How to pause fertility.

Prolactin suppresses the ovarian cycles of lactating mice by directly repressing the activity of a cell population known as kisspeptin neurons.

Neuroendocrine regulation of reproduction by GnRH neurons: multidisciplinary studies using a small fish brain model.

After the discovery of GnRH, GnRH neurons have been considered to represent the final common pathway for the neural control of reproduction. There is now compelling data in mammals that two populations of kisspeptin neurons constitute two different systems to control the episodic and surge release of GnRH/LH for the control of different aspects of reproduction, follicular development and ovulation. However, accumulating evidence indicates that kisspeptin neurons in non-mammalian species do not serve as a regulator of reproduction, and the non-mammalian species are believed to show only surge release of GnRH to trigger ovulation. Therefore, the GnRH neurons in non-mammalian species may offer simpler models for the study of their functions in neuroendocrine regulation of reproduction, especially ovulation. Our research group has taken advantage of many unique technical advantages of small fish brain for the study of anatomy and physiology of GnRH neurons, which underlie regular ovulatory cycles during the breeding season. Here, recent advances in multidisciplinary study of GnRH neurons are reviewed, with a focus on studies using small teleost fish models.

Effects of undernutrition and low energy availability on reproductive functions and their underlying neuroendocrine mechanisms.

It has been well established that undernutrition and low energy availability disturb female reproductive functions in humans and many animal species. These reproductive dysfunctions are mainly caused by alterations of some hypothalamic factors, and consequent reduction of gonadotrophin-releasing hormone (GnRH) secretion. Evidence from literature suggests that increased activity of orexigenic factors and decreased activity of anorexigenic/satiety-related factors in undernourished conditions attenuate GnRH secretion in an integrated manner. Likewise, the activity of kisspeptin neurons, which is a potent stimulator of GnRH, is also reduced in undernourished conditions. In addition, it has been suggested that gonadotrophin-inhibitory hormone, which has anti-GnRH and gonadotrophic effects, may be involved in reproductive dysfunctions under several kinds of stress conditions. It should be remembered that these alterations, i.e., promotion of feeding behavior and temporary suppression of reproductive functions, are induced to prioritize the survival of individual over that of species, and that improvements in metabolic and nutritional conditions should be considered with the highest priority.

Invited review: Translating kisspeptin and neurokinin B biology into new therapies for reproductive health.

The reproductive neuropeptide kisspeptin has emerged as the master regulator of mammalian reproduction due to its key roles in the initiation of puberty and the control of fertility. Alongside the tachykinin neurokinin B and the endogenous opioid dynorphin, these peptides are central to the hormonal control of reproduction. Building on the expanding body of experimental animal models, interest has flourished with human studies revealing that kisspeptin administration stimulates physiological reproductive hormone secretion in both healthy men and women, as well as patients with common reproductive disorders. In addition, emerging therapeutic roles based on neurokinin B for the management of menopausal flushing, endometriosis and uterine fibroids are increasingly recognised. In this review, we focus on kisspeptin and neurokinin B and their potential application as novel clinical strategies for the management of reproductive disorders.

Stress, kisspeptin, and functional hypothalamic amenorrhea.

Functional hypothalamic amenorrhea (FHA) is the most common cause of secondary amenorrhea in women of reproductive age. FHA is predominantly caused by stress, decreased caloric intake, excessive exercise, or a combination thereof. These physical, psychological, and metabolic stressors cause aberration in the pulsatile release of gonadotropin-releasing hormone (GnRH) and subsequently impair function of the hypothalamic-pituitary-ovarian (HPO) axis. Various neurotransmitters acting in the central nervous system are involved in control of the HPO axis and of these, kisspeptin is one of the most important. Corticotropin-releasing hormone (CRH), also inhibits the pulsatile secretion of GnRH and also acts as an intermediary between stress factors and the reproductive system. One of the main ongoing concerns in patients with FHA is chronic hypoestrogenism, a condition, which is associated with sexual dysfunction and infertility. It may also lead to osteoporosis, and predispose to neurodegenerative and cardiovascular diseases. Treatment of FHA requires the elimination of causative factors, however, making the necessary lifestyle changes is not always easy to initiate and maintain. Broadening our knowledge of the complex neural mechanisms regulating reproductive function in which kisspeptin plays a key role can help in the development of new treatment options such as the potential of kisspeptin receptor agonists for patients with FHA.

Kisspeptin in the Prediction of Pregnancy Complications.

Kisspeptin and its receptor are central to reproductive health acting as key regulators of the reproductive endocrine axis in humans. Kisspeptin is most widely recognised as a regulator of gonadotrophin releasing hormone (GnRH) neuronal function. However, recent evidence has demonstrated that kisspeptin and its receptor also play a fundamental role during pregnancy in the regulation of placentation. Kisspeptin is abundantly expressed in syncytiotrophoblasts, and its receptor in both cyto- and syncytio-trophoblasts. Circulating levels of kisspeptin rise dramatically during healthy pregnancy, which have been proposed as having potential as a biomarker of placental function. Indeed, alterations in kisspeptin levels are associated with an increased risk of adverse maternal and foetal complications. This review summarises data evaluating kisspeptin's role as a putative biomarker of pregnancy complications including miscarriage, ectopic pregnancy (EP), preterm birth (PTB), foetal growth restriction (FGR), hypertensive disorders of pregnancy (HDP), pre-eclampsia (PE), gestational diabetes mellitus (GDM), and gestational trophoblastic disease (GTD).

Neuroendocrine mechanisms of reproductive dysfunctions in undernourished condition.

It is well known that undernourished conditions disturb female reproductive functions in many species, including humans. These alterations are mainly caused by a reduction in gonadotrophin-releasing hormone (GnRH) secretion from the hypothalamus. Evidence from the literature suggests that some hypothalamic factors play pivotal roles in the coordination of reproductive functions and energy homeostasis in response to environmental cues and internal nutritional status. Generally, anorexigenic/satiety-related factors, such as leptin, alpha-melanocyte-stimulating hormone, and proopiomelanocortin, promote GnRH secretion, whereas orexigenic factors, such as neuropeptide Y, agouti-related protein, orexin, and ghrelin, attenuate GnRH secretion. Conversely, gonadotrophin-inhibitory hormone, which exerts anti-GnRH and gonadotrophic effects, promotes feeding behavior in many species. In addition, the activity of kisspeptin, which is a potent stimulator of GnRH, is reduced by undernourished conditions. Under normal nutritional conditions, these factors are coordinated to maintain both feeding behavior and reproductive functions. However, in undernourished conditions their activity levels are markedly altered to promote feeding behavior and temporarily suppress reproductive functions, in order to prioritize the survival of the individual over that of the species.

Mathematical models in GnRH research.

Mathematical modelling is an indispensable tool in modern biosciences, enabling quantitative analysis and integration of biological data, transparent formulation of our understanding of complex biological systems, and efficient experimental design based on model predictions. This review article provides an overview of the impact that mathematical models had on GnRH research. Indeed, over the last 20 years mathematical modelling has been used to describe and explore the physiology of the GnRH neuron, the mechanisms underlying GnRH pulsatile secretion, and GnRH signalling to the pituitary. Importantly, these models have contributed to GnRH research via novel hypotheses and predictions regarding the bursting behaviour of the GnRH neuron, the role of kisspeptin neurons in the emergence of pulsatile GnRH dynamics, and the decoding of GnRH signals by biochemical signalling networks. We envisage that with the advent of novel experimental technologies, mathematical modelling will have an even greater role to play in our endeavour to understand the complex spatiotemporal dynamics underlying the reproductive neuroendocrine system.

Kisspeptins and Glucose Homeostasis in Pregnancy: Implications for Gestational Diabetes Mellitus-a Review Article.

Gestational diabetes mellitus (GDM) is becoming an increasingly common complication of pregnancy with the global rise of obesity. The precise pathophysiological mechanisms underpinning GDM are yet to be fully elucidated. Kisspeptin, a peptide encoded by the KISS1 gene, is mainly expressed by placental syncytiotrophoblasts during pregnancy. It is an essential ligand for kisspeptin 1 receptor (KISS1R), which is expressed by both the villous and invasive extravillous cytotrophoblast cells. Circulatory kisspeptins rise dramatically in the second and third trimester of pregnancy coinciding with the period of peak insulin resistance. Kisspeptins stimulate glucose-dependent insulin secretion and decreased plasma levels inversely correlate with markers of insulin resistance. Additionally, kisspeptins play a critical role in the regulation of appetite, energy utilisation and glucose homeostasis. GDM pregnancies have been associated with low circulatory kisspeptins, despite higher placental kisspeptin and KISS1R expression. This review evaluates the role of kisspeptin in insulin secretion, resistance and regulation of appetite as well as its implications in GDM.

Emerging roles for kisspeptin in metabolism.

Kisspeptin, a neuropeptide hormone, has been firmly established as a key regulator of the hypothalamic-pituitary-gonadal axis and mammalian reproductive behaviour. In recent years, a growing body of evidence has emerged suggesting a role for kisspeptin in regulating metabolic processes. This data suggest that kisspeptin exerts its metabolic effects indirectly via gonadal hormones and/or directly via the kisspeptin receptor in the brain, pancreas and brown adipose tissue. Kisspeptin receptor knockout studies indicate that kisspeptin may play sexually dimorphic roles in the physiological regulation of energy expenditure, food intake and body weight. Some, but not all, in vitro work demonstrates positive effects on glucose-stimulated insulin secretion, which is more marked at higher kisspeptin concentrations. Acute and chronic in vivo rodent, non-human primate and human studies reveal enhancement of glucose-stimulated insulin secretion in response to pharmacological doses of kisspeptin. Although significant progress has been made in elucidating the metabolic effects of kisspeptin, further mechanistic work and translational studies are required to address unanswered questions and establish the metabolic effects of kisspeptin in diverse human populations (including women, people with obesity and people with diabetes).

Hypothalamic Kisspeptin Neurons and the Control of Homeostasis.

Hypothalamic kisspeptin (Kiss1) neurons provide indispensable excitatory transmission to gonadotropin-releasing hormone (GnRH) neurons for the coordinated release of gonadotropins, estrous cyclicity, and ovulation. But maintaining reproductive functions is metabolically demanding so there must be a coordination with multiple homeostatic functions, and it is apparent that Kiss1 neurons play that role. There are 2 distinct populations of hypothalamic Kiss1 neurons, namely arcuate nucleus (Kiss1ARH) neurons and anteroventral periventricular and periventricular nucleus (Kiss1AVPV/PeN) neurons in rodents, both of which excite GnRH neurons via kisspeptin release but are differentially regulated by ovarian steroids. Estradiol (E2) increases the expression of kisspeptin in Kiss1AVPV/PeN neurons but decreases its expression in Kiss1ARH neurons. Also, Kiss1ARH neurons coexpress glutamate and Kiss1AVPV/PeN neurons coexpress gamma aminobutyric acid (GABA), both of which are upregulated by E2 in females. Also, Kiss1ARH neurons express critical metabolic hormone receptors, and these neurons are excited by insulin and leptin during the fed state. Moreover, Kiss1ARH neurons project to and excite the anorexigenic proopiomelanocortin neurons but inhibit the orexigenic neuropeptide Y/Agouti-related peptide neurons, highlighting their role in regulating feeding behavior. Kiss1ARH and Kiss1AVPV/PeN neurons also project to the preautonomic paraventricular nucleus (satiety) neurons and the dorsomedial nucleus (energy expenditure) neurons to differentially regulate their function via glutamate and GABA release, respectively. Therefore, this review will address not only how Kiss1 neurons govern GnRH release, but how they control other homeostatic functions through their peptidergic, glutamatergic and GABAergic synaptic connections, providing further evidence that Kiss1 neurons are the key neurons coordinating energy states with reproduction.

Kisspeptin signaling and nNOS neurons in the VMHvl modulate lordosis behavior but not mate preference in female mice.

It was recently shown that kisspeptin neurons in the anteroventral periventricular area (AVPV) orchestrate female sexual behavior, including lordosis behavior and mate preference. A potential target of AVPV kisspeptin signaling could be neurons expressing the neuronal form of nitric oxide synthase (nNOS) in the ventrolateral part of the ventromedial hypothalamus (VMHvl). Therefore, in the present study, we further refined the role of the VHMvl in female sexual behavior. Adult female mice received a bilateral cannula aimed at the VMHvl. A single injection with kisspeptin (Kp-10) or SNAP/BAY, a nitric oxide donor, significantly increased lordosis, whereas the nNOS inhibitor l-NAME decreased it. None of these drugs affected mate preference. Interestingly, administration of GnRH into the VMHvl had no effect on lordosis or mate preference. To determine whether the stimulatory effect of Kp-10 on lordosis was specific to the VMHvl, an additional group of females received Kp-10 directly into the paraventricular nucleus (PVN). No effect was found on lordosis and mate preference. These results suggest that kisspeptin most likely modulates lordosis behavior through nNOS neurons in the VMHvl whereas mate preference is modulated by kisspeptin through a separate neuronal circuit not including the VMHvl.

Effect of anti-Müllerian hormone on the regulation of pituitary gonadotropin subunit expression: roles of kisspeptin and its receptors in gonadotroph LßT2 cells.

Anti-Müllerian hormone (AMH) is primarily produced by ovarian granulosa cells and contributes to follicle development. AMH is also produced in other tissues, including the brain and pituitary; however, its roles in these tissues are not well understood. In this study, we examined the effect of AMH on pituitary gonadotrophs. We detected AMH and AMH receptor type 2 expression in LßT2 cells. In these cells, the expression of FSHß- but not α- and LHß-subunits increased significantly as the concentration of AMH increased. LßT2 cells expressed Kiss-1 and Kiss-1R. AMH stimulation resulted in decreases in both Kiss-1 and Kiss-1R. The siRNA-mediated knockdown of Kiss-1 in LßT2 cells did not alter the basal expression levels of α-, LHß-, and FSHß-subunits. In LßT2 cells overexpressing Kiss-1R, exogenous kisspeptin stimulation significantly increased the expression of all three gonadotropin subunits. However, kisspeptin-induced increases in these subunits were almost completely eliminated in the presence of AMH. In contrast, GnRH-induced increases in the three gonadotropin subunits were not modulated by AMH. Our observations suggested that AMH acts on pituitary gonadotrophs and induces FSHß-subunit expression with concomitant decreases in Kiss-1 and Kiss-1R gene expression. Kisspeptin, but not GnRH-induced gonadotropin subunit expression, was inhibited by AMH, suggesting that it functions in association with the kisspeptin/Kiss-1R system in gonadotrophs.

The role of makorin ring finger protein-3, kisspeptin, and neurokinin B in the physiology of minipuberty.

BACKGROUND: There is no data regarding the interrelationships of circulating Makorin Ring Finger Protein-3 (MKRN3), Kisspeptin (KISS1), and Neurokinin B (NKB) concentrations during minipuberty in humans. OBJECTIVE: To determine temporal changes in circulating concentrations of MKRN3, KISS1, NKB, and gonadotropins and investigate interrelationships between them in healthy full-term (FT) and preterm (PT) infants during minipuberty period. METHODS: A prospective study of 6-month follow-up performed. Eighty-seven healthy newborns, 48 FT (19 boys/29 girls), and 39 PT (21 boys/18 girls) (gestational age 31-37 weeks), were included. Blood samples were taken at 7 days (D7), 2 months (M2), and 6 months (M6) of age. Serum MKRN3, KISS1, NKB, LH, FSH, total testosterone (TT), and estradiol (E2) concentrations were measured. RESULTS: Seventy infants completed the study. MKRN3, KISS1, and NKB concentrations were similar in FT girls and boys. PT boys and girls also had similar concentrations of MKRN3, KISS1, and NKB. FT babies had significantly higher NKB concentrations than PT babies at D7, M2, and M6. MKRN3 and KISS1 concentrations do not differ between FT and PT babies. A strong positive correlation was found between MKRN3 and KISS1 at each time point and in all groups. FSH, LH, TT/E2 concentrations decrease while those of MKRN3 and KISS1 have a trend to increase toward the end of minipuberty. No correlation was detected between gonadotropins and MKRN3, KISS1, NKB concentrations. CONCLUSION: Strong positive correlation demonstrated between KISS1 and MKRN3 suggests that interrelationship between molecules controlling minipuberty is not similar to those at puberty.

Evidence that synaptic plasticity of glutamatergic inputs onto KNDy neurones during the ovine follicular phase is dependent on increasing levels of oestradiol.

Neurones in the arcuate nucleus co-expressing kisspeptin, neurokinin B (NKB) and dynorphin (KNDy) play a critical role in the control of gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH) secretion. In sheep, KNDy neurones mediate both steroid-negative- and -positive-feedback during pulsatile and preovulatory surge secretions of GnRH/LH, respectively. In addition, KNDy neurones receive glutamatergic inputs expressing vGlut2, a glutamate transporter that serves as a marker for those terminals, from both KNDy neurones and other populations of glutamatergic neurones. Previous work reported higher numbers of vGlut2-positive axonal inputs onto KNDy neurones during the LH surge than in luteal phase ewes. In the present study, we further examined the effects of the ovarian steroids progesterone (P) and oestradiol (E2 ) on glutamatergic inputs to KNDy neurones. Ovariectomised (OVX) ewes received either no further treatment (OVX) or steroid treatments that mimicked the luteal phase (low E2  + P), and early (low E2 ) or late follicular (high E2 ) phases of the oestrous cycle (n = 4 or 5 per group). Brain sections were processed for triple-label immunofluorescent detection of NKB/vGlut2/synaptophysin and analysed using confocal microscopy. We found higher numbers of vGlut2 inputs onto KNDy neurones in high E2 compared to the other three treatment groups. These results suggest that synaptic plasticity of glutamatergic inputs onto KNDy neurones during the ovine follicular phase depend on increasing levels of E2 required for the preovulatory GnRH/surge. These synaptic changes likely contribute to the positive-feedback action of oestrogen on GnRH/LH secretion and thus the generation of the preovulatory surge in the sheep.

Short-term changes and correlations of plasma spexin, kisspeptin, and galanin levels after laparoscopic sleeve gastrectomy.

PURPOSE: To determine the circulating levels of spexin, kisspeptin, galanin, and the correlations between these peptides after laparoscopic sleeve gastrectomy (LSG). METHODS: The plasma levels of the spexin, kisspeptin, and galanin and metabolic parameters (body mass index, weight loss, % excess weight loss, body fat, fasting glucose, HbA1C, and cholesterol levels) were measured (baseline, 1 month, and 3 months) and correlated in thirty adult individuals with obesity (22 female and 8 male) after LSG. RESULTS: The body mass index (BMI), body fat, fasting glucose, total and low-density lipoprotein cholesterol decreased, while high-density lipoprotein cholesterol and % EWL (excess weight loss) increased at 3 months after surgery. The plasma spexin levels increased at 3 months, kisspeptin levels increased at 1 month and stabilized afterward, and galanin levels decreased at 3 months after LSG. Significant correlations were found between metabolic parameters with spexin, kisspeptin, and galanin. In addition, spexin and kisspeptin were negatively correlated with galanin, while spexin was positively correlated with kisspeptin. CONCLUSIONS: The biochemical data reveal evidence that LSG causes an increase in the levels of spexin, and kisspeptin and a decrease in galanin levels. Our findings, therefore, suggest a possible interaction between these novel peptides, which have potential roles in obesity and glucose metabolism.

Leptin and inflammatory factors play a synergistic role in the regulation of reproduction in male mice through hypothalamic kisspeptin-mediated energy balance.

BACKGROUND: Energy balance is closely related to reproductive function, wherein hypothalamic kisspeptin mediates regulation of the energy balance. However, the central mechanism of kisspeptin in the regulation of male reproductive function under different energy balance states is unclear. Here, high-fat diet (HFD) and exercise were used to change the energy balance to explore the role of leptin and inflammation in the regulation of kisspeptin and the hypothalamic-pituitary-testis (HPT) axis. METHODS: Four-week-old male C57BL/6 J mice were randomly assigned to a normal control group (n = 16) or an HFD (n = 49) group. After 10 weeks of HFD feeding, obese mice were randomly divided into obesity control (n = 16), obesity moderate-load exercise (n = 16), or obesity high-load exercise (n = 17) groups. The obesity moderate-load exercise and obesity high-load exercise groups performed exercise (swimming) for 120 min/day and 120 min × 2 times/day (6 h interval), 5 days/week for 8 weeks, respectively. RESULTS: Compared to the mice in the normal group, in obese mice, the mRNA and protein expression of the leptin receptor, kiss, interleukin-10 (IL-10), and gonadotropin-releasing hormone (GnRH) decreased in the hypothalamus; serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone levels and sperm quality decreased; and serum leptin, estradiol, and tumor necrosis factor-α (TNF-α) levels and sperm apoptosis increased. Moderate- and high-load exercise effectively reduced body fat and serum leptin levels but had the opposite effects on the hypothalamus and serum IL-10 and TNF-α levels. Moderate-load exercise had anti-inflammatory effects accompanied by increased mRNA and protein expression of kiss and GnRH in the hypothalamus and increased serum FSH, LH, and testosterone levels and improved sperm quality. High-load exercise also promoted inflammation, with no significant effect on the mRNA and protein expression of kiss and GnRH in the hypothalamus, serum sex hormone level, or sperm quality. Moderate-load exercise improved leptin resistance and inflammation and reduced the inhibition of kisspeptin and the HPT axis in obese mice. The inflammatory response induced by high-load exercise may counteract the positive effect of improving leptin resistance on kisspeptin and HPT. CONCLUSION: During changes in energy balance, leptin and inflammation jointly regulate kisspeptin expression on the HPT axis.

Functions of galanin, spexin and kisspeptin in metabolism, mood and behaviour.

The bioactive peptides galanin, spexin and kisspeptin have a common ancestral origin and their pathophysiological roles are increasingly the subject of investigation. Evidence suggests that these bioactive peptides play a role in the regulation of metabolism, pancreatic ß-cell function, energy homeostasis, mood and behaviour in several species, including zebrafish, rodents and humans. Galanin signalling suppresses insulin secretion in animal models (but not in humans), is potently obesogenic and plays putative roles governing certain evolutionary behaviours and mood modulation. Spexin decreases insulin secretion and has potent anorectic, analgesic, anxiolytic and antidepressive-like effects in animal models. Kisspeptin modulates glucose-stimulated insulin secretion, food intake and/or energy expenditure in animal models and humans. Furthermore, kisspeptin is implicated in the control of reproductive behaviour in animals, modulation of human sexual and emotional brain processing, and has antidepressive and fear-suppressing effects. In addition, galanin-like peptide is a further member of the galaninergic family that plays emerging key roles in metabolism and behaviour. Therapeutic interventions targeting galanin, spexin and/or kisspeptin signalling pathways could therefore contribute to the treatment of conditions ranging from obesity to mood disorders. However, many gaps and controversies exist, which must be addressed before the therapeutic potential of these bioactive peptides can be established.

Synthesis of Kisspeptin-Mimicking Fragments and Investigation of their Skin Anti-Aging Effects.

In recent years, a number of active materials have been developed to provide anti-aging benefits for skin and, among them, peptides have been considered the most promising candidate due to their remarkable and long-lasting anti-wrinkle activity. Recent studies have begun to elucidate the relationship between the secretion of emotion-related hormones and skin aging. Kisspeptin, a neuropeptide encoded by the KISS1 gene, has gained attention in reproductive endocrinology since it stimulates the reproductive axis in the hypothalamus; however, the effects of Kisspeptin on skin have not been studied yet. In this study, we synthesized Kisspeptin-10 and Kisspeptin-E, which are biologically active fragments, to mimic the action of Kisspeptin. Next, we demonstrated the anti-aging effects of the Kisspeptin-mimicking fragments using UV-induced skin aging models, such as UV-induced human dermal fibroblasts (Hs68) and human skin explants. Kisspeptin-E suppressed UV-induced 11 beta-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) stimulation leading to a regulation of skin aging related genes, including type I procollagen, matrix metalloproteinases-1 (MMP-1), interleukin-6 (IL-6), and IL-8, and rescued the skin integrity. Taken together, these results suggest that Kisspeptin-E could be useful to improve UV-induced skin aging by modulating expression of stress related genes, such as 11ß-HSD1.

ERα Signaling in GHRH/Kiss1 Dual-Phenotype Neurons Plays Sex-Specific Roles in Growth and Puberty.

Gonadal steroids modulate growth hormone (GH) secretion and the pubertal growth spurt via undefined central pathways. GH-releasing hormone (GHRH) neurons express estrogen receptor α (ERα) and androgen receptor (AR), suggesting changing levels of gonadal steroids during puberty directly modulate the somatotropic axis. We generated mice with deletion of ERα in GHRH cells (GHRHΔERα), which displayed reduced body length in both sexes. Timing of puberty onset was similar in both groups, but puberty completion was delayed in GHRHΔERα females. Lack of AR in GHRH cells (GHRHΔAR mice) induced no changes in body length, but puberty completion was also delayed in females. Using a mouse model with two reporter genes, we observed that, while GHRHtdTom neurons minimally colocalize with Kiss1hrGFP in prepubertal mice, ∼30% of GHRH neurons coexpressed both reporter genes in adult females, but not in males. Developmental analysis of Ghrh and Kiss1 expression suggested that a subpopulation of ERα neurons in the arcuate nucleus of female mice undergoes a shift in phenotype, from GHRH to Kiss1, during pubertal transition. Our findings demonstrate that direct actions of gonadal steroids in GHRH neurons modulate growth and puberty and indicate that GHRH/Kiss1 dual-phenotype neurons play a sex-specific role in the crosstalk between the somatotropic and gonadotropic axes during pubertal transition.SIGNIFICANCE STATEMENT Late maturing adolescents usually show delayed growth and bone age. At puberty, gonadal steroids have stimulatory effects on the activation of growth and reproductive axes, but the existence of gonadal steroid-sensitive neuronal crosstalk remains undefined. Moreover, the neural basis for the sex differences observed in the clinical arena is unknown. Lack of ERα in GHRH neurons disrupts growth in both sexes and causes pubertal delay in females. Deletion of androgen receptor in GHRH neurons only delayed female puberty. In adult females, not males, a subset of GHRH neurons shift phenotype to start producing Kiss1. Thus, direct estrogen action in GHRH/Kiss1 dual-phenotype neurons modulates growth and puberty and may orchestrate the sex differences in endocrine function observed during pubertal transition.