regulation can yield new insight into the control and evolution of steroid-mediated traits, including behavior.

ALKBH5 Reduces BMP15 mRNA Stability and Regulates Bovine Puberty Initiation Through an m6A-Dependent Pathway.

The timing of puberty significantly influences subsequent reproductive performance in cattle. N6-methyladenosine (m6A) is a key epigenetic modification involved in the regulation of pubertal onset. However, limited research has investigated alterations in m6A methylation within the hypothalamic-pituitary-ovarian (HPO) axis during the onset of puberty. In this study, combined analysis of methylated RNA immunoprecipitation sequencing (MeRIP-Seq) and RNA sequencing (RNA-seq) is used to describe the overall modification pattern of m6A in the HPO axis, while GSEA, KEGG, and GO analyses are used to describe the enrichment pathways of differentially expressed genes and differentially methylated genes. The m6A modifications of the differential genes KL, IGSF10, PAPPA2, and BMP15 and the pathways of cell adhesion molecules (CAMs), TGF-β, cell cycle, and steroid hormone synthesis may play roles in regulating the function of the HPO axis tissue during pubertal transition. Notably, BMP15's m6A modification depends on the action of the demethylase ALKBH5, which is recognized by the reader protein YTHDF2, promoting bovine granulosa cell proliferation, steroid production, and estrogen secretion. This study reveals for the first time the modification mechanism of BMP15 m6A during the initiation of bovine puberty, which will provide useful information for improving the reproductive efficiency of Chinese beef cattle.

Postnatal Dysregulation of Androgens in Extremely Preterm Male Infants.

Neurodevelopmental impairments are common among survivors of extremely preterm birth, particularly in males. Hyperactivation of the hypothalamic-pituitary-gonadal (HPG) axis has been suggested as an underlying cause, but this has been poorly investigated. Establish levels and temporal changes in circulating androgens in extremely preterm infant males. Observational cohort study analyzing cord blood serum (n = 25) and postnatal plasma (n = 13) collected from day 0 until week 11 from infant males born at 22.8-27.9 weeks gestational age. Testosterone and dihydrotestosterone (DHT) were determined using gas chromatography mass spectrometry, sex hormone-binding globulin (SHBG) with an enzyme-linked immunosorbent assay, and follicle-stimulating hormone (FSH) and luteinizing hormone (LH) with the Luminex xMAP multiplex assay. Testosterone and DHT levels were higher on day 0 (median 4.27 and 0.30 ng/mL) than in cord blood (0.15 and 0.01 ng/mL) (P < .001 for both). Levels of the hormones then declined rapidly until day 5 (median 0.16 and 0.12 ng/mL), then remained relatively constant throughout the study period. Median levels of testosterone and DHT across the whole study period were approximately 6-fold higher than reported in utero levels. FSH and LH showed similar postnatal patterns as the androgens. SHBG steadily increased over time, and, as a result, the fraction of bioavailable testosterone declined with infant postnatal age. The HPG axis is activated immediately after birth in extremely preterm infant males, resulting in an androgen pulse occurring several months earlier than during a normal pregnancy. The long-term implications of high androgen exposure during a sensitive neurodevelopmental period warrant further studies.

12212 A Rare Case Of Central Precocious Puberty In A Male Infant With Adrenal Hypoplasia Congenita

Abstract Disclosure: A. Mastoropoulou: None. A.H. Lane: None. Introduction: We describe a male with Adrenal Hypoplasia Congenita (AHC) caused by a novel mutation in NR0B1, who was noted at 9 months of age to have central precocious puberty (CPP). Clinical case: A 3 week-old full-term male presented with hypothermia and lethargy, and a 0.3 kg weight loss since birth. Labs were consistent with adrenal crisis: Na 109 mmol/L, K 10.4 mmol/L, Ca 12.2 mg/dL, glucose 43 mg/dL. He was stabilized with stress dose hydrocortisone (HC), insulin and antibiotics, and was admitted. Subsequent labs revealed cortisol 3.5 ug/dL (4.6-23), ACTH 1,123 pg/mL (7.2-63), 17OHP 181 ng/dL (&amp;lt;199), and a renin of 180 ng/mL/h (1.7-11.2) with aldosterone 14.9 ng/dL (6-179). Abdominal ultrasound was remarkable for non-visualization of the adrenal glands. The patient was discharged with HC, fludrocortisone and sodium supplementation with good tolerance and interval weight gain and normal electrolytes. Genetic testing identified a novel pathogenic c.707G&amp;gt;A [p.Trp236Ter] nonsense variant in the DNA-binding domain of NR0B1 (DAX-1). At 9 months of age, penile enlargement with prepubertal testes was noted. Testosterone was 318 ng/dL (Tanner stage I: 0-18), LH 3.2 mIU/mL (prepubertal: 0-0.3), DHEA-S 2 ug/dL (0-33), FSH 1.1 mIU/mL (prepubertal: 0-1), consistent with hypothalamic pituitary gonadal (HPG) axis activation. Given previous reports of prolonged but self-resolving “mini-puberty of infancy” in AHC, observation was initially chosen. At 12 months of age the bone age was consistent with the Greulich and Pyle 17 months standard. At 13 months of age testosterone remained elevated, therefore based on others’ reported experiences we increased HC from 8 to 15 mg/m2/day and noted a decrease in testosterone to 104 ng/dL within 5 days. HC was further increased to 18 mg/m2/day for 15 days, however testosterone increased to 270 ng/dL, therefore decision was made to treat with Lupron Depot. Conclusions: Historically, hypogonadotropic hypogonadism has been observed in 76% of adolescent patients with AHC who have alterations in NR0B1. CPP has been infrequently described in AHC, and the natural history and management of CPP in this setting is not established. CPP in AHC does not seem to correlate with any particular functional domain of DAX1, because previously reported NR0B1 variants associated with CPP, and this case’s, are dispersed across the gene. The course of our patient suggests multiple underlying mechanisms, including early HPG axis activation as well as the possibility of ACTH dependent precocious puberty. Our observations may contribute to the understanding of factors influencing normal and abnormal puberty in infants. Increased awareness of the possibility of CPP in AHC will aid clinicians in the earlier clinical and laboratory detection of this complication. Presentation: 6/1/2024

8698 Unique populations of pituitary macrophages regulate gonadotropin secretion

Abstract Disclosure: Z. Del Mundo: None. J. Ha: None. A. Zhang: None. K.D. Wiggins: None. G. De Robles: None. C. Garcia: None. N. Ujagar: None. D. Nicholas: None. Chronic inflammation disrupts hormonal balance in the Hypothalamic-Pituitary-Gonadal (HPG) axis, contributing to reproductive disorders. Despite extensive studies on immune cells in the hypothalamus and ovaries, their impact on the pituitary is largely unexplored. Our research reveals that macrophages are the primary immune population in the pituitary during homeostasis. In response to in vivo chronic lipopolysaccharide exposure in mice, a transient macrophage population emerges, associated with reproductive changes, including elevated serum testosterone, prolonged estrous cycle stage, and reduced ovarian antral follicle count. This study aims to characterize pituitary macrophages and elucidate their impact on the HPG axis. We hypothesize that pituitary macrophages change inflammatory status as a response to stimuli and, as a result, modulate gonadotropin secretion. We pinpointed differentially expressed genes (DEGs) in pituitary macrophages using scRNAseq, distinguishing them from other tissue-resident macrophages, including microglia. These DEGs include markers for macrophage activation, phagocytosis, migration, hormone synthesis, and lipid metabolism. Immunohistochemistry validated the distinctive morphology of pituitary macrophages compared to microglia. In vitro depletion of macrophages from mouse pituitaries resulted in decreased pituitary hormone secretion and decreased secretion of G-CSF, IL-9, and CXCL5. These results highlight the role of pituitary macrophages in hormonal regulation, setting the stage for future immunotherapeutic strategies to restore hormonal balance in reproductive disorders. Presentation: 6/3/2024

12333 46 XX/XY Chimerism - Positive NIPT And Post-natal Karyotype Is It Real?

Abstract Disclosure: K.L. Del Rosario: None. N. Sheriden: None. N. Vijayakanthi: None. Introduction: Non-Invasive Prenatal Testing(NIPT) using cell free fetal DNA in plasma of pregnant women has become a routine part of prenatal care in screening for fetal aneuploidies including sex chromosome abnormalities in most regions around the world. False positive results are increasingly imposing challenges in pre-natal as well as post-natal care. Case Discussion: We report a neonate born at 32+2 weeks gestation to a 42-year-old G2 P2 mother. Pregnancy was complicated by insulin dependent maternal type 2 diabetes mellitus, maternal chronic hypertension and a positive NIPT for high-risk monosomy X. Prenatal ultrasound showed male anatomy. Interestingly on physical exam after birth, the neonate had typical male external genitalia with bilateral normal male gonads. Chromosome analysis done immediately after birth revealed the presence of two cell lines: 40 of the 50 cells (80%) had a normal female 46 XX karyotype and 10 of the 50 cells (20%) had a normal male 46 XY karyotype. These findings could be due to reabsorbed twin, Klinefelter syndrome with two trisomy rescue events, maternal cell contamination or true chimerism. In addition, fluorescence in situ hybridization (FISH) analysis for X and Y probes revealed the presence of two cell lines. The first cell line (70% of the cells) had two hybridization signals for chromosome X and the second cell line (∼25% of the cells) had one hybridization signal for chromosome X and one for chromosome Y. Postnatal ultrasound showed normal testicles with no evidence of Mullerian structures. Newborn screening was negative for congenital adrenal hyperplasia (CAH). Genetics was consulted and recommended repeat chromosomal analysis, parental testing to determine sex chromosome segregation, and follow-up with pediatric endocrinology. Repeat cytogenetic testing at 2 weeks of life resulted in a normal male chromosome complement of 46,XY. Previous abnormal cytogenetics were thought to be due to maternal cell contamination. Further endocrine labs showed LH(1.16 uIU/ml) and testosterone levels ( 87 ng/dL), appropriate levels for age indicating normal Hypothalamic Pituitary Gonadal (HPG) axis and testicular Leydig cell function. Since the family was previously counseled regarding the concept of maternal cell contamination, they expressed understanding and were happy with the update of the normal karyotype result. Conclusion: False-positive results concerning for rare chimerism on NIPT can occur and should prompt a thorough history, physical exam, ultrasound studies and repeat testing to confirm its presence. Careful consideration should be taken when counseling family about the implications of these results, especially communication about gender assignment of the infant. Presentation: 6/3/2024

7438 DAX1/NR0B1 Related Adrenal Hypoplasia Congenita Without Hypogonadotropic Hypogonadism

Abstract Disclosure: R.L. Figueiredo: None. J.B. Drummond: None. A. Meireles: None. J.L. Machado: None. G. Vidigal: None. B.S. Rocha: None. Background: X-linked congenital adrenal hypoplasia (AHC) is a rare disease caused by genetic mutations in DXA1/NRB01 gene, which encodes a nuclear hormone receptor expressed in the adrenal cortex, gonads, hypothalamus and anterior pituitary gland, occurring in less than 1:12,500 live births (1,2). AHC is characterized by primary adrenal insufficiency (PAI) associated with hypogonadotropic hypogonadism (HH) and impaired spermatogenesis (oligospermia or azoospermia). Although DAX1/NR0B1 mutations can manifest with different phenotypes, HH is mostly present, which makes this present case a diagnostic challenge. Clinical case: A 23-year-old man presented with typical symptoms of adrenal insufficiency at the age of 7 (abdominal pain, dehydration, nausea, vomiting and cutaneous hyperpigmentation). Initial testing was consistent with primary adrenal failure: elevated ACTH levels (1250pg/mL, RR&amp;lt;46pg/mL) and very low serum cortisol (0.8mcg/dL, RR 3-20mcg/dL). Etiological investigation excluded autoimmune etiology (negative anti-adrenal and anti-21-hydroxylase antibodies) as well as adrenoleukodystrophy (normal very long chain fatty acid levels). Physical exam revealed normal virilization, testicular volume and penile length. The patient reported normal libido and sexual function. Hormonal evaluation showed normal total testosterone (424 and 713ng/dL, RR 165 to 753ng/dL) as well as calculated free testosterone (7.2 and 11.4ng/mL, RR&amp;gt;3.8ng/mL) levels. Abdominal CT showed signs of bilateral adrenal hypoplasia. We then proceeded to genetic testing that revealed a pathological variant c.625C&amp;gt;T:p (Gln 209*) in hemizygosity in exon 1 of the DAX 1/NR0B1 gene. This is a nonsense mutation that introduces a premature stop codon. This variant is not present on the global and Brazilian genetic databases (gnomAD and ABraOM) and has not been previously described in the literature. The patient is currently being treated for adrenal insufficiency with the lowest tolerated dose of prednisone (7.5mg/day) and fludrocortisone 0.1mg/day. Conclusion: Etiological investigation of patients with PAI is essential to understand the evolution of the disease, monitoring extra-adrenal manifestations and the possibility of genetic counseling for the family. An intact hypothalamic-pituitary gonadal axis should not preclude genetic evaluation for a DAX/NR0B1 mutation in patients with PAI and suspected AHC. Further studies will clarify if this specific mutation carries a genotype-phenotype correlation in patients with AHC without HH.

7080 Copy Number Variation (CNV) in Self-Limited Delayed Puberty (SLDP)

Abstract Disclosure: Y. Al-Sayed: None. M. Ishida: None. C.L. Hall: None. S. Howard: None. SLDP is where the onset of puberty is more than 2-2.5 standard deviations later than the population mean age and is often familial with strong genetic determinants. The reproductive axis is regulated by gonadotropin-releasing hormone (GnRH), which plays a crucial role in initiating puberty and maintaining fertility through its pulsatile secretion. Disruption in GnRH neuron development or hypothalamic function can lead to DP. UK Biobank data has identified negative health outcomes associated with SLDP including early menopause/andropause and cognitive and psychosocial disabilities. Consequently, there has been extensive research to investigate genes affecting the hypothalamic-pituitary-gonadal (HPG) axis that might be implicated in the pathogenesis of DP by our group and others which has identified sequence variation contributing to the aetiology of SLDP. However, factors beyond nucleotide variations, such as epigenetic changes and CNVs can also lead to pubertal timing disorders. Moreover, CNVs are seen in multiple individuals (n=92) from the Deciphering Developmental Disorders study (https://www.deciphergenomics.org) with a phenotype including DP (HP:0000823). We performed whole genome sequencing on 49 probands with SLDP and subsequently, analysed the data for CNV. The data was initially called, annotated, filtered then partitioned for classification of CNVs using a command-line tool that implements the ACMG guidelines to evaluate the pathogenicity of germline duplications and deletions. Using an unbiased candidate gene approach, we identified several deletions that affected 60 known/predicted dosage sensitive genes and combines with functional enrichment analysis; This approach revealed potential molecular pathways and biological processes involved in the pathogenesis of SLDP, including histone acetylation, and neural plate development. To refine our findings, we applied additional filters, including known HPG axis genes, GWAS loci associated with pubertal timing, decipher CNV tracks, and DP gene panels, to narrow down large number of rare predicted damaging CNVs and prioritize those with potential relevance to DP. Our study highlights the potential role of CNVs in DP and expands our understanding of the molecular pathways and biological processes involved in this condition, shedding light on the complex mechanisms underlying DP. Presentation: 6/2/2024

7381 Overexpression of Makorin Ring Finger Protein 3 in the Arcuate Nucleus of Postpubertal Female Mice Impacts Neurokinin B and Kisspeptin Co-Expressing Neurons

Abstract Disclosure: S.A. Roberts: None. A. Fontes: None. S. Blau: None. M. Magnuson: None. K.M. McKnight: None. M. Sena-Esteves: None. R.S. Carroll: None. U.B. Kaiser: None. Background: Makorin ring finger protein 3 (MKRN3), an upstream inhibitor of GnRH release, is an important regulator of the age of menarche. Loss-of-function mutations in MKRN3 are the most common genetic etiology of central precocious puberty. However, its potential role in delayed puberty or hypogonadism is not well defined. In mice, expression of Mkrn3 in the hypothalamic arcuate nucleus (ARC), where kisspeptin, neurokinin B and dynorphin (KNDy) co-expressing neurons are located, is high early in life and declines before pubertal onset. Neonatal hypothalamic overexpression of Mkrn3 leads to delayed puberty in female mice and decreased neurokinin B (NKB) and kisspeptin protein levels in the ARC peripubertally. Conversely, Mkrn3-deficient peripubertal mice exhibit increased NKB protein levels in the ARC. We hypothesized that Mkrn3 overexpression in the ARC of postpubertal female mice would result in suppression of the HPG axis, manifested as hypogonadotropic hypogonadism. Methods and Results: Twelve week old adult wild type female mice were injected stereotaxically into the ARC with a novel adeno-associated virus overexpressing Mkrn3 (AAV-Mkrn3-IRES-EGFP; denoted AAV-Mkrn3) or a control virus (AAV-EGFP). Mean body weight did not differ between groups post-injection. AAV-Mkrn3 injected mice spent significantly more time (62.7%) in diestrus three to six weeks post-injection compared to controls (41.3%; P&amp;lt;0.01). Eight weeks post-injection, gonad-intact females were injected with an NKB receptor (NK3R) agonist, senktide (5 nmol or 10 nmol ip). AAV-Mkrn3 mice had a decreased peak LH response twenty minutes post-injection, compared to controls (P&amp;lt;0.001) at both doses. Peak LH levels were also reduced in response to senktide (5 nmol ip) in ovariectomized and estradiol capsule replaced (OVX+E2) AAV-Mkrn3 injected females, compared to controls (P&amp;lt; 0.001). In contrast, in both gonad-intact and OVX+E2 female mice, kisspeptin-10 (1 nmol ip) resulted in similar peak serum LH levels in AAV-Mkrn3 injected mice compared to controls. Immunohistochemistry in the ARC of intact and OVX+E2 AAV-Mkrn3 injected females showed significantly decreased NKB protein expression in AAV-Mkrn3 mice compared to controls. In response to OVX, serum LH levels increased similarly between AAV-Mkrn3 and control-injected mice. LH pulsatility in OVX females, assessed over 3 hours, showed that mean basal LH levels, number of pulses, pulse amplitude and area under the curve did not differ significantly between groups. Conclusions: These findings indicate that MKRN3 can exert inhibitory effects on the reproductive axis in female mice beyond the juvenile period, which has implications as a potential therapeutic target. The blunted response to senktide, and decreased NKB protein levels in the setting of Mkrn3 overexpression, further supports the impact of Mkrn3 on the neuropeptides and/or receptors of KNDy neurons. Presentation: 6/2/2024

9228 Insulin-Like Growth Factor-1 Modulates Arcuate Kisspeptin Neuron Activity

Abstract Disclosure: J.N. Silva: None. R. Frazao: None. The kisspeptin-producing cells located at the arcuate nucleus of the hypothalamus (ARHKisspeptin) are considered the GnRH pulse generator necessary for fertility. In addition, ARHKisspeptin cells act as a metabolic sensor to control the hypothalamic-pituitary-gonadal (HPG) axis. The insulin-like growth factor-1 (IGF-1) is considered a component contributing to puberty onset and fertility. Peripherical or intracerebroventricular IGF-1 administration is sufficient to increase hypothalamic Kiss1 expression. However, whether IGF-1 acts directly on ARHKisspeptin cells to modulate the HPG axis is not known. To determine whether IGF-1 modulates ARHKisspeptin neuron activity, we used mice expressing the green fluorescent protein “humanized renilla” under the transcriptional control of the Kiss1 gene (8-10 weeks old). Fura-2 fluorescent probe was used to evaluate the state coupled or uncoupled to calcium in the face of IGF- 1 administration (0.5 μg/ml). Furthermore, whole-cell patch-clamp was employed to determine IGF-1 effects on ARHKisspeptin neuron's resting membrane potential (RMP). FURA-2 was incorporated by 64 ARHKisspeptin neurons out of 424 cells in the ARH. IGF-1 administration to the bath led to a significant increase of the intracellular calcium levels ([Ca2+]i) in 53% of ARHKisspeptin cells evaluated in male mice (34 out of 64 cells; IGF-1, 203.0 ± 26.1 nM; baseline period, 68.8 ± 9.6 nM; P&amp;lt; 0.0001). Non-responsive cells (30 out of 64 ARHKisspeptin neurons) exhibited average [Ca2+]i of 53.2 ± 6.3 nM after IGF-1 application vs 46.2 ± 5.6 nM in the baseline period (P= 0.3). Of note, IGF-1 also increased [Ca2+]i in 25% of non-kisspeptin cells in the ARH (93 out of 364 cells, IGF-1, 193.8 ± 12.4 nM; vs baseline period, 73.0 ± 5.6 nM, P&amp;lt; 0.0001). By evaluating the IGF-1 effects on ARHKisspeptin neuron’s RMP, we observed that IGF-1 tends to depolarize the RMP of 18% of cells recorded from males (4 out of 22 cells, IGF-1, -58.0 ± 3.0 mV; baseline, -64.1 ± 4.4 mV; P= 0.05), and depolarized the RMP of 44% of cells recorded from female mice (7 out of 16 cells, IGF-1, -61.1 ± 3.3 mV; baseline, -66.3 ± 2.7 mV; P= 0.002). Importantly, IGF-1-induced depolarization of ARHKisspeptin cells RMP was blocked when the recordings were performed in the presence of tetrodotoxin and ionotropic amino acid antagonists. Therefore, IGF-1-induced effects on ARHKisspeptin cells RMP depend on action potentials mediated by synaptic transmission. Our results suggest that IGF-1 indirectly modulates the activity of a large number of ARHKisspeptin neurons. Thus, situations of metabolic stress that induce changes in growth hormone secretion and, consequently, IGF-1 circulating levels, (e.g., fasting), can modulate the HPG axis through the indirect modulation of the activity of ARHKisspeptin cells. Presentation: 6/2/2024

7996 Neuroanatomic Characterization of Mouse Kisspeptin Neurons in the Bed Nucleus of the Stria Terminalis

Abstract Disclosure: S.T. Zdon: None. M.S. Silva: None. V.M. Navarro: None. Kisspeptin (Kiss1) neurons are essential for reproductive function as they are strong regulators of the hypothalamic-pituitary-gonadal axis (HPG). Mammalian Kiss1 neurons are mainly located in the hypothalamus, controlling gonadotropin-releasing hormone (GnRH) secretion, where the anteroventral periventricular nucleus (AVPV) population is morphologically and functionally sexually differentiated. Kiss1 neurons are also found in limbic areas, such as the bed nucleus of the stria terminalis (BNST). This nucleus is involved in the integration of the HPG axis with sex-dependent social behaviors and metabolic functions. However, it remains unclear whether these populations show sexually dimorphic features. The present study focused on the neuroanatomical characterization of Kiss1BNST neurons in mice on both sexes. A Kiss1cre;salsa6f mouse strain carrying the expression of tdTomato specifically in Kiss1 neurons was used to study the distribution of Kiss1BNST neurons. The BNST is divided into the anterior division of the BNST (aBNST), and a more posterior division called the principal component of the BNST (prBNST). Results indicate that male mice have significantly more Kiss1prBNST neurons than females (Male: 139.4 ± 23.32 vs. Female: 43.70 ± 5.33 neurons; **P &amp;lt; 0.01). This sex-biased distribution was absent in Kiss1aBNST neurons. Additionally, stereotaxically injecting a Cre-dependent recombinant adenovirus carrying the expression of mCherry reporter into the aBNST or prBNST in adult mice was performed to observe neuronal projections. We observed fibers from aBNST-injected Kiss1 neurons projecting widely to areas that include the AVPV, medial preoptic area (MPO), lateral preoptic area (LPO), and periventricular hypothalamic nucleus (PVH). Moreover, fibers and cell bodies from male prBNST-injected Kiss1 neurons projected to dorsal lateral BNST (dlBNST), juxta-periventricular lateral hypothalamic area (JPLH), and the posterolateral stria terminalis (STMPL). This study observed a sexual dimorphic Kiss1 neuronal population in the prBNST, with males having more Kiss1prBNST neurons present and prospective postsynaptic areas in the brain where these neurons project to, helping to aid future studies on characterizing the functional role of these neurons. Presentation: 6/1/2024

9205 Copy Number Variation (CNV) in Self-Limited Delayed Puberty (SLDP)

Abstract Disclosure: Y. Al-Sayed: None. M. Ishida: None. C.L. Hall: None. S.R. Howard: None. SLDP is where the onset of puberty is more than 2-2.5 standard deviations later than the population mean age and is often familial with strong genetic determinants. The reproductive axis is regulated by gonadotropin-releasing hormone (GnRH), which plays a crucial role in initiating puberty and maintaining fertility through its pulsatile secretion. Disruption in GnRH neuron development or hypothalamic function can lead to DP. UK Biobank data has identified negative health outcomes associated with SLDP including early menopause/andropause and cognitive and psychosocial disabilities. Consequently, there has been extensive research to investigate genes affecting the hypothalamic-pituitary-gonadal (HPG) axis that might be implicated in the pathogenesis of DP by our group and others which has identified sequence variation contributing to the aetiology of SLDP. However, factors beyond nucleotide variations, such as epigenetic changes and CNVs can also lead to pubertal timing disorders. Moreover, CNVs are seen in multiple individuals (n=92) from the Deciphering Developmental Disorders study (https://www.deciphergenomics.org) with a phenotype including DP (HP:0000823). We performed whole genome sequencing on 49 probands with SLDP and subsequently, analysed the data for CNV. The data was initially called, annotated, filtered then partitioned for classification of CNVs using a command-line tool that implements the ACMG guidelines to evaluate the pathogenicity of germline duplications and deletions. Using an unbiased candidate gene approach, we identified several deletions that affected 60 known/predicted dosage sensitive genes and combines with functional enrichment analysis; This approach revealed potential molecular pathways and biological processes involved in the pathogenesis of SLDP, including histone acetylation, and neural plate development. To refine our findings, we applied additional filters, including known HPG axis genes, GWAS loci associated with pubertal timing, decipher CNV tracks, and DP gene panels, to narrow down large number of rare predicted damaging CNVs and prioritize those with potential relevance to DP. Our study highlights the potential role of CNVs in DP and expands our understanding of the molecular pathways and biological processes involved in this condition, shedding light on the complex mechanisms underlying DP. Presentation: 6/2/2024

12427 MKRN3 Methylation Abnormalities In Patients With Pubertal Disorders

Abstract Disclosure: N.C. Grosek: None. T. Silva: None. J.C. Magnotto: None. A. Latronico: None. A.P. Canton: None. Y. Chan: None. R.S. Carroll: None. U.B. Kaiser: None. Background and Objectives: Central Precocious Puberty (CPP) is caused by early reactivation of pulsatile GnRH secretion before age 8 years in girls and 9 years in boys. Delayed puberty (DP) is defined by the absence or incomplete development of sexual characteristics by age 13 years in girls and 14 years in boys. Environmental cues affect the HPG axis and timing of puberty via epigenetic mechanisms such as DNA methylation (DNAm). Inactivating mutations in the maternally imprinted Makorin Ring Finger 3 (MKRN3) gene are the most common genetic defect associated with CPP, representing ∼9% of patients with sporadic and familial CPP. Genomic imprinting occurs through differential methylation of CpG islands at a gene promoter or enhancer region. Differentially methylated regions (DMRs) regulate genetic imprinting. We hypothesized that transcription factor binding sites (TFBS) for ZFP57 (CpG57) andNRF1 (CpGs54+55) within the islet 3.7kb upstream of MKRN3 (MRKN3 islet) may impact expression. This study aimed to analyze if aberrant MKRN3 islet DNAm changes are associated with disorders of pubertal timing. Methods and Results: Germline DNA from 2 control patients was used to analyze the MKRN3 promoter region and islet DNAm profile. Bisulfite-treated DNA was amplified by PCR with primers targeting MKRN3 promoter and islet and submitted to Sanger sequencing. All CpG islands in the promoter region were 100% methylated, but those in the MKRN3 islet were differentially methylated with ∼50-60% methylated. DNA from our CPP cohort (n=71) underwent Next-Generation Sequencing analysis of bisulfite-treated DNA of these regions to identify the DMR potentially associated with MKRN3 imprinting. The MKRN3 islet covered CpG59-CpG49. Next, samples from our CPP cohort and patients with DP (n=44) and normal pubertal timing (n=33; 45% prepubertal, 55% pubertal) underwent pyrosequencing analyses of MKRN3islet. To compare DNAm levels between controls and our cohorts at each CpG island, T-tests were used: reported as mean±SEM. In the CPP cohort, 4/11 CpGs were significantly hypomethylated compared to controls (CpGs 54, 53, 51, 50). Specifically, the NRF1 TFBS was hypomethylated compared to controls (37.8 vs 41.6 ± 1.1, p&amp;lt;0.001) and DP (41.4 vs 43.8 ± 0.83, p=0.044). In the DP group, we found no significant difference in DNAm compared to controls. But they had hypermethylation of 4/11 CpGs compared to the CPP group, including the NRF1 TFBS (CpGs 55, 53, 51,50). Neither the CPP nor DP cohorts had significant DNAm differences at the ZFP57 TFBS compared to controls. Conclusion: Our study showed hypomethylation of 4 out of 11 CpGs in MKRN3 islet, including the NRF1 TFBS, in CPP compared to control and DP groups. On the other hand, NRF1 TFBS was hypermethylated in DPP compared to CPP. Further studies are needed to determine if these alternations in methylation are associated with MKRN3 expression levels and pubertal initiation. Presentation: 6/1/2024

8388 Insulin-Like Growth Factor-1 Modulates Arcuate Kisspeptin Neuron Activity

Abstract Disclosure: J.N. Silva: None. R. Frazao: None. The kisspeptin-producing cells located at the arcuate nucleus of the hypothalamus (ARHKisspeptin) are considered the GnRH pulse generator necessary for fertility. In addition, ARHKisspeptin cells act as a metabolic sensor to control the hypothalamic-pituitary-gonadal (HPG) axis. The insulin-like growth factor-1 (IGF-1) is considered a component contributing to puberty onset and fertility. Peripherical or intracerebroventricular IGF-1 administration is sufficient to increase hypothalamic Kiss1 expression. However, whether IGF-1 acts directly on ARHKisspeptin cells to modulate the HPG axis is not known. To determine whether IGF-1 modulates ARHKisspeptin neuron activity, we used mice expressing the green fluorescent protein “humanized renilla” under the transcriptional control of the Kiss1 gene (8-10 weeks old). Fura-2 fluorescent probe was used to evaluate the state coupled or uncoupled to calcium in the face of IGF- 1 administration (0.5 μg/ml). Furthermore, whole-cell patch-clamp was employed to determine IGF-1 effects on ARHKisspeptin neuron's resting membrane potential (RMP). FURA-2 was incorporated by 64 ARHKisspeptin neurons out of 424 cells in the ARH. IGF-1 administration to the bath led to a significant increase of the intracellular calcium levels ([Ca2+]i) in 53% of ARHKisspeptin cells evaluated in male mice (34 out of 64 cells; IGF-1, 203.0 ± 26.1 nM; baseline period, 68.8 ± 9.6 nM; P&amp;lt; 0.0001). Non-responsive cells (30 out of 64 ARHKisspeptin neurons) exhibited average [Ca2+]i of 53.2 ± 6.3 nM after IGF-1 application vs 46.2 ± 5.6 nM in the baseline period (P= 0.3). Of note, IGF-1 also increased [Ca2+]i in 25% of non-kisspeptin cells in the ARH (93 out of 364 cells, IGF-1, 193.8 ± 12.4 nM; vs baseline period, 73.0 ± 5.6 nM, P&amp;lt; 0.0001). By evaluating the IGF-1 effects on ARHKisspeptin neuron’s RMP, we observed that IGF-1 tends to depolarize the RMP of 18% of cells recorded from males (4 out of 22 cells, IGF-1, -58.0 ± 3.0 mV; baseline, -64.1 ± 4.4 mV; P= 0.05), and depolarized the RMP of 44% of cells recorded from female mice (7 out of 16 cells, IGF-1, -61.1 ± 3.3 mV; baseline, -66.3 ± 2.7 mV; P= 0.002). Importantly, IGF-1-induced depolarization of ARHKisspeptin cells RMP was blocked when the recordings were performed in the presence of tetrodotoxin and ionotropic amino acid antagonists. Therefore, IGF-1-induced effects on ARHKisspeptin cells RMP depend on action potentials mediated by synaptic transmission. Our results suggest that IGF-1 indirectly modulates the activity of a large number of ARHKisspeptin neurons. Thus, situations of metabolic stress that induce changes in growth hormone secretion and, consequently, IGF-1 circulating levels, (e.g., fasting), can modulate the HPG axis through the indirect modulation of the activity of ARHKisspeptin cells. Presentation: 6/2/2024