Using Kisspeptin to Predict Pubertal Outcomes for Youth With Pubertal Delay

Delayed Puberty Including Constitutional Delay: Differential and Outcome

Constitutional delay of growth and puberty (CDGP) is the most common cause of delayed puberty in both male and female individuals. This article reviews the causes of delayed puberty focusing on CDGP, including new advances in the understanding of the genetics underpinning CDGP, a clinical approach to discriminating CDGP from other causes of delayed puberty, outcomes, as well as current and potential emerging management options.

The Emerging Therapeutic Potential of Kisspeptin and Neurokinin B

Kisspeptin (KP) and neurokinin B (NKB) are neuropeptides that govern the reproductive endocrine axis through regulating hypothalamic gonadotropin-releasing hormone (GnRH) neuronal activity and pulsatile GnRH secretion. Their critical role in reproductive health was first identified after inactivating variants in genes encoding for KP or NKB signaling were shown to result in congenital hypogonadotropic hypogonadism and a failure of pubertal development. Over the past 2 decades since their discovery, a wealth of evidence from both basic and translational research has laid the foundation for potential therapeutic applications. Beyond KP's function in the hypothalamus, it is also expressed in the placenta, liver, pancreas, adipose tissue, bone, and limbic regions, giving rise to several avenues of research for use in the diagnosis and treatment of pregnancy, metabolic, liver, bone, and behavioral disorders. The role played by NKB in stimulating the hypothalamic thermoregulatory center to mediate menopausal hot flashes has led to the development of medications that antagonize its action as a novel nonsteroidal therapeutic agent for this indication. Furthermore, the ability of NKB antagonism to partially suppress (but not abolish) the reproductive endocrine axis has supported its potential use for the treatment of various reproductive disorders including polycystic ovary syndrome, uterine fibroids, and endometriosis. This review will provide a comprehensive up-to-date overview of the preclinical and clinical data that have paved the way for the development of diagnostic and therapeutic applications of KP and NKB.

KNDy Neurons of the Hypothalamus and Their Role in GnRH Pulse Generation: an Update

There is considerable evidence that synchronized activity within a reciprocally connected population of cells in the arcuate nucleus (ARC) coexpressing kisspeptin, neurokinin B (NKB), and dynorphin (KNDy cells) is crucial for the generation of gonadotrophin-releasing hormone (GnRH) pulses in mammals. The initial "KNDy hypothesis" proposed that pulsatile GnRH secretion is elicited by episodic kisspeptin release from KNDy cells following synchronized activation and termination of the population by NKB and dynorphin, respectively. Since then, the role of KNDy cells as a critical component of the pulse generator has been further supported by studies at the single-cell level, demonstrating that the population is both necessary and sufficient for pulsatility. In addition, there have been considerable modifications and expansion of the original hypothesis, including work demonstrating the critical role of glutamate in synchronization of the KNDy cell network, functional interactions with other ARC subpopulations, and the existence of species differences in the role of dynorphin in pulse generation. Here we review these recent changes and discuss how the translation of these findings has led to the development of new therapies for disorders related to pulse generation. We also outline critical gaps in knowledge that are currently limiting the application of KNDy research in the clinic, particularly regarding the role of dynorphin in pulse generation in primates.

Key features of puberty onset and progression can help distinguish self-limited delayed puberty from congenital hypogonadotrophic hypogonadism

Introduction

Delayed puberty (DP) is a frequent concern for adolescents. The most common underlying aetiology is self-limited DP (SLDP). However, this can be difficult to differentiate from the more severe condition congenital hypogonadotrophic hypogonadism (HH), especially on first presentation of an adolescent patient with DP. This study sought to elucidate phenotypic differences between the two diagnoses, in order to optimise patient management and pubertal development.

Methods

This was a study of a UK DP cohort managed 2015-2023, identified through the NIHR clinical research network. Patients were followed longitudinally until adulthood, with a definite diagnosis made: SLDP if they had spontaneously completed puberty by age 18 years; HH if they had not commenced (complete, cHH), or had commenced but not completed puberty (partial, pHH), by this stage. Phenotypic data pertaining to auxology, Tanner staging, biochemistry, bone age and hormonal treatment at presentation and during puberty were retrospectively analysed.

Results

78 patients were included. 52 (66.7%) patients had SLDP and 26 (33.3%) patients had HH, comprising 17 (65.4%) pHH and 9 (34.6%) cHH patients. Probands were predominantly male (90.4%). Male SLDP patients presented with significantly lower height and weight standard deviation scores than HH patients (height p=0.004, weight p=0.021). 15.4% of SLDP compared to 38.5% of HH patients had classical associated features of HH (micropenis, cryptorchidism, anosmia, etc. p=0.023). 73.1% of patients with SLDP and 43.3% with HH had a family history of DP (p=0.007). Mean first recorded luteinizing hormone (LH) and inhibin B were lower in male patients with HH, particularly in cHH patients, but not discriminatory. There were no significant differences identified in blood concentrations of FSH, testosterone or AMH at presentation, or in bone age delay.

Discussion

Key clinical markers of auxology, associated signs including micropenis, and serum inhibin B may help distinguish between SLDP and HH in patients presenting with pubertal delay, and can be incorporated into clinical assessment to improve diagnostic accuracy for adolescents. However, the distinction between HH, particularly partial HH, and SLDP remains problematic. Further research into an integrated framework or scoring system would be useful in aiding clinician decision-making and optimization of treatment.  .

Unravelling a novel, promising and convenient tool for differential diagnosis of delayed puberty: GnRHa-stimulated inhibin B (GnRH-iB)

BACKGROUND

Etiological diagnosis of delayed puberty is difficult. Despite availability of various basal and stimulation tests differentiation between constitutional delay in puberty and hypogonadotropic hypogonadism is still challenging.

OBJECTIVE

To elucidate the role of GnRH agonist-stimulated inhibin B (GnRH-iB) for the differential diagnosis of delayed puberty.

STUDY DESIGN

Participants were recruited into "exploratory cohort" (n = 39) and "validation cohort" (n = 16). "Exploratory cohort" included children with spontaneous puberty and patients with hypogonadotropic hypogonadism. "Validation cohort" constituted children who presented with delayed puberty.

INTERVENTION AND OUTCOME

GnRHa (Triptorelin) stimulation test along with measurement of inhibin B level at 24 h after GnRHa injection was performed in all the study participants. Cut-offs for GnRH-iB were derived from the "exploratory cohort". These cut-offs were applied to the "validation cohort". Basal LH, basal inhibin B(INH-B), GnRHa-stimulated LH at 4 h (GnRH-LH) and GnRH-iB were evaluated for the prediction of onset of puberty on prospective follow-up.

RESULTS

GnRH-iB at a cut-off value of 113.5 pg/ml in boys and 72.6 pg/ml in girls had 100% sensitivity and specificity for the documentation of puberty. In the "validation cohort" basal LH, basal INH-B, GnRH-LH, and GnRH-iB had a diagnostic accuracy of 68.75%, 81.25%, 68.75% and 93.75% respectively, for the prediction of onset of puberty. Basal LH, basal INH-B and GnRH-LH used alone or in combination were inferior to GnRH-iB used alone.

CONCLUSION

GnRHa-stimulated inhibin B (GnRH-iB) is a convenient and easily employable test for the differentiation of constitutional delay in puberty from hypogonadotropic hypogonadism.

CTRI REGISTRATION NO

CTRI/2019/10/021570.

Considerations when treating male pubertal delay pharmacologically

INTRODUCTION

Delayed puberty, defined as the appearance of pubertal signs after the age of 14 years in males, usually affects psychosocial well-being. Patients and their parents show concern about genital development and stature. The condition is transient in most of the patients; nonetheless, the opportunity should not be missed to diagnose an underlying illness.

AREAS COVERED

The aetiologies of pubertal delay in males and their specific pharmacological therapies are discussed in this review.

EXPERT OPINION

High-quality evidence addressing the best pharmacological therapy approach for each aetiology of delayed puberty in males is scarce, and most of the current practice is based on small case series or unpublished experience. Male teenagers seeking attention for pubertal delay most probably benefit from medical treatment to avoid psychosocial distress. While watchful waiting is appropriate in 12- to 14-year-old boys when constitutional delay of growth and puberty (CGDP) is suspected, hormone replacement should not be delayed beyond the age of 14 years in order to avoid impairing height potential and peak bone mass. When primary or central hypogonadism is diagnosed, hormone replacement should be proposed by the age of 12 years provided that a functional central hypogonadism has been ruled out. Testosterone replacement regimens have been used for decades and are fairly standardised. Aromatase inhibitors have arisen as an interesting alternative for boy with CDGP and short stature. Gonadotrophin therapy seems more physiological in patients with central hypogonadism, but its relative efficacy and most adequate timing still need to be established.

Advances in clinical applications of kisspeptin-GnRH pathway in female reproduction

BACKGROUND

Kisspeptin is the leading upstream regulator of pulsatile and surge Gonadotrophin-Releasing Hormone secretion (GnRH) in the hypothalamus, which acts as the key governor of the hypothalamic-pituitary-ovary axis.

MAIN TEXT

Exogenous kisspeptin or its receptor agonist can stimulate GnRH release and subsequent physiological gonadotropin secretion in humans. Based on the role of kisspeptin in the hypothalamus, a broad application of kisspeptin and its receptor agonist has been recently uncovered in humans, including central control of ovulation, oocyte maturation (particularly in women at a high risk of ovarian hyperstimulation syndrome), test for GnRH neuronal function, and gatekeepers of puberty onset. In addition, the kisspeptin analogs, such as TAK-448, showed promising agonistic activity in healthy women as well as in women with hypothalamic amenorrhoea or polycystic ovary syndrome.

CONCLUSION

More clinical trials should focus on the therapeutic effect of kisspeptin, its receptor agonist and antagonist in women with reproductive disorders, such as hypothalamic amenorrhoea, polycystic ovary syndrome, and endometriosis.

An Approach to the Patient With Delayed Puberty

Pediatric endocrinologists often evaluate and treat youth with delayed puberty. Stereotypically, these patients are 14-year-old young men who present due to lack of pubertal development. Concerns about stature are often present, arising from gradual shifts to lower height percentiles on the population-based, cross-sectional curves. Fathers and/or mothers may have also experienced later than average pubertal onset. In this review, we will discuss a practical clinical approach to the evaluation and management of youth with delayed puberty, including the differential diagnosis and key aspects of evaluation and management informed by recent review of the existing literature. We will also discuss scenarios that pose additional clinical challenges, including: (1) the young woman whose case poses questions regarding how presentation and approach differs for females vs males; (2) the 14-year-old female or 16-year-old young man who highlight the need to reconsider the most likely diagnoses, including whether idiopathic delayed puberty can still be considered constitutional delay of growth and puberty at such late ages; and finally (3) the 12- to 13-year-old whose presentation raises questions about whether age cutoffs for the diagnosis and treatment of delayed puberty should be adjusted downward to coincide with the earlier onset of puberty in the general population.

Review of human genetic and clinical studies directly relevant to GnRH signalling

GnRH is the pivotal hormone in controlling the hypothalamic-pituitary gonadal (HPG) axis in humans and other mammalian species. GnRH function is influenced by a multitude of known and still unknown environmental and genetic factors. Molecular genetic studies on human families with hypogonadotropic hypogonadism over the past two decades have been instrumental in delineating the kisspeptin and neurokinin B signalling, which integrally modulates GnRH release from the hypothalamus. The identification of kisspeptin and neurokinin B ligand-receptor gene pair mutations in patients with absent puberty have paved the way to a greater understanding of the central regulation of the HPG cascade. In this article, we aim to review the literature on the genetic and clinical aspects of GnRH and its receptor, as well as the two ligand-receptor sets directly pertinent to the function of GnRH hormone signalling, kisspeptin/ kisspeptin receptor and NKB/NK3R.

The Reproductive Functions of the Human Brain Regions: A Systematic Review

Reproduction remains a vital characteristic of living things necessary for survival and continuity. Specific brain regions and structures are responsible for regulating the different aspects of human reproduction. This study systematically reviewed the brain regions that play structural, hormonal and physiological roles in controlling the various aspects of human reproduction from puberty, sexual function, gametogenesis, childbirth and fertility to infertility to inform advancement in research and therapeutic interventions in human reproductive disorders. A systematic literature search of online databases (MEDLINE, Europe PMC and Google Scholar) was made using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for observational and cross-sectional studies providing evidence for the role(s) of the brain region in human reproduction from the year 2011-2021. Out of 141 articles found, 15 studies met the inclusion criteria, including six cross-sectional and nine randomised controlled trials. The study acknowledged the roles of the pituitary gland, hypothalamus and pineal gland, widely known for regulating the human reproductive system in a gender-based approach while highlighting essential gaps and opportunities for future research. This review provides a 10-year update and overview of the role of different brain regions in human reproduction and will stimulate future research in human reproduction.

Accuracy of various tests alone and in combination to differentiate IHH from CDGP

CONTEXT

Constitutional delay in growth and puberty (CDGP) is a normal physiological variant of delayed puberty in both sexes and is the most common cause of delayed puberty. Idiopathic hypogonadotropic hypogonadism (IHH) is due to deficiency in or insensitivity to gonadotropin-releasing hormone (GnRH) with normal structure and function of the anterior pituitary after exclusion of secondary causes of hypogonadotropic hypogonadism. To differentiate CDGP from IHH is crucial because it not only helps in decision making in management but also lessen anxiety of the parents.

AIM

In this study we aimed to find out the accuracy of hormonal tests used individually as well as in various combinations to distinguish cases of IHH from CDGP.

METHODS

A cohort of 34 boys with delayed puberty were recruited in this study. Detailed history, clinical examination, hormonal analysis including basal serum testosterone, inhibin-B, LH, FSH as well as GnRH analogue stimulated gonadotrophins and testosterone along with hCG stimulated testosterone was done. At 6 monthly follow-up, detailed clinical examination was repeated and the cohort was followed until 2 years.

RESULTS

Out of the 29 boys taken for final analysis, CDGP was diagnosed in 23 boys and IHH in 6 boys. Basal LH, basal inhibin-B, 3 hours post leuprolide LH and 72 hours post hCG testosterone were significantly higher in CDGP than IHH. However, no statistically significant difference was observed between basal FSH, basal testosterone and 3 hours post leuprolide FSH between these two groups. When basal LH (cut-off <0.565 IU/L) and basal inhibin-B (cut-off <105 pg/ml) were taken together the sensitivity and specificity were increased to 100% as was for the combination of basal LH (cutoff <0.565 IU/L) and 3 hours post leuprolide LH (cutoff <6.16 IU/L) for diagnosis of IHH. Both combinations have PPV of 100% and NPV of 100%. A combination of 3 hours post leuprolide LH with 72 hours post hCG testosterone also has good sensitivity (100%), specificity (96%), PPV (90%) and NPV (100%).

CONCLUSION

Differentiating IHH from CDGP is a challenging task due to considerable overlap in their clinical as well as hormonal profiles. Therefore we suggest that a combination of basal LH and basal inhibin-B may be considered as a useful screening tool to differentiate IHH from CDGP rather than the cumbersome and invasive stimulation tests.

Genetics of pubertal timing

Puberty marks the end of childhood and is a period when individuals undergo physiological and psychological changes to achieve sexual maturation and fertility. The onset of puberty is first detected as an increase in pulsatile secretion of gonadotropin-releasing hormone (GnRH). Pubertal onset is regulated by genetic, nutritional, environmental, and socio-economic factors. Disturbances affecting pubertal timing result in adverse health conditions later in life. Human genetic studies show that around 50-80% of the variation in pubertal onset is genetically determined. The genetic control of pubertal timing has been a field of active investigation in attempt to better understand the neuroendocrine control of this relevant period of life. Large populational studies and patient cohort-based studies have provided insights into the genetic regulation of pubertal onset. In this review, we discuss these discoveries and discuss potential mechanisms for how implicated genes may affect pubertal timing.

Current concepts surrounding neonatal hormone therapy for boys with congenital hypogonadotropic hypogonadism

INTRODUCTION

Congenital hypogonadotropic hypogonadism (CHH) is a genetic disorder of reproduction and development, characterized by deficient gonadotropin-releasing hormone (GnRH) secretion or action, affecting 1-in-4,000-15,000 males. Micropenis and undescended testes are cardinal features of antenatal GnRH deficiency and could indicate absent minipuberty in the first postnatal months. In this review, we outline the pathophysiology and clinical consequences of absent minipuberty and its implications for optimal approaches to the endocrine management of affected boys.

AREAS COVERED

Deficient GnRH activity during fetal development and neonatal-infancy phase of minipuberty accounts for the diminished mass of Sertoli cells and seminiferous tubules among CHH males, enduring impairment of reproductive function even during gonadotropin replacement in adult life. In overcoming this obstacle, several clinical studies of neonatal gonadotropin replacement have consistently shown positive results in inducing testicular development and correcting cryptorchidism.

EXPERT OPINION

A high index of clinical suspicion, combined with hormonal testing undertaken in the postnatal period of 1-4 months, can reliably confirm or refute the diagnosis of CHH. Timely identification of CHH in affected male infants (having characteristic "red flag' developmental anomalies) opens up the possibility for gonadotropin replacement as a targeted therapy to restore the normal hormonal milieu of minipuberty. Further work is necessary in formulating optimal gonadotropin treatment regimens to be more widely adopted in clinical practice.

Insulin-like peptide 3 (INSL3) in congenital hypogonadotrophic hypogonadism (CHH) in boys with delayed puberty and adult men

BACKGROUND

Delayed puberty in males is almost invariably associated with constitutional delay of growth and puberty (CDGP) or congenital hypogonadotrophic hypogonadism (CHH). Establishing the cause at presentation is challenging, with "red flag" features of CHH commonly overlooked. Thus, several markers have been evaluated in both the basal state or after stimulation e.g. with gonadotrophin releasing hormone agonist (GnRHa).Insulin-like peptide 3 (INSL3) is a constitutive secretory product of Leydig cells and thus a possible candidate marker, but there have been limited data examining its role in distinguishing CDGP from CHH. In this manuscript, we assess INSL3 and inhibin B (INB) in two cohorts: 1. Adolescent boys with delayed puberty due to CDGP or CHH and 2. Adult men, both eugonadal and having CHH.

MATERIALS AND METHODS

Retrospective cohort studies of 60 boys with CDGP or CHH, as well as 44 adult men who were either eugonadal or had CHH, in whom INSL3, INB, testosterone and gonadotrophins were measured. Cohort 1: Boys with delayed puberty aged 13-17 years (51 with CDGP and 9 with CHH) who had GnRHa stimulation (subcutaneous triptorelin 100mcg), previously reported with respect to INB. Cohort 2: Adult cohort of 44 men (22 eugonadal men and 22 men with CHH), previously reported with respect to gonadotrophin responses to kisspeptin-54.

RESULTS

Median INSL3 was higher in boys with CDGP than CHH (0.35 vs 0.15 ng/ml; p=0.0002). Similarly, in adult men, median INSL3 was higher in eugonadal men than CHH (1.08 vs 0.05 ng/ml; p<0.0001). However, INSL3 more accurately differentiated CHH in adult men than in boys with delayed puberty (auROC with 95% CI in adult men: 100%, 100-100%; boys with delayed puberty: 86.7%, 77.7-95.7%).Median INB was higher in boys with CDGP than CHH (182 vs 59 pg/ml; p<0.0001). Likewise, in adult men, median INB was higher in eugonadal men than CHH (170 vs 36.5 pg/ml; p<0.0001). INB performed better than INSL3 in differentiating CHH in boys with delayed puberty (auROC 98.5%, 95.9-100%), than in adult men (auROC 93.9%, 87.2-100%).

CONCLUSION

INSL3 better identifies CHH in adult men, whereas INB better identifies CHH in boys with delayed puberty.

Interpretation of reproductive hormones before, during and after the pubertal transition-Identifying health and disordered puberty

Puberty is a process of transition from childhood to adult reproductive capacity, governed by the reactivation of the hypothalamic-pituitary-gonadal axis after a long period of dormancy in mid-childhood. As such, the reproductive hormones are in a state of flux during the adolescent years, and interpretation of both the onset of healthy, concordant puberty and the differentiation of precocious, delayed or disordered puberty, can be challenging. This review is focused on the description of the endocrine axes in healthy puberty and the markers of disorders of puberty that can aid diagnosis and management for patients with these conditions. It will cover the hypothalamic, pituitary and gonadal hormone systems, the dynamic changes that occur during puberty, conditions leading to precocious, delayed or absent puberty and other syndromes with disordered puberty, and the biochemical diagnosis of these different disorders of puberty.

Uterine kisspeptin receptor critically regulates epithelial estrogen receptor α transcriptional activity at the time of embryo implantation in a mouse model

Embryo implantation failure is a major cause of infertility in women of reproductive age and a better understanding of uterine factors that regulate implantation is required for developing effective treatments for female infertility. This study investigated the role of the uterine kisspeptin receptor (KISS1R) in the molecular regulation of implantation in a mouse model. To conduct this study, a conditional uterine knockout (KO) of Kiss1r was created using the Pgr-Cre (progesterone receptor-CRE recombinase) driver. Reproductive profiling revealed that while KO females exhibited normal ovarian function and mated successfully to stud males, they exhibited significantly fewer implantation sites, reduced litter size and increased neonatal mortality demonstrating that uterine KISS1R is required for embryo implantation and a healthy pregnancy. Strikingly, in the uterus of Kiss1r KO mice on day 4 (D4) of pregnancy, the day of embryo implantation, KO females exhibited aberrantly elevated epithelial ERα (estrogen receptor α) transcriptional activity. This led to the temporal misexpression of several epithelial genes [Cftr (Cystic fibrosis transmembrane conductance regulator), Aqp5 (aquaporin 5), Aqp8 (aquaporin 8) and Cldn7 (claudin 7)] that mediate luminal fluid secretion and luminal opening. As a result, on D4 of pregnancy, the lumen remained open disrupting the final acquisition of endometrial receptivity and likely accounting for the reduction in implantation events. Our data clearly show that uterine KISS1R negatively regulates ERα signaling at the time of implantation, in part by inhibiting ERα overexpression and preventing detrimentally high ERα activity. To date, there are no reports on the regulation of ERα by KISS1R; therefore, this study has uncovered an important and powerful regulator of uterine ERα during early pregnancy.

FSH-stimulated Inhibin B (FSH-iB): A Novel Marker for the Accurate Prediction of Pubertal Outcome in Delayed Puberty

BACKGROUND

Clinicians have long been struggling to find an effective tool to predict onset of puberty.

OBJECTIVE

To explore stimulability of inhibin B after exogenous FSH and its potential role for prediction of onset of puberty.

DESIGN AND PARTICIPANTS

Study subjects were enrolled into "exploratory cohort" (n = 42) and "validation cohort" (n = 19). The exploratory cohort was further divided into group 1 (healthy children with spontaneous puberty [SP], n = 26) and group 2 (patients with hypogonadotropic hypogonadism [HH], n = 16). The validation cohort included children who presented with complaints of delayed puberty.

INTERVENTION AND OUTCOME

Participants were subjected to FSH stimulation test and GnRH analogue stimulation test. Cutoffs derived from the exploratory cohort for basal and FSH stimulated inhibin B (FSH-iB) were applied on the validation cohort. Basal LH, GnRH analogue-stimulated LH, basal inhibin B, and FSH-iB were compared with clinical outcomes on a prospective follow-up for prediction of onset of puberty.

RESULTS

There was statistically significant increment in inhibin B after exogenous FSH in group 1 (SP) in both male (188.8 pg/mL; P = 0.002) and female (1065 pg/mL; P = 0.023) subjects. The increment was not statistically significant in group 2 (HH) in both sexes. FSH-iB at a cutoff of 116.14 pg/mL in males and 116.50 pg/mL in females had 100% sensitivity and specificity for labelling entry into puberty. On application of these cutoffs on the validation cohort, FSH-iB had 100% positive predictive value, negative predictive value, and diagnostic accuracy for prediction of pubertal onset.

CONCLUSION

Inhibin B was stimulable in both male and female subjects. FSH-iB can be considered a novel and promising investigation for prediction of onset of puberty. Future studies are required for further validation.

Clinical Potential of Kisspeptin in Reproductive Health

Kisspeptins are a family of hypothalamic neuropeptides that are essential for the regulation of reproductive physiology. Their importance in reproductive health became apparent in 2003, when loss-of-function variants in the gene encoding the kisspeptin receptor were reported to result in isolated congenital hypogonadotropic hypogonadism (CHH). It has since been ascertained that hypothalamic kisspeptin neurons regulate gonadotropin-releasing hormone (GnRH) secretion to thus stimulate the remainder of the reproductive endocrine axis. In this review, we discuss genetic variants that affect kisspeptin receptor signaling, summarize data on KISS1R agonists, and posit possible clinical uses of native and synthetic kisspeptin receptor agonists for the investigation and treatment of reproductive disorders.

Recent advances in understanding and managing Kallmann syndrome

Many of the recent advances in our understanding of human reproductive biology and its genetic basis have arisen directly via the genetic investigation of patients with Kallmann syndrome and their families. The disease is characterised by the association of an isolated defect in the secretion (or, less commonly, action) of gonadotropin-releasing hormone (GnRH) and consequent infertility, with anosmia and potentially other associated non-reproductive features. GnRH-producing neurons are located in the hypothalamic brain region after a peculiar migration during embryonic life. To date, different genes affecting GnRH neuron development/migration have so far been implicated in Kallmann syndrome, but our knowledge of the genetic basis of the syndrome remains incomplete. From a clinical point of view, the disease has suffered from a lack of definitive diagnosis and treatment, and although progress has been made in terms of timely diagnosis and evidence-based treatment of patients, implementation remains inconsistent. These aspects will be discussed in this review, which examines new strategies for arriving at more evidence-based and patient-centred medical practice in Kallmann syndrome.

Longitudinal Increases in Serum Insulin-like Factor 3 and Testosterone Determined by LC-MS/MS in Pubertal Danish Boys

BACKGROUND

Serum concentrations of the peptide hormone insulin-like factor 3 (INSL3) is a candidate marker for improved distinction between constitutional delay of growth and puberty (CDGP) and permanent hypogonadotropic hypogonadism (HH) in boys.

AIM

To assess the possible diagnostic role of LC-MS/MS-based INSL3 measurements as a marker of imminent puberty by comparison with testosterone (T) and luteinizing hormone (LH) levels in serum longitudinally collected from 18 healthy boys throughout puberty.

RESULTS

The first increase in serum LH was detected on average 4 months earlier, as compared with the first observed increases in INSL3 and T. When comparing the 2 testicular hormones only, we found that in 22% (4 of 18) of the boys the first increase in serum INSL3 was observed prior to the first observed increase in T, whereas in 44% (8 of 18) the first increase in T was observed before the first observed increase in INSL3. In the remaining 6 boys, the 2 testicular hormones showed the first increase at the same examination.

CONCLUSION

In some boys with delayed puberty, the first indication of testicular maturation may be detectable by observing serum INSL3. Further studies of LC-MS/MS determination of serum INSL3 in patients with CDGP and HH are warranted.

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.