Neurobiology of puberty and its disorders

My 28 Days - a global digital women's health initiative for evaluation and management of secondary amenorrhea: case report and literature review

There is a need to close the gap between knowledge and action in health care. Effective care requires a convenient and reliable distribution process. As global internet and mobile communication increase capacity, innovative approaches to digital health education platforms and care delivery are feasible. We report the case of a young African woman who developed acute secondary amenorrhea at age 18. Subsequently, she experienced a 10-year delay in the diagnosis of the underlying cause. A global digital medical hub focused on women's health and secondary amenorrhea could reduce the chance of such mismanagement. Such a hub would establish more efficient information integration and exchange processes to better serve patients, family caregivers, health care providers, and investigators. Here, we show proof of concept for a global digital medical hub for women's health. First, we describe the physiological control systems that govern the normal menstrual cycle, and review the pathophysiology and management of secondary amenorrhea. The symptom may lead to broad and profound health implications for the patient and extended family members. In specific situations, there may be significant morbidity related to estradiol deficiency: (1) reduced bone mineral density, 2) cardiovascular disease, and 3) cognitive decline. Using primary ovarian insufficiency (POI) as the paradigm condition, the Mary Elizabeth Conover Foundation has been able to address the specific global educational needs of these women. The Foundation did this by creating a professionally managed Facebook group specifically for these women. POI most commonly presents with secondary amenorrhea. Here we demonstrate the feasibility of conducting a natural history study on secondary amenorrhea with international reach to be coordinated by a global digital medical hub. Such an approach takes full advantage of internet and mobile device communication systems. We refer to this global digital women's health initiative as My 28 Days®.

A mouse model mimicking gender-affirming treatment with pubertal suppression followed by testosterone in transmasculine youth

STUDY QUESTION

Can mice serve as a translational model to examine the reproductive consequences of pubertal suppression with GnRH agonist (GnRHa) followed by testosterone (T) administration, a typical therapy in peripubertal transmasculine youth?

SUMMARY ANSWER

An implanted depot with 3.6 mg of GnRHa followed by T enanthate at 0.45 mg weekly can be used in peripubertal female mice for investigating the impact of gender-affirming hormone therapy in transmasculine youth.

WHAT IS KNOWN ALREADY

There is limited knowledge available in transgender medicine to provide evidence-based fertility care, with the current guidelines being based on the assumption of fertility loss. We recently successfully developed a mouse model to investigate the reproductive consequences of T therapy given to transgender men. On the other hand, to our knowledge, there is no mouse model to assess the reproductive outcomes in peripubertal transmasculine youth.

STUDY DESIGN, SIZE, DURATION

A total of 80 C57BL/6N female mice were used in this study, with n = 7 mice in each experimental group.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We first assessed the effectiveness of GnRHa in arresting pubertal development in the female mice. In this experiment, 26-day-old female mice were subcutaneously implanted with a GnRHa (3.6 mg) depot. Controls underwent a sham surgery. Animals were euthanized at 3, 9, 21 and 28 days after the day of surgery. In the second experiment, we induced a transmasculine youth mouse model. C57BL/6N female mice were subcutaneously implanted with a 3.6 mg GnRHa depot on postnatal day 26 for 21 days and this was followed by weekly injections of 0.45 mg T enanthate for 6 weeks. The control for the GnRH treatment was sham surgery and the control for T treatment was sesame oil vehicle injections. Animals were sacrificed 0.5 weeks after the last injection. The data collected included the day of the vaginal opening and first estrus, daily vaginal cytology, weekly and terminal reproductive hormones levels, body/organ weights, ovarian follicular distribution and corpora lutea (CL) counts.

MAIN RESULTS AND THE ROLE OF CHANCE

GnRHa implanted animals remained in persistent diestrus and had reduced levels of FSH (P = 0.0013), LH (P = 0.0082) and estradiol (P = 0.0155), decreased uterine (P < 0.0001) and ovarian weights (P = 0.0002), and a lack of CL at 21 days after GnRHa implantation. T-only and GnRHa+T-treated animals were acyclic throughout the treatment period, had sustained elevated levels of T, suppressed LH levels (P < 0.0001), and an absence of CL compared to controls (P < 0.0001). Paired ovarian weights were reduced in the T-only and GnRHa+T groups compared with the control and GnRHa-only groups.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Although it is an appropriate tool to provide relevant findings, precaution is needed to extrapolate mouse model results to mirror human reproductive physiology.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this study describes the first mouse model mimicking gender-affirming hormone therapy in peripubertal transmasculine youth. This model provides a tool for researchers studying the effects of GnRHa-T therapy on other aspects of reproduction, other organ systems and transgenerational effects. The model is supported by GnRHa suppressing puberty and maintaining acyclicity during T treatment, lower LH levels and absence of CL. The results also suggest GnRHa+T therapy in peripubertal female mice does not affect ovarian reserve, since the number of primordial follicles was not affected by treatment.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Michigan Institute for Clinical and Health Research grants KL2 TR 002241 and UL1 TR 002240 (C.D.C.); National Institutes of Health grants F30-HD100163 and T32-HD079342 (H.M.K.); University of Michigan Office of Research funding U058227 (A.S.); American Society for Reproductive Medicine/Society for Reproductive Endocrinology and Infertility grant (M.B.M.); and National Institutes of Health R01-HD098233 (M.B.M.). The University of Virginia Center for Research in Reproduction Ligand Assay and Analysis Core Facility was supported by the Eunice Kennedy Shriver NICHD/NIH grants P50-HD028934 and R24-HD102061. The authors declare that they have no competing interests.

Hypothalamic-Pituitary-Gonadal Axis Disorders Impacting Fertility in Both Sexes and the Potential of Kisspeptin-Based Therapies to Treat Them

Impaired function of the hypothalamic-pituitary-gonadal (HPG) axis can lead to a vast array of reproductive disorders some of which are inherited or acquired, but many are of unknown etiology. Among the clinical consequences of HPG impairment, infertility is quite common. According to the latest report from the World Health Organization, the global prevalence of infertility during a person's lifetime is a staggering 17.5% which translate into 1 out of every 6 people experiencing it. In both sexes, infertility is associated with adverse health events, and if unresolved, infertility can cause substantial psychological stress, social stigmatization, and economic strain. Even though significant advances have been made in the management and treatment of infertility, low or variable efficacy of treatments and medication adverse effects still pose a significant problem. However, the discovery that in humans inactivating mutations in the gene encoding the kisspeptin receptor (Kiss1R) results in pubertal failure and infertility has expanded our understanding of the mechanisms underlying the neuroendocrine control of reproduction, opening up potential new therapies for the treatment of infertility disorders. In this chapter we provide an overview of common infertility disorders affecting men and women, their recommended treatments, and the potential of kisspeptin-based pharmacotherapies to treat them.

Trans Dermal Testosterone Compared to Intramuscular Testosterone for Young Males with Delayed Puberty: A PRISMA Guided Systematic Review

Background

Challenges in selecting the right formulation of testosterone (TE) for young males with delayed puberty (DP) arise from the fact that there is limited evidence based guidelines in recommending the most efficient and safe formulation of TE.

Objective

To evaluate the existing evidence and systematically review the interventional effects of transdermal TE to other modes of TE administration for the treatment of DP among young and adolescent males.

Methods

All types of methodologies published in English were searched from the data sources including MEDLINE, Embase, Cochrane Reviews, Web of Science, AMED and Scopus from 2015 till 2022. Boolean operators with keywords "types of TE", "modes of TE administration", "DP", "transdermal TE", "constitutional delay of growth and puberty, (CDGP)" "adolescent boys" and "hypogonadism" to optimize the search results. The main outcomes of concern were optimal serum TE level, body mass index, height velocity, testicular volume, pubertal stage (Tanner), The secondary outcomes included in this study were adverse events and patient satisfaction.

Results

After screening 126 articles, 39 full texts were reviewed. Only five studies could be included after careful screening and rigid quality assessments. Most studies were at high or unclear risk of bias with short duration and follow up periods. Only one study was a clinical trial covering all the outcomes of interests.

Conclusion

This study points out the favorable effects of transdermal TE treatment for DP in boys, while the existence of the vast gap in research needs to be acknowledged. Despite the utmost demand in an appropriate TE treatment for young males with DP, scarce efforts and trials are being undertaken to provide clear clinical guidance of treatment. Quality of life, cardiac events, metabolic parameters, coagulation profiles are important aspects of the treatment are overlooked and under evaluated in most studies.

Systematic Review Registration

PROSPERO CRD 42022369699.

Central Irisin Signaling Is Required for Normal Timing of Puberty in Female Mice

Timing of puberty requires exquisite coordination of genes, hormones, and brain circuitry. An increasing level of body adiposity, signaled to the brain via the fat-derived hormone leptin, is recognized as a major factor controlling puberty onset. However, it is clear that leptin is not the only metabolic cue regulating puberty, and that developmental regulation of this process also involves tissues other than adipose, with muscle development potentially playing a role in the timing of puberty. The proteolytic processing of fibronectin type 3 domain-containing protein 5 (FNDC5) releases a hormone, irisin. Irisin is primarily produced by muscle and is released into circulation, where levels increase dramatically as puberty approaches. We investigated the effects of a global deletion of the Fndc5 gene on pubertal timing. The absence of irisin induced a delay in puberty onset in female knockout mice compared with controls, without affecting body weight or gonadotropin-releasing hormone (GnRH) neuronal density. We next treated pre-pubertal wild-type male and female mice with an irisin receptor antagonist, cilengitide, for 7 days and observed a delay in first estrus occurrence compared to vehicle-treated control mice. Male puberty timing was unaffected. Next, we deleted the irisin receptor (integrin subunit alpha V) in all forebrain neurons and found a delay in the occurrence of first estrus in knockout females compared to controls. Taken together, these data suggest irisin plays a role in the timing of puberty onset in female mice via a centrally mediated mechanism.

Expression and functional analysis of GnRH at the onset of puberty in sheep

Gonadotropin-releasing hormone (GnRH) is a key factor at the onset of puberty. This decapeptide has been found in mammalian ovaries, but its regulatory mechanism in the ovary of sheep at the onset of puberty is not clear. This study investigated the coding sequence (CDS) of the GnRH gene in the ovary of Duolang sheep and the expression of GnRH mRNA in different tissues at the onset of puberty, and analyzed the effect of GnRH on ovarian granulosa cells (GCs) of Duolang sheep. The results showed that the GnRH CDS of sheep was cloned, the full length of the GnRH CDS in sheep ovary was 279 bp, and the nucleotide sequence was completely homologous to that in the hypothalamus. The expression of GnRH mRNA was highest in the hypothalamus and ovary. The expression of related hormones and receptors in GCs of Duolang sheep treated with different concentrations of GnRH for 24 h was affected. GnRH significantly inhibited LH synthesis and LHR expression in GCs. Low concentration (100 ng mL-1) had the most obvious therapeutic effect on follicle-stimulating hormone (FSH) and FSHR. Higher concentration (250 ng mL-1) significantly promoted estradiol and ERβ mRNA. These findings provide strong evidence that ovarian GnRH is an important regulatory factor at the onset of puberty in sheep.

PLXNB1 mutations in the etiology of idiopathic hypogonadotropic hypogonadism

Idiopathic hypogonadotropic hypogonadism (IHH) comprises a group of rare genetic disorders characterized by pubertal failure caused by gonadotropin-releasing hormone (GnRH) deficiency. Genetic factors involved in semaphorin/plexin signaling have been identified in patients with IHH. PlexinB1, a member of the plexin family receptors, serves as the receptor for semaphorin 4D (Sema4D). In mice, perturbations in Sema4D/PlexinB1 signaling leads to improper GnRH development, highlighting the importance of investigating PlexinB1 mutations in IHH families. In total, 336 IHH patients (normosmic IHH, n = 293 and Kallmann syndrome, n = 43) from 290 independent families were included in the present study. Six PLXNB1 rare sequence variants (p.N361S, p.V608A, p.R636C, p.V672A, p.R1031H, and p.C1318R) are described in eight normosmic IHH patients from seven independent families. These variants were examined using bioinformatic modeling and compared to mutants reported in PLXNA1. Based on these analyses, the variant p.R1031H was assayed for alterations in cell morphology, PlexinB1 expression, and migration using a GnRH cell line and Boyden chambers. Experiments showed reduced membrane expression and impaired migration in cells expressing this variant compared to the wild-type. Our results provide clinical, genetic, molecular/cellular, and modeling evidence to implicate variants in PLXNB1 in the etiology of IHH.

Polycystic Ovary Syndrome and the Neuroendocrine Consequences of Androgen Excess

Polycystic ovary syndrome (PCOS) is a major endocrine disorder strongly associated with androgen excess and frequently leading to female infertility. Although classically considered an ovarian disease, altered neuroendocrine control of gonadotropin-releasing hormone (GnRH) neurons in the brain and abnormal gonadotropin secretion may underpin PCOS presentation. Defective regulation of GnRH pulse generation in PCOS promotes high luteinizing hormone (LH) pulsatile secretion, which in turn overstimulates ovarian androgen production. Early and emerging evidence from preclinical models suggests that maternal androgen excess programs abnormalities in developing neuroendocrine circuits that are associated with PCOS pathology, and that these abnormalities are sustained by postpubertal elevation of endogenous androgen levels. This article will discuss experimental evidence, from the clinic and in preclinical animal models, that has significantly contributed to our understanding of how androgen excess influences the assembly and maintenance of neuroendocrine impairments in the female brain. Abnormal central gamma-aminobutyric acid (GABA) signaling has been identified in both patients and preclinical models as a possible link between androgen excess and elevated GnRH/LH secretion. Enhanced GABAergic innervation and drive to GnRH neurons is suspected to contribute to the pathogenesis and early manifestation of neuroendocrine derangement in PCOS. Accordingly, this article also provides an overview of GABA regulation of GnRH neuron function from prenatal development to adulthood to discuss possible avenues for future discovery research and therapeutic interventions. © 2022 American Physiological Society. Compr Physiol 12:3347-3369, 2022.

Aberrant Notch Signaling Pathway as a Potential Mechanism of Central Precocious Puberty

The Notch signaling pathway is highly conserved during evolution. It has been well documented that Notch signaling regulates cell proliferation, migration, and death in the nervous, cardiac, and endocrine systems. The Notch pathway is relatively simple, but its activity is regulated by numerous complex mechanisms. Ligands bind to Notch receptors, inducing their activation and cleavage. Various post-translational processes regulate Notch signaling by affecting the synthesis, secretion, activation, and degradation of Notch pathway-related proteins. Through such post-translational regulatory processes, Notch signaling has versatile effects in many tissues, including the hypothalamus. Recently, several studies have reported that mutations in genes related to the Notch signaling pathway were found in patients with central precocious puberty (CPP). CPP is characterized by the early activation of the hypothalamus–pituitary–gonadal (HPG) axis. Although genetic factors play an important role in CPP development, few associated genetic variants have been identified. Aberrant Notch signaling may be associated with abnormal pubertal development. In this review, we discuss the current knowledge about the role of the Notch signaling pathway in puberty and consider the potential mechanisms underlying CPP.

Genetic etiologies of central precocious puberty

Pubertal onset is a complex process, which is influenced by genetic and environmental factors, such as obesity and endocrine-disrupting chemicals. In addition, the timing of normal puberty varies between individuals and is a highly polygenic trait with both rare and common variants. Central precocious puberty (CPP) is defined as the early activation of the hypothalamic-pituitary-gonadal axis. Genetic factors are suggested to account for 50% to 80% of the variation in puberty initiation, as indicated by the greater concordance of pubertal timing observed in monozygotic twins than in dizygotic twins. Although genetic factors play a crucial role in CPP development, only few associated genes have been identified. To date, four monogenic genes have been identified: KISS1, KISS1R, MKRN3, and DLK1. Moreover, mutation prevalence in these genes varies considerably depending on the ethnicity of patients with CPP. This article reviews the current knowledge on the normal pubertal timing and physiology and discusses the CPP-causing genes.