Anti-Müllerian Hormone, Growth Hormone, and Insulin-Like Growth Factor 1 Modulate the Migratory and Secretory Patterns of GnRH Neurons

Effects of growth hormone therapy on the onset and progression of pubertal development in girls with idiopathic short stature

OBJECTIVE

The aim of this study was to explore the impact of growth hormone (GH) therapy on the onset and progression of puberty in girls with idiopathic short stature.

METHODS

This study included 541 girls aged between 4.5 and 10.6 years who were receiving GH treatment, monitored over a 22-year follow-up period. Of these, 126 girls have been followed up to the onset of menarche. The participants were divided into two groups: a ISS control group (n = 66) and a group receiving daily GH treatment at a dose of 0.15 iu/kg (n = 60). We assessed the pubertal development and GH usage of these girls every three months.

RESULTS

(1) There was no significant difference in the onset of puberty between the growth hormone (GH) treatment group and the control group; however, the average duration of puberty was longer in the treatment group compared to the control group. (2) During puberty, there were no significant differences in height growth between the treated and untreated groups. (3) The duration of GH treatment showed a significant negative correlation with the age at onset of gonadal development and the age at menarche in females within the treatment group.

CONCLUSION

GH treatment does not seem to accelerate the onset of puberty but may extend its duration, without significantly impacting height growth during puberty. Additionally, longer GH treatment duration is linked to earlier gonadal development and menarche in females.

SEMA6A drives GnRH neuron-dependent puberty onset by tuning median eminence vascular permeability

Innervation of the hypothalamic median eminence by Gonadotropin-Releasing Hormone (GnRH) neurons is vital to ensure puberty onset and successful reproduction. However, the molecular and cellular mechanisms underlying median eminence development and pubertal timing are incompletely understood. Here we show that Semaphorin-6A is strongly expressed by median eminence-resident oligodendrocytes positioned adjacent to GnRH neuron projections and fenestrated capillaries, and that Semaphorin-6A is required for GnRH neuron innervation and puberty onset. In vitro and in vivo experiments reveal an unexpected function for Semaphorin-6A, via its receptor Plexin-A2, in the control of median eminence vascular permeability to maintain neuroendocrine homeostasis. To support the significance of these findings in humans, we identify patients with delayed puberty carrying a novel pathogenic variant of SEMA6A. In all, our data reveal a role for Semaphorin-6A in regulating GnRH neuron patterning by tuning the median eminence vascular barrier and thereby controlling puberty onset.

Insulin-like Growth Factor 1, Growth Hormone, and Anti-Müllerian Hormone Receptors Are Differentially Expressed during GnRH Neuron Development

Gonadotropin-releasing hormone (GnRH) neurons are key neuroendocrine cells in the brain as they control reproduction by regulating hypothalamic-pituitary-gonadal axis function. In this context, anti-Müllerian hormone (AMH), growth hormone (GH), and insulin-like growth factor 1 (IGF1) were shown to improve GnRH neuron migration and function in vitro. Whether AMH, GH, and IGF1 signaling pathways participate in the development and function of GnRH neurons in vivo is, however, currently still unknown. To assess the role of AMH, GH, and IGF1 systems in the development of GnRH neuron, we evaluated the expression of AMH receptors (AMHR2), GH (GHR), and IGF1 (IGF1R) on sections of ex vivo mice at different development stages. The expression of AMHR2, GHR, and IGF1R was assessed by immunofluorescence using established protocols and commercial antibodies. The head sections of mice were analyzed at E12.5, E14.5, and E18.5. In particular, at E12.5, we focused on the neurogenic epithelium of the vomeronasal organ (VNO), where GnRH neurons, migratory mass cells, and the pioneering vomeronasal axon give rise. At E14.5, we focused on the VNO and nasal forebrain junction (NFJ), the two regions where GnRH neurons originate and migrate to the hypothalamus, respectively. At E18.5, the median eminence, which is the hypothalamic area where GnRH is released, was analyzed. At E12.5, double staining for the neuronal marker ß-tubulin III and AMHR2, GHR, or IGF1R revealed a signal in the neurogenic niches of the olfactory and VNO during early embryo development. Furthermore, IGF1R and GHR were expressed by VNO-emerging GnRH neurons. At E14.5, a similar expression pattern was found for the neuronal marker ß-tubulin III, while the expression of IGF1R and GHR began to decline, as also observed at E18.5. Of note, hypothalamic GnRH neurons labeled for PLXND1 tested positive for AMHR2 expression. Ex vivo experiments on mouse sections revealed differential protein expression patterns for AMHR2, GHR, and IGF1R at any time point in development between neurogenic areas and hypothalamic compartments. These findings suggest a differential functional role of related systems in the development of GnRH neurons.

Autism-linked NLGN3 is a key regulator of gonadotropin-releasing hormone deficiency

Gonadotropin-releasing hormone (GnRH) deficiency (GD) is a disorder characterized by absent or delayed puberty, with largely unknown genetic causes. The purpose of this study was to obtain and exploit gene expression profiles of GnRH neurons during development to unveil novel biological mechanisms and genetic determinants underlying GD. Here, we combined bioinformatic analyses of immortalized and primary embryonic GnRH neuron transcriptomes with exome sequencing from GD patients to identify candidate genes implicated in the pathogenesis of GD. Among differentially expressed and filtered transcripts, we found loss-of-function (LoF) variants of the autism-linked neuroligin 3 (NLGN3) gene in two unrelated patients co-presenting with GD and neurodevelopmental traits. We demonstrated that NLGN3 is upregulated in maturing GnRH neurons and that NLGN3 wild-type, but not mutant, protein promotes neuritogenesis when overexpressed in developing GnRH cells. Our data represent proof of principle that this complementary approach can identify new candidate GD genes and demonstrate that LoF NLGN3 variants can contribute to GD. This novel genotype-phenotype correlation implies common genetic mechanisms underlying neurodevelopmental disorders, such as GD and autistic spectrum disorder.

Effects of Growth Hormone on Adult Human Gonads: Action on Reproduction and Sexual Function

Growth hormone (GH), which is commonly considered to be a promoter of growth and development, has direct and indirect effects on adult gonads that influence reproduction and sexual function of humans and nonhumans. GH receptors are expressed in adult gonads in some species including humans. For males, GH can improve the sensitivity of gonadotropins, contribute to testicular steroidogenesis, influence spermatogenesis possibly, and regulate erectile function. For females, GH can modulate ovarian steroidogenesis and ovarian angiogenesis, promote the development of ovarian cells, enhance the metabolism and proliferation of endometrial cells, and ameliorate female sexual function. Insulin-like growth factor-1 (IGF-1) is the main mediator of GH. In vivo, a number of the physiological effects of GH are mediated by GH-induced hepatic IGF-1 and local IGF-1. In this review, we highlight the roles of GH and IGF-1 in adult human gonads, clarify potential mechanisms, and explore the efficacy and the risk of GH supplementation in associated deficiency and assisted reproductive technologies. Besides, the effects of excess GH on adult human gonads are discussed as well.

Male Idiopathic Hypogonadotropic Hypogonadism: Serum Insulin-like Growth Factor-1 and Oestradiol Levels

Background

Idiopathic hypogonadotropic hypogonadism (IHH) is a form of male infertility caused by a congenital defect in the secretion or action of gonadotropin-releasing hormone from the hypothalamus. Oestradiol emerged as the main sex steroid in the regulation of the hypothalamic-pituitary-testicular axis, reproductive function and growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis in men. Moreover, GH/IGF-1 axis has been suggested to play a role in IHH.

Aims

This study evaluated serum IGF-1 in IHH men and controls. Furthermore, we evaluated the association between serum total oestradiol (TE2) and IGF-1 levels in patients and controls. Parameters including age, body mass index and fertility history were analysed.

Settings and Design

This prospective study was conducted at the Royan institute.

Materials and Methods

In 20 men with IHH and 20 controls, serum IGF-1 levels were estimated using chemiluminescence immunoassay and serum E2 levels were assessed by means of the electrochemiluminescence method.

Statistical Analysis Used

Kolmogorov-Smirnov test, parametric t-test or the Mann-Whitney and the Pearson correlation coefficient were performed. SPSS version 22 was used for the analysis of data.

Results

There was a significant decrease in serum IGF-1 levels in IHH patients compared with controls (145.1 ± 8.9 ng/ml vs. 229.6 ± 7.3 ng/ml P < 0.001, respectively). Furthermore, a significant decrease was observed in TE2 levels in IHH male patients (12.3 ± 2.5 pg/ml) compared with controls (31.9 ± 5.3 pg/ml P < 0.001). A positive correlation was observed between serum IGF-1 and TE2 levels in the total number of participants, suggesting that E2 deficiency in IHH cases can explain the lower levels of serum IGF-1.

Conclusions

These findings suggest that the reduction in IGF-1 levels may be associated with the influence of E2 on the GH/IGF-1 axis, and may confirm the role of the GH/IGF-1 axis in IHH. Further investigations will be required to determine the exact mechanisms by which E2 and IGF-1 affect the reproductive neuroendocrine function.

Timing of Puberty, Pubertal Growth, and Adult Height in Short Children Born Small for Gestational Age Treated With Growth Hormone

CONTEXT

Growth hormone (GH) is used to treat short children born small for gestational age (SGA); however, the effects of treatment on pubertal timing and adult height are rarely studied.

OBJECTIVE

To evaluate adult height and peak height velocity in short GH-treated SGA children.

METHODS

Prospective longitudinal multicenter study. Participants were short children born SGA treated with GH therapy (n = 102). Adult height was reported in 47 children. A reference cohort of Danish children was used. Main outcome measures were adult height, peak height velocity, age at peak height, and pubertal onset. Pubertal onset was converted to SD score (SDS) using Danish reference data.

RESULTS

Gain in height SDS from start of treatment until adult height was significant in both girls (0.94 [0.75; 1.53] SDS, P = .02) and boys (1.57 [1.13; 2.15] SDS, P < .001). No difference in adult height between GH dosage groups was observed. Peak height velocity was lower than a reference cohort for girls (6.5 [5.9; 7.6] cm/year vs 7.9 [7.4; 8.5] cm/year, P < .001) and boys (9.5 [8.4; 10.7] cm/year vs 10.1 [9.7; 10.7] cm/year, P = .002), but no difference in age at peak height velocity was seen. Puberty onset was earlier in SGA boys than a reference cohort (1.06 [-0.03; 1.96] SDS vs 0 SDS, P = .002) but not in girls (0.38 [-0.19; 1.05] SDS vs 0 SDS, P = .18).

CONCLUSION

GH treatment improved adult height. Peak height velocity was reduced, but age at peak height velocity did not differ compared with the reference cohort. SGA boys had an earlier pubertal onset compared with the reference cohort.

Quantitative proteomics analysis to assess protein expression levels in the ovaries of pubescent goats

Background

Changes in the abundance of ovarian proteins play a key role in the regulation of reproduction. However, to date, no studies have investigated such changes in pubescent goats. Herein we applied isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography–tandem mass spectrometry to analyze the expression levels of ovarian proteins in pre-pubertal (n = 3) and pubertal (n = 3) goats.

Results

Overall, 7,550 proteins were recognized; 301 (176 up- and 125 downregulated) were identified as differentially abundant proteins (DAPs). Five DAPs were randomly selected for expression level validation by Western blotting; the results of Western blotting and iTRAQ analysis were consistent. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that DAPs were enriched in olfactory transduction, glutathione metabolism, and calcium signaling pathways. Besides, gene ontology functional enrichment analysis revealed that several DAPs enriched in biological processes were associated with cellular process, biological regulation, metabolic process, and response to stimulus. Protein–protein interaction network showed that proteins interacting with CDK1, HSPA1A, and UCK2 were the most abundant.

Conclusions

We identified 301 DAPs, which were enriched in olfactory transduction, glutathione metabolism, and calcium signaling pathways, suggesting the involvement of these processes in the onset of puberty. Further studies are warranted to more comprehensively explore the function of the identified DAPs and aforementioned signaling pathways to gain novel, deeper insights into the mechanisms underlying the onset of puberty.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08699-y.

A Novel Loss-of-Function SEMA3E Mutation in a Patient with Severe Intellectual Disability and Cognitive Regression

Intellectual disability (ID) is a neurological disorder arising from early neurodevelopmental defects. The underlying genetic and molecular mechanisms are complex, but are thought to involve, among others, alterations in genes implicated in axon guidance and/or neural circuit formation as demonstrated by studies on mouse models. Here, by combining exome sequencing with in silico analyses, we identified a patient affected by severe ID and cognitive regression, carrying a novel loss-of-function variant in the semaphorin 3E (SEMA3E) gene, which encodes for a key secreted cue that controls mouse brain development. By performing ad hoc in vitro and ex vivo experiments, we found that the identified variant impairs protein secretion and hampers the binding to both embryonic mouse neuronal cells and tissues. Further, we revealed SEMA3E expression during human brain development. Overall, our findings demonstrate the pathogenic impact of the identified SEMA3E variant and provide evidence that clinical neurological features of the patient might be due to a defective SEMA3E signaling in the brain.

The Differential Roles for Neurodevelopmental and Neuroendocrine Genes in Shaping GnRH Neuron Physiology and Deficiency

Gonadotropin releasing hormone (GnRH) neurons are hypothalamic neuroendocrine cells that control sexual reproduction. During embryonic development, GnRH neurons migrate from the nose to the hypothalamus, where they receive inputs from several afferent neurons, following the axonal scaffold patterned by nasal nerves. Each step of GnRH neuron development depends on the orchestrated action of several molecules exerting specific biological functions. Mutations in genes encoding for these essential molecules may cause Congenital Hypogonadotropic Hypogonadism (CHH), a rare disorder characterized by GnRH deficiency, delayed puberty and infertility. Depending on their action in the GnRH neuronal system, CHH causative genes can be divided into neurodevelopmental and neuroendocrine genes. The CHH genetic complexity, combined with multiple inheritance patterns, results in an extreme phenotypic variability of CHH patients. In this review, we aim at providing a comprehensive and updated description of the genes thus far associated with CHH, by dissecting their biological relevance in the GnRH system and their functional relevance underlying CHH pathogenesis.

Role of the GH-IGF1 axis on the hypothalamus-pituitary-testicular axis function: lessons from Laron syndrome

BACKGROUND

Animal studies suggest that insulin-like growth factor 1 (IGF1) may influence the function of the hypothalamus-pituitary-testicular axis, especially in childhood, but the evidence in humans is scanty. Laron syndrome, a human model of IGF1 deficiency, may help to solve this issue.

PURPOSE

This systematic review aims to analyze puberty onset and progression, testicular volume, gonadotropin, and total testosterone serum levels, sperm parameters and fertility, and penile length in patients with Laron syndrome.

METHODS

Specific keywords were used. All data on male patients with Laron syndrome were included.

RESULTS

Seventeen articles matched the inclusion criteria and were entered in the analysis, for a total of 125 male patients. Puberty was absent in 8.9% and delayed in 35.6% of untreated patients of pubertal age. After onset, the duration of the pubertal process was prolonged in 76.9% of untreated patients. The growth spurt was absent in 52.6% and delayed in 31.6% of untreated patients. The testicular volume was small in the two patients who did not receive any treatment. Treatment with IGF1 increased gonadotropin and testosterone serum levels in five out of five patients of pubertal age. No effect was found in four out of four patients younger than 5 years. No study reported data on sperm parameters and fertility. Micropenis occurred in 67.2% of patients.

CONCLUSION AND FUTURE PERSPECTIVES

Delayed puberty is common in patients with Laron syndrome. The growth hormone-IGF1 axis may influence the time of puberty onset. Serum levels of IGF1 should be investigated in children with delayed puberty, scarce progression of testicular growth, and/or micropenis. IGF1 levels might be measured in children with delayed puberty, poor testicular growth, and/or micropenis.