Short-Term Exposure to Benzo(a)Pyrene Causes Disruption of GnRH Network in Zebrafish Embryos.

Benzo(a)pyrene (BaP), a polycyclic aromatic hydrocarbon, is considered a common endocrine disrupting chemical (EDC) with mutagenic and carcinogenic effects. In this work, we evaluated the effects of BaP on the hypothalamo-pituitary-gonadal axis (HPG) of zebrafish embryos. The embryos were treated with 5 and 50 nM BaP from 2.5 to 72 hours post-fertilization (hpf) and obtained data were compared with those from controls. We followed the entire development of gonadotropin releasing hormone (GnRH3) neurons that start to proliferate from the olfactory region at 36 hpf, migrate at 48 hpf and then reach the pre-optic area and the hypothalamus at 72 hpf. Interestingly, we observed a compromised neuronal architecture of the GnRH3 network after the administration of 5 and 50 nM BaP. Given the toxicity of this compound, we evaluated the expression of genes involved in antioxidant activity, oxidative DNA damage and apoptosis and we found an upregulation of these pathways. Consequently, we performed a TUNEL assay and we confirmed an increment of cell death in brain of embryos treated with BaP. In conclusion our data reveal that short-term exposure of zebrafish embryos to BaP affects GnRH3 development likely through a neurotoxic mechanism.

Defective jagged-1 signaling affects GnRH development and contributes to congenital hypogonadotropic hypogonadism.

In vertebrate species, fertility is controlled by gonadotropin-releasing hormone (GnRH) neurons. GnRH cells arise outside the central nervous system, in the developing olfactory pit, and migrate along olfactory/vomeronasal/terminal nerve axons into the forebrain during embryonic development. Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome are rare genetic disorders characterized by infertility, and they are associated with defects in GnRH neuron migration and/or altered GnRH secretion and signaling. Here, we documented the expression of the jagged-1/Notch signaling pathway in GnRH neurons and along the GnRH neuron migratory route both in zebrafish embryos and in human fetuses. Genetic knockdown of the zebrafish ortholog of JAG1 (jag1b) resulted in altered GnRH migration and olfactory axonal projections to the olfactory bulbs. Next-generation sequencing was performed in 467 CHH unrelated probands, leading to the identification of heterozygous rare variants in JAG1. Functional in vitro validation of JAG1 mutants revealed that 7 out of the 9 studied variants exhibited reduced protein levels and altered subcellular localization. Together our data provide compelling evidence that Jag1/Notch signaling plays a prominent role in the development of GnRH neurons, and we propose that JAG1 insufficiency may contribute to the pathogenesis of CHH in humans.

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.

Genetic and phenotypic differences between sexes in congenital hypogonadotropic hypogonadism (CHH): Large cohort analysis from a single tertiary centre.

Background: Congenital hypogonadotropic hypogonadism (CHH) is a condition with a strong genetic background, caused by a deficient production, secretion, or action of gonadotropin-releasing hormone (GnRH). Published data on CHH cohorts indicate a male predominance, although this is not supported by our current understandings. Aims: In order to unravel the possible causes or contributors to such epidemiological sex difference, the aim of our study is to investigate differences in genetic background and clinical presentation between males and females in a large cohort of CHH patients. Materials and methods: We enrolled 338 CHH patients with absent or arrested pubertal development, referred to our Center from 01/2016. Data collection included clinical assessment at diagnosis and genetic analysis performed by next generation sequencing (NGS), employing a custom panel of 28 candidate genes. Results: Among 338 patients 94 were female (F) and 244 male (M), with a ratio of 1:2.6. We found that 36.09% (122/338) of patients harbored potentially pathogenic rare genetic variants (RVs) with no significant differences between sexes; on the other hand, a significantly higher frequency of oligogenicity was observed in females (F 9,57% 9/94 vs M 3,69% 9/244, P = 0.034). The prevalence of non-reproductive phenotypic features was significantly higher (P = 0.01) in males (53/228, 23.2%) than in females (10/93, 10.8%): in particular, kidney abnormalities affected only male patients and midline defects had a significantly higher prevalence in males (P = 0.010). Finally, BMI SDS was -0.04 ± 1.09 in females and 0.69 ± 1.51 in males, with a statistically significant difference between groups (P = <0.001). Conclusion: Our data confirm the male predominance in CHH and identify some differences with regard to the clinical presentation between males and females that could indicate a variable expression of genetic rare variants and a dimorphic modulation of phenotype according to metabolic/behavioral factors, which will need to be substantiated and investigated by further studies.

The genetic diagnosis of rare endocrine disorders of sex development and maturation: a survey among Endo-ERN centres.

Differences of sex development and maturation (SDM) represent a heterogeneous puzzle of rare conditions with a large genetic component whose management and treatment could be improved by an accurate classification of underlying molecular conditions, and next-generation sequencing (NGS) should represent the most appropriate approach. Therefore, we conducted a survey dedicated to the use and potential outcomes of NGS for SDM disorders diagnosis among the 53 health care providers (HCP) of the European Reference Network for rare endocrine conditions. The response rate was 49% with a total of 26 HCPs from 13 countries. All HCPs, except 1, performed NGS investigations for SDM disorders on 6720 patients, 3764 (56%) with differences of sex development (DSD), including 811 unexplained primary ovarian insufficiency, and 2956 (44%) with congenital hypogonadotropic hypogonadism (CHH). The approaches varied from targeted analysis of custom gene panels (range: 11-490 genes) in 81.5% of cases or whole exome sequencing with the extraction of a virtual panel in the remaining cases. These analyses were performed for diagnostic purposes in 21 HCPs, supported by the National Health Systems in 16 cases. The likelihood of finding a variant ranged between 7 and 60%, mainly depending upon the number of analysed genes or criteria used for reporting, most HCPs also reporting variants of uncertain significance. These data illustrate the status of genetic diagnosis of DSD and CHH across Europe. In most countries, these analyses are performed for diagnostic purposes, yielding highly variable results, thus suggesting the need for harmonization and general improvements of NGS approaches.

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.

Genetic architecture of self-limited delayed puberty and congenital hypogonadotropic hypogonadism.

Distinguishing between self limited delayed puberty (SLDP) and congenital hypogonadotropic hypogonadism (CHH) may be tricky as they share clinical and biochemical characteristics. and appear to lie within the same clinical spectrum. However, one is classically transient (SDLP) while the second is typically a lifetime condition (CHH). The natural history and long-term outcomes of these two conditions differ significantly and thus command distinctive approaches and management. Because the first presentation of SDLP and CHH is very similar (delayed puberty with low LH and FSH and low sex hormones), the scientific community is scrambling to identify diagnostic tests that can allow a correct differential diagnosis among these two conditions, without having to rely on the presence or absence of phenotypic red flags for CHH that clinicians anyway seem to find hard to process. Despite the heterogeneity of genetic defects so far reported in DP, genetic analysis through next-generation sequencing technology (NGS) had the potential to contribute to the differential diagnostic process between SLDP and CHH. In this review we will provide an up-to-date overview of the genetic architecture of these two conditions and debate the benefits and the bias of performing genetic analysis seeking to effectively differentiate between these two conditions.

Long Non-Coding RNAs: Role in Testicular Cancers.

In the last few years lncRNAs have gained increasing attention among the scientific community, thanks to the discovery of their implication in many physio-pathological processes. In particular, their contribution to tumor initiation, progression, and response to treatment has attracted the interest of experts in the oncologic field for their potential clinical application. Testicular cancer is one of the tumors in which lncRNAs role is emerging. Said malignancies already have very effective treatments, which although lead to the development of quite serious treatment-related conditions, such as secondary tumors, infertility, and cardiovascular diseases. It is therefore important to study the impact of lncRNAs in the tumorigenesis of testicular cancer in order to learn how to exploit them in a clinical setting and to substitute more toxic treatments. Eventually, the use of lncRNAs as biomarkers, drug targets, or therapeutics for testicular cancer may represent a valid alternative to that of conventional tools, leading to a better management of this malignancy and its related conditions, and possibly even to the treatment of poor prognosis cases.

Thyrotropin Receptor p.N432D Retained Variant Is Degraded Through an Alternative Lysosomal/Autophagosomal Pathway and Can Be Functionally Rescued by Chemical Chaperones.

Background: Loss-of-function mutations of thyrotropin receptor (TSHR) are one of the main causes of congenital hypothyroidism. As for many disease-associated G-protein coupled receptors (GPCRs), these mutations often affect the correct trafficking and maturation of the receptor, thus impairing the expression on the cell surface. Several retained GPCR mutants are able to effectively bind their ligands and to transduce signals when they are forced to the cell surface by degradation inhibition or by treatment with chaperones. Despite the large number of well-characterized retained TSHR mutants, no attempts have been made for rescue. Further, little is known about TSHR degradation pathways. We hypothesize that, similar to other GPCRs, TSHR retained mutants may be at least partially functional if their maturation and membrane expression is facilitated by chaperones or degradation inhibitors. Methods: We performed in silico predictions of the functionality of known TSHR variants and compared the results with available in vitro data. Western blot, confocal microscopy, enzyme-linked immunosorbent assays, and dual luciferase assays were used to investigate the effects of degradation pathways inhibition and of chemical chaperone treatments on TSHR variants' maturation and functionality. Results: We found a high discordance rate between in silico predictions and in vitro data for retained TSHR variants, a fact indicative of a conserved potential to initiate signal transduction if these mutants were expressed on the cell surface. We show experimentally that some maturation defective TSHR mutants are able to effectively transduce Gs/cAMP signaling if their maturation and expression are enhanced by using chemical chaperones. Further, through the characterization of the intracellular retained p.N432D variant, we provide new insights on the TSHR degradation mechanism, as our results suggest that aggregation-prone mutant can be directed toward the autophagosomal pathway instead of the canonical proteasome system. Conclusions: Our study reveals alternative pathways for TSHR degradation. Retained TSHR variants can be functional when expressed on the cell surface membrane, thus opening the possibility of further studies on the pharmacological modulation of TSHR expression and functionality in patients in whom TSHR signaling is disrupted.

Central hypogonadism in Klinefelter syndrome: report of two cases and review of the literature.

PURPOSE: Klinefelter syndrome (KS) is characterized by late adolescence/young adulthood onset of primary hypogonadism. Hypogonadotropic hypogonadism (HH), when congenital, is usually associated with absent/incomplete puberty and low/normal gonadotropins. We report the clinical and genetic features of two subjects with KS and an unexpected HH hormone profile. METHODS: Magnetic resonance imaging (MRI) of hypothalamus-pituitary region and next generation sequencing (NGS) of congenital HH-associated genes were obtained. A narrative review of the literature was conducted. RESULTS: Patients were diagnosed with Klinefelter syndrome following karyotype analysis. Nevertheless, they showed unusual features: both had incomplete puberty, low gonadotropins and testosterone levels, and the first one was anosmic. Sellar lesions were excluded by MRI, and NGS was negative in both subjects. Our data add to those of the only 14 similar cases reported so far. Unexplained HH rarely occurs in KS and is variably associated with anosmia, other pituitary hormones deficiencies and heterogeneous karyotypes. However, most cases show an early, pre-pubertal onset of hypogonadism. If the causes behind this gonadotropins defect are largely unknown, hereby we provide the first review of the literature on this topic and propose some pathogenetic hypotheses, including the coexistence of KS and congenital HH as suggested by overlapping clinical features in some of these patients. CONCLUSION: HH is an exceptional occurrence in Klinefelter syndrome and is associated with heterogeneous phenotypes and, probably, aetiologies. Moreover, KS could underlie HH nonresponsive to gonadotropins. An exhaustive diagnostic workup and a tailored clinical management are advisable in these rare forms.

Triple-A Syndrome (TAS): An In-Depth Overview on Genetic and Phenotype Heterogeneity.

Triple-A Syndrome (TAS) is a rare autosomal recessive disorder characterized by three cardinal symptoms: alacrimia, achalasia and adrenal insufficiency due to ACTH insensitivity. Various progressive neurological abnormalities and skin changes have been described in association with the syndrome. The disease is caused by mutation in the AAAS gene on chromosome 12q13. Mutations in AAAS were identified in more than 90% of individuals and families with TAS. The protein encoded by AAAS was termed ALADIN and is part of the WD repeat family of proteins, that have been found to be involved in many different functions such as protein-protein interaction, RNA processing, cytoskeleton assembly, control of cell division, signal transduction and apoptosis. Immunohistochemical analysis showed that mutated or truncated ALADIN localizes to the cytoplasm rather than to the nuclear pore complex. The exact function of ALADIN and the mechanisms that lead to the ACTH-resistant adrenal phenotype remains largely unknown. Nonetheless, recent studies provided some insights on the role of ALADIN as a member of the Nuclear Pore Complex not only implicated in the import of proteins involved in DNA repair and oxidative stress homeostasis but also in the strengthening of the mitotic spindle assembly. Early identification of the syndrome is challenging, given the rarity of the condition and high phenotypic heterogeneity even among members of the same family. In this review, we aim to summarize the current knowledge of clinical and molecular profile of patients with TAS and recommendations for the diagnosis, management, and follow-up of patients.

LGR4 deficiency results in delayed puberty through impaired Wnt/ß-catenin signaling.

The initiation of puberty is driven by an upsurge in hypothalamic gonadotropin-releasing hormone (GnRH) secretion. In turn, GnRH secretion upsurge depends on the development of a complex GnRH neuroendocrine network during embryonic life. Although delayed puberty (DP) affects up to 2% of the population, is highly heritable, and is associated with adverse health outcomes, the genes underlying DP remain largely unknown. We aimed to discover regulators by whole-exome sequencing of 160 individuals of 67 multigenerational families in our large, accurately phenotyped DP cohort. LGR4 was the only gene remaining after analysis that was significantly enriched for potentially pathogenic, rare variants in 6 probands. Expression analysis identified specific Lgr4 expression at the site of GnRH neuron development. LGR4 mutant proteins showed impaired Wnt/ß-catenin signaling, owing to defective protein expression, trafficking, and degradation. Mice deficient in Lgr4 had significantly delayed onset of puberty and fewer GnRH neurons compared with WT, whereas lgr4 knockdown in zebrafish embryos prevented formation and migration of GnRH neurons. Further, genetic lineage tracing showed strong Lgr4-mediated Wnt/ß-catenin signaling pathway activation during GnRH neuron development. In conclusion, our results show that LGR4 deficiency impairs Wnt/ß-catenin signaling with observed defects in GnRH neuron development, resulting in a DP phenotype.

Knocking-down of the Prokineticin receptor 2 affects reveals its complex role in the regulation of the hypothalamus-pituitary-gonadal axis in the zebrafish model.

Prokineticin receptors (PROKR1 and PROKR2) are G protein-coupled receptors which control human central and peripheral reproductive processes. Importantly, allelic variants of PROKR2 in humans are associated with altered migration of GnRH neurons, resulting in congenital hypogonadotropic hypogonadism (CHH), a heterogeneous disease characterized by delayed/absent puberty and/or infertility. Although this association is established in humans, murine models failed to fully recapitulate the reproductive and olfactory phenotypes observed in patients harboring PROKR2 mutations. Here, taking advantage of zebrafish model we investigated the role of prokr1b (ortholog of human PROKR2) during early stages of GnRH neuronal migration. Real-Time PCR and whole mount in situ hybridization assays indicate that prokr1b spatial-temporal expression is consistent with gnrh3. Moreover, knockdown and knockout of prokr1b altered the correct development of GnRH3 fibers, a phenotype that is rescued by injection of prokr1b mRNA. These results suggest that prokr1b regulates the development of the GnRH3 system in zebrafish. Analysis of gonads development and mating experiments indicate that prokr1b is not required for fertility in zebrafish, although its loss determine changes also at the testis level. Altogether, our results support the thesis of a divergent evolution in the control of vertebrate reproduction and provide a useful in vivo model for deciphering the mechanisms underlying the effect of PROKR2 allelic variants on CHH.

Publisher Correction: Prokineticin receptor 2 affects GnRH3 neuron ontogeny but not fertility in zebrafish.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Pubertal delay: the challenge of a timely differential diagnosis between congenital hypogonadotropic hypogonadism and constitutional delay of growth and puberty.

Distinguishing between constitutional delay of growth and puberty (CDGP) and congenital hypogonadotropic hypogonadism (CHH) may be challenging. CDGP and CHH appear to belong to the same clinical spectrum (with low sex hormones and low LH and FSH), although one is classically transient and known as a self-limited form of delayed puberty (CDGP) while the other is permanent (CHH). Thus, the clinical history and the outcomes of these two conditions require different approaches, and an adequate and timely management for the patients is mandatory. Since the initial presentation of CDGP and CHH is almost identical and given the similarities of CDGP and partial forms of CHH (i.e. patients with partial and early interrupted pubertal development) the scientific community has been struggling to find some diagnostic tests able to allow an accurate differential diagnosis between these two conditions in delayed puberty. In this review we provide an up to date insight on the tests available, their meanings and accuracy, as well as some clues to effectively differentiate between constitutional pubertal delay and pathologic CHH.

Preclinical and Clinical Evidence for a Distinct Regulation of Mu Opioid and Type 1 Cannabinoid Receptor Genes Expression in Obesity.

Among endogenous signaling networks involved in both rewarding and homeostatic mechanisms of obesity, a relevant role is played by the endocannabinoid (ECS) and the opioid (EOS) systems. We here studied the transcriptional regulation of ECS and EOS genes in the hypothalamus of Diet-induced obesity rats, a preclinical model of obesity, as well as in humans with obesity and healthy controls. A significant and selective increase in type 1 cannabinoid receptor gene (Cnr1) expression was observed at the beginning of obesity development (5 weeks on high fat diet) as well as after 21 weeks of high diet exposure. After 5 weeks on high fat diet, selective up-regulation of mu opioid receptor gene (Oprm1) expression was also observed. Consistently, epigenetic studies showed a selective and significant decrease in DNA methylation at specific CpG sites at both gene promoters in overweight rats, but only after 5 weeks on high fat diet. Moreover, significantly lower levels of DNA methylation were observed at selected CpG sites of both receptor gene promoters, analyzed in peripheral blood mononuclear cells from younger (<30 years old) humans with obesity, as well as in those with shorter time length from disease onset. Taken together, we here provide evidence of selective, synergistic and time-dependent transcriptional regulation of CNR1 and OPRM1 genes in overweight rats, as well as in human subjects. These alterations in genes regulation could contribute to the development of the obese phenotype, and we thus suggest CNR1 and OPRM1 epigenetic modulation as possible biomarkers of obesity development. Due to the reversible nature of the epigenetic hallmark, our data might also open new avenue to early environmental strategies of intervention.

45,X/46,X,i(Yp): Importance of Assessment and Support during Puberty and Adolescence.

The Y-chromosome genes are primarily involved in sex determination, stature control, spermatogenesis, and fertility. Among structural rearrangements of the Y chromosome, the isochromosome of Yp, i(Yp), appears to be the most uncommon. We describe a detailed evolution of puberty in a boy with 45,X/46,X,i(Yp). Array CGH found 2 cell lines, one with i(Yp) and the other with monosomy X. Genetic analysis of currently known genes involved in Kallmann syndrome/normosomic central hypogonadotropic hypogonadism showed no abnormality. The patient presented with a pubertal course suggestive of a delayed puberty with gynecomastia, reduced growth rate, and infertility that need testosterone treatment to induce the appearance of the secondary sex characteristics. This patient shows the potential effects of i(Yp) and emphasizes the importance of appropriate management of puberty in people with 45,X/46,X,i(Yp). Early hormone treatment, concerns regarding fertility, emotional support, and a successful transition to adult care may help improve the physical and psychosocial well-being of affected patients.

High-Density Lipoprotein Function Is Reduced in Patients Affected by Genetic or Idiopathic Hypogonadism.

CONTEXT: Low testosterone levels are associated with an increased incidence of cardiovascular (CV) events, but the underlying biochemical mechanisms are not fully understood. The clinical condition of hypogonadism offers a unique model to unravel the possible role of lipoprotein-associated abnormalities in CV risk. In particular, the assessment of the functional capacities of high-density lipoproteins (HDLs) may provide insights besides traditional risk factors. DESIGN: To determine whether reduced testosterone levels correlate with lipoprotein function, HDL cholesterol (HDL-C) efflux capacity (CEC) and serum cholesterol loading capacity (CLC). PARTICIPANTS: Genetic and idiopathic hypogonadal patients (n = 20) and control subjects (n = 17). RESULTS: Primary and secondary hypogonadal patients presented with lower HDL ATP-binding cassette transporter A1 (ABCA1)-, ATP-binding cassette transporter G1 (ABCG1)-, and aqueous diffusion-mediated CEC (-19.6%, -40.9%, and -12.9%, respectively), with a 16.2% decrement of total CEC. In the whole series, positive correlations between testosterone levels and both total HDL CEC (r2 = 0.359, P = 0.0001) and ABCG1 HDL CEC (r2 = 0.367, P = 0.0001) were observed. Conversely, serum CLC was markedly raised (+43%) in hypogonadals, increased, to a higher extent, in primary vs secondary hypogonadism (18.45 ± 2.78 vs 15.15 ± 2.10 µg cholesterol/mg protein) and inversely correlated with testosterone levels (r2 = 0.270, P = 0.001). HDL-C concentrations did not correlate with either testosterone levels, HDL CEC (total, ABCG1, and ABCA1) or serum CLC. CONCLUSIONS: In hypogonadal patients, proatherogenic lipoprotein-associated changes are associated with lower cholesterol efflux and increased influx, thus offering an explanation for a potentially increased CV risk.

Evidence for a Common Genetic Origin of Classic and Milder Adult-Onset Forms of Isolated Hypogonadotropic Hypogonadism.

Multiple metabolic and inflammatory mechanisms are considered the determinants of acquired functional isolated hypogonadotropic hypogonadism (IHH) in males, whereas classic IHH is a rare congenital condition with a strong genetic background. Since we recently uncovered a frequent familiarity for classic IHH among patients with mild adult-onset hypogonadism (AO-IHH), here we performed a genetic characterization by next generation sequencing of 160 males with classic or "functional" forms. The prevalence of rare variants in 28 candidate genes was significantly higher than in controls in all IHH patients, independently of the age of IHH onset, degree of hypogonadism or presence of obesity. In fact, it did not differ among patients with classic or milder forms of IHH, however particular genes appear to be more specifically associated with one or the other category of IHH. ROC curves showed that Total Testosterone <6.05 nmol/L and an age of onset <41 years are sensitive cutoffs to identify patients with significantly higher chances of harboring rare IHH gene variants. In conclusion, rare IHH genes variants can frequently predispose to AO-IHH with acquired mild hormonal deficiencies. The identification of a genetic predisposition can improve the familial and individual management of AO-IHH and explain the heritability of congenital IHH.

Characteristics of a nationwide cohort of patients presenting with isolated hypogonadotropic hypogonadism (IHH).

OBJECTIVE: Isolated hypogonadotropic hypogonadism (IHH) is a rare disorder with pubertal delay, normal (normoosmic-IHH, nIHH) or defective sense of smell (Kallmann syndrome, KS). Other reproductive and non-reproductive anomalies might be present although information on their frequency are scanty, particularly according to the age of presentation. DESIGN: Observational cohort study carried out between January 2008 and June 2016 within a national network of academic or general hospitals. METHODS: We performed a detailed phenotyping of 503 IHH patients with: (1) manifestations of hypogonadism with low sex steroid hormone and low/normal gonadotropins; (2) absence of expansive hypothalamic/pituitary lesions or multiple pituitary hormone defects. Cohort was divided on IHH onset (PPO, pre-pubertal onset or AO, adult onset) and olfactory function: PPO-nIHH (n = 275), KS (n = 184), AO-nIHH (n = 36) and AO-doIHH (AO-IHH with defective olfaction, n = 8). RESULTS: 90% of patients were classified as PPO and 10% as AO. Typical midline and olfactory defects, bimanual synkinesis and familiarity for pubertal delay were also found among the AO-IHH. Mean age at diagnosis was significantly earlier and more frequently associated with congenital hypogonadism stigmata in patients with Kallmann's syndrome (KS). Synkinesis, renal and male genital tract anomalies were enriched in KS. Overweight/obesity are significantly associated with AO-IHH rather than PPO-IHH. CONCLUSIONS: Patients with KS are more prone to develop a severe and complex phenotype than nIHH. The presence of typical extra-gonadal defects and familiarity for PPO-IHH among the AO-IHH patients indicates a common predisposition with variable clinical expression. Overall, these findings improve the understanding of IHH and may have a positive impact on the management of patients and their families.