Prioritizing genetic testing in patients with Kallmann syndrome using clinical phenotypes

Clinical manifestations and spermatogenesis outcomes in Chinese patients with congenital hypogonadotropic hypogonadism caused by inherited or de novo FGFR1 mutations

Fibroblast growth factor receptor 1 ( FGFR1 ) mutations are associated with congenital hypogonadotropic hypogonadism (CHH) through inheritance or spontaneous occurrence. We detected FGFR1 mutations in a Chinese cohort of 210 CHH patients at Peking Union Medical College Hospital (Beijing, China) using next-generation and Sanger sequencing. We assessed missense variant pathogenicity using six bioinformatics tools and compared clinical features and treatment outcomes between inherited and de novo mutation groups. Among 19 patients with FGFR1 mutations, three were recurrent, and 16 were novel variants. Sixteen of the novel mutations were likely pathogenic according to the American College of Medical Genetics and Genomics (ACMG) guidelines, with the prevalent P366L variant. The majority of FGFR1 mutations was inherited (57.9%), with frameshift mutations exclusive to the de novo mutation group. The inherited mutation group had a lower incidence of cryptorchidism, short stature, and skeletal deformities. In the inherited mutation group, luteinizing hormone (LH) levels were 0.5 IU l -1 , follicle-stimulating hormone (FSH) levels were 1.0 IU l -1 , and testosterone levels were 1.3 nmol l -1 . In contrast, the de novo group had LH levels of 0.2 IU l -1 , FSH levels of 0.5 IU l -1 , and testosterone levels of 0.9 nmol l -1 , indicating milder hypothalamus-pituitary-gonadal axis (HPGA) functional deficiency in the inherited group. The inherited mutation group showed a tendency toward higher spermatogenesis rates. In conclusion, this study underscores the predominance of inherited FGFR1 mutations and their association with milder HPGA dysfunction compared to de novo mutations, contributing to our understanding of the genetic and clinical aspects of FGFR1 mutations.

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 multifaceted links between hearing loss and chronic kidney disease

Hearing loss affects nearly 1.6 billion people and is the third-leading cause of disability worldwide. Chronic kidney disease (CKD) is also a common condition that is associated with adverse clinical outcomes and high health-care costs. From a developmental perspective, the structures responsible for hearing have a common morphogenetic origin with the kidney, and genetic abnormalities that cause familial forms of hearing loss can also lead to kidney disease. On a cellular level, normal kidney and cochlea function both depend on cilial activities at the apical surface, and kidney tubular cells and sensory epithelial cells of the inner ear use similar transport mechanisms to modify luminal fluid. The two organs also share the same collagen IV basement membrane network. Thus, strong developmental and physiological links exist between hearing and kidney function. These theoretical considerations are supported by epidemiological data demonstrating that CKD is associated with a graded and independent excess risk of sensorineural hearing loss. In addition to developmental and physiological links between kidney and cochlear function, hearing loss in patients with CKD may be driven by specific medications or treatments, including haemodialysis. The associations between these two common conditions are not commonly appreciated, yet have important implications for research and clinical practice.

Additional mutation in PROKR2 and phenotypic differences in a Kallmann syndrome/normosmic congenital hypogonadotropic hypogonadism family carrying FGFR1 missense mutation

Congenital hypogonadotropic hypogonadism (CHH) is a genetically and clinically diverse disorder encompassing Kallmann syndrome (KS) and normosmic CHH (nCHH). Although mutations in numerous genes account for nearly 50% of CHH cases, a significant portion remains genetically uncharacterized. While most mutations follow the traditional Mendelian inheritance patterns, evidence suggests oligogenic interactions between CHH genes, acting as modifier genes to explain variable expressivity and incomplete penetrance associated with certain mutations.In this study, the proband presented with nCHH, while his son exhibited KS. We employed whole-exome sequencing (WES) to investigate the genetic differences between the two, and Sanger sequencing was used to validate the results obtained from WES.Genetic analysis revealed that both the proband and his son harboured a mutation in FGFR1 gene. Notably, an additional rare mutation in PROKR2 gene was exclusively identified in the son, which suggests the cause of the phenotypic difference between KS and nCHH.

[Research progress on hereditary endocrine and metabolic diseases associated with sensorineural hearing loss]

Hereditary endocrine and metabolic diseases , caused by genetic factors, exhibit complex and diverse symptoms, including the possibility of concurrent sensorineural deafness. Currently, there is a limited clinical understanding of hereditary endocrine and metabolic diseases that manifest with deafness, the pathogenesis remains unclear,and there is a lack of effective diagnostic and treatment methods. This article summarizes the research progress of hereditary endocrine and metabolic diseases complicated with deafness from the pathogenesis, clinical phenotype, diagnosis and treatment. Understanding the current research progress and integrating genetic analysis into clinical practice are crucial for accurate diagnosis and treatment, evaluating clinical efficacy, and providing effective genetic counseling for these diseases.

Case Report: Multiple prolactinomas in a young man with Kallmann syndrome and familial hypocalciuric hypercalcemia

Introduction

The occurrence of prolactinomas in sex hormone treated patients with central hypogonadism is extremely rare.

Case presentation

We present a Caucasian male patient who was diagnosed with Kallmann syndrome (KS) at age 15 years. Testosterone treatment was started. At age 26 the patient presented with mild headache. MRI revealed two separate pituitary adenomas along with the absence of the olfactory bulbs. Given the presence of marked hyperprolactinemia (17x upper limit of the reference range) the diagnosis prolactinoma was made and treatment with cabergoline was started which resulted in a complete biochemical response and in marked reduction of both adenomas in size. Hypogonadism persisted and testosterone replacement therapy was continued. Genetic testing of genes associated with pituitary tumors, Kallmann syndrome and idiopathic hypogonadotropic hypogonadism was negative. Mild concomitant hypercalcemia in accordance with familial hypocalciuric hypercalcemia (FHH) prompted mutation analysis of the calcium receptor (CASR) gene which yielded a pathogenic inactivating variant.

Discussion/conclusion

The presence of two separate prolactinomas in a patient with KS has not yet been reported in the literature. The effect of sex hormone treatment of KS patients on the possible development of prolactinoma is unknown at present. The occurance of multiple prolactinomas in our patient suggests increased susceptibility. Although CaSR is expressed in GnRH neurons in mouse brain and CaSR deficient mice have a reduced hypothalamic GnRH neuronal population, the relevance of the CASR gene variant in our patient for the KS phenotype is unclear at present.

Cases of hypogonadotropic hypogonadism: A single-center experience

Background

Delayed puberty (DP) affects approximately 2% of adolescents. In most patients of both genders, delayed puberty is due to constitutional delay in growth and puberty (CDGP); it is a self-limiting condition starting later than usual during puberty but progressing normally. Other causes of DP include permanent hypogonadotropic hypogonadism, functional hypogonadotropic hypogonadism, and gonadal insufficiency.

Methods

Nine patients admitted to the Ankara Atatürk Sanatoryum Training and Research Hospital Pediatric Endocrinology Department with hypogonadotropic hypogonadism between January 2012 and December 2022 were analyzed.

Results

Nine patients who applied to our pediatric endocrinology clinic with delayed puberty were analyzed. These nine patients were diagnosed and reported as hypogonadotropic hypogonadism with molecular methods. We aimed to determine the status of these cases from a molecular point of view, to emphasize the importance of hypogonadotropic hypogonadism in patients with delayed puberty, and to reveal the rarely encountered delayed puberty together with the clinical and laboratory data set of the patients.

Conclusions

To emphasize the importance of hypogonadotropic hypogonadism, which is a rare cause of delayed puberty, the molecular predispositions of our patients followed in our clinic are reviewed, and the data we have provided will contribute to the accumulation of data in this area.

A functional spectrum of PROKR2 mutations identified in isolated hypogonadotropic hypogonadism

Isolated hypogonadotropic hypogonadism (IHH) is a rare disease with hypogonadism and infertility caused by the defects in embryonic migration of hypothalamic gonadotropin-releasing hormone (GnRH) neurons, hypothalamic GnRH secretion or GnRH signal transduction. PROKR2 gene, encoding a G-protein coupled receptor PROKR2, is one of the most frequently mutated genes identified in IHH patients. However, the functional consequences of several PROKR2 mutants remain elusive. In this study, we systematically analyzed the Gαq, Gαs and ERK1/2 signaling of 23 IHH-associated PROKR2 mutations which are yet to be functionally characterized. We demonstrate that blockage of Gαq, instead of MAPK/ERK pathway, inhibited PROK2-induced migration of PROKR2-expressing cells, implying that PROKR2-related IHH results primarily due to Gαq signaling pathway disruption. Combined with previous reports, we categorized a total of 63 IHH-associated PROKR2 mutations into four distinct groups according Gαq pathway functionality: (i) neutral (N, >80% activity); (ii) low pathogenicity (L, 50-80% activity); (iii) medium pathogenicity (M, 20-50% activity) and (iv) high pathogenicity (H, <20% activity). We further compared the cell-based functional results with in silico mutational prediction programs. Our results indicated that while Sorting Intolerant from Tolerant predictions were accurate for transmembrane region mutations, mutations localized in the intracellular and extracellular domains were accurately predicted by the Combined Annotation Dependent Depletion prediction tool. Our results thus provide a functional database that can be used to guide diagnosis and appropriate genetic counseling in IHH patients with PROKR2 mutations.

Reproductive Phenotypes and Genotypes in Men With IHH

CONTEXT

Isolated hypogonadotropic hypogonadism (IHH) is phenotypically and genetically heterogeneous.

OBJECTIVE

This work aimed to determine the correlation between genotypic severity with pubertal and neuroendocrine phenotypes in IHH men.

METHODS

A retrospective study was conducted (1980-2020) examining olfaction (Kallmann syndrome [KS] vs normosmic IHH [nHH]), baseline testicular volume (absent vs partial puberty), neuroendocrine profiling (pulsatile vs apulsatile luteinizing hormone [LH] secretion), and genetic variants in 62 IHH-associated genes through exome sequencing (ES).

RESULTS

In total, 242 men (KS: n = 131 [54%], nHH: n = 111 [46%]) were included. Men with absent puberty had significantly lower gonadotropin levels (P < .001) and were more likely to have undetectable LH (P < .001). Logistic regression showed partial puberty as a statistically significant predictor of pulsatile LH secretion (R2 = 0.71, P < .001, OR: 10.8; 95% CI, 3.6-38.6). Serum LH of 2.10 IU/L had a 95% true positive rate for predicting LH pulsatility. Genetic analyses in 204 of 242 IHH men with ES data available revealed 36 of 204 (18%) men carried protein-truncating variants (PTVs) in 12 IHH genes. Men with absent puberty and apulsatile LH were enriched for oligogenic PTVs (P < .001), with variants in ANOS1 being the predominant PTV in this genotype-phenotype association. Men with absent puberty were enriched for ANOS1 PTVs compared to partial puberty counterparts (P = .002). PTVs in other IHH genes imparted more variable reproductive phenotypic severity.

CONCLUSION

Partial puberty and LH greater than or equal to 2.10 IU/L are proxies for pulsatile LH secretion. ANOS1 PTVs confer severe reproductive phenotypes. Variable phenotypic severity in the face of severe genetic variants in other IHH genes point to significant neuroendocrine plasticity of the HPG axis in IHH men.

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.

Phenotypic and genotypic landscape of PROKR2 in neuroendocrine disorders

Prokineticin receptor 2 (PROKR2) encodes for a G-protein-coupled receptor that can bind PROK1 and PROK2. Mice lacking Prokr2 have been shown to present abnormal olfactory bulb formation as well as defects in GnRH neuron migration. Patients carrying mutations in PROKR2 typically present hypogonadotropic hypogonadism, anosmia/hyposmia or Kallmann Syndrome. More recently variants in PROKR2 have been linked to several other endocrine disorders. In particular, several patients with pituitary disorders have been reported, ranging from mild phenotypes, such as isolated growth hormone deficiency, to more severe ones, such as septo-optic dysplasia. Here we summarize the changing landscape of PROKR2-related disease, the variants reported to date, and discuss their origin, classification and functional assessment.

Genetic spectrum of Kallmann syndrome: Single-center experience and systematic review

OBJECTIVE

To study phenotype-genotype data of Asian-Indian Kallmann syndrome (KS) from our center and systematically review the studies analyzing multiple congenital hypogonadotropic hypogonadism (CHH) genes in KS cohorts using next-generation sequencing.

DESIGN, PATIENTS, MEASUREMENT

Five hundred twenty-two KS probands (our center n = 78, published studies n = 444) were included in this systematic review. Molecular diagnosis was considered if the likely pathogenic/pathogenic variant in known CHH gene/s was reported in the appropriate allelic state. Varsome prediction tool (following American College of Medical Genetics standards) was used to analyze the variants.

RESULT

For our center, the molecular diagnosis was seen in 20.5% of probands and was seen more often with severe than partial reproductive phenotype (28.3% vs. 4%, p = .0013). Our center data adds eight novel variants. The molecular diagnosis was seen in 31% as per the systematic review and analysis. It ranged from 16.6% to 72.2% at different centers. The affected genes were FGFR1 (9.8%), ANOS1 (7.5%), PROKR2 (6.1%), CHD7 (5.4%), oligogenic (2.1%), and others &lt;1% each (FGF8, SOX10, PROK2, SEMA3A, IL17RD, and GNRHR). FGFR1 and ANOS1 were the commonly affected genes globally, whereas PROKR2 was commonest in studies from China and CHD7 from Japan, South Korea and Poland.

CONCLUSION(S)

This systematic review highlights that the genetic yield is 31% in KS probands, with distinct regional variations. The association of severe reproductive phenotype with the higher genetic yield needs further validation.

Identification of a novel mutation in FGFR1 gene in mother and daughter with Kallmann syndrome

OBJECTIVES

Congenital hypogonadotropic hypogonadism combined with anosmia or hyposmia is considered Kallmann syndrome (KS). It is often accompanied by bone defects.

CASE PRESENTATION

Here, we report a girl and her mother with KS caused by a novel mutation in the fibroblast growth factor receptor 1 gene (FGFR1). Interestingly, the daughter presented syndactyly and oligodactyly of the feet.

CONCLUSIONS

The presence of bone malformations in a KS patient should direct the geneticist towards a search for specific mutations in FGFR1. Our finding contributes to enrich the spectrum of FGFR1 mutations in patients with KS.

The Clinical and Genetic Characteristics in Children with Idiopathic Hypogonadotropin Hypogonadism

Background. Idiopathic hypogonadotropin hypogonadism (IHH) is caused by hypothalamic-pituitary-gonadal axis dysfunction. This is divided into Kallmann syndrome which has an impaired sense of smell and hypogonadotropin hypogonadism with normal olfactory (nIHH sense. Approximately 60% of patients are associated with Kallmann syndrome, whereas there are approximately 40% with hypogonadotropin hypogonadism (nIHH). This disease is associated with various variants in genes along with different phenotypic characteristics, and even those gene variations could also lead to the cancer formation in patients. So, current study has been designed to investigate and to better understand the characteristics of various IHH-associated genes and the correlation between IHH genes and phenotype. Methods. The cohort included 14 children with IHH (6 patients of KS and 8 patients of IHH), including 13 boys and 1 girl. Exclusion criteria are as follows: diagnosis of secondary hypogonadotropin hypogonadism due to tumor, trauma, drugs, or other systemic diseases. Clinical data and genetic results were analyzed. Results. Almost all male patients showed micropenis (12/13, 92.3%), and few of them had cryptorchidism (5/13, 41.7%). A total of 6 genes, CHD7, PROKR2, ANOS1, FGFR1, SEMA3A, and NDNF, were detected. CHD7 was the most common (11/17, 64.7%), and the main mutation type was missense mutation (14/16, 87.5%). Six reported variants and 10 new variants (5 genes, including entire ANSO1 duplicates) were found. Neonatal variation was detected in 3 patients with IHH. Eight patients inherited the variation from their father, while five patients inherited it from their mother. One patient had both FGFR1 and SEMA3A gene variants, while the other had two different CHD7 gene variants and entire ANSO1 repeats. According to ACMG criteria, 4 variants were pathogenic (P), 2 were possibly pathogenic (LP), and 8 had uncertain significance (US). In patients with P or LP (5/6, 83.3%), we found that extragonadal symptoms were more common. Conclusions. It was concluded that variations in the studied genes could lead to the IHH. Ten new variants have been reported which may lead to different symptoms of IHH. For CHD7 variants, the rare sequencing variants (RSVs) of P or LP showed commonly associated with CHARGE syndrome. Findings of the current study may help for the better diagnosis and treatment of IHH.

ANOS1 variants in a large cohort of Chinese patients with congenital hypogonadotropic hypogonadism

OBJECTIVES

Congenital hypogonadotropic hypogonadism (CHH) is a rare congenital gonadal dysplasia caused by defects in the synthesis, secretion or signal transduction of hypothalamic gonadotropin releasing hormone. The main manifestations of CHH are delayed or lack puberty, low levels of sex hormones and gonadotropins, and may be accompanied with other clinical phenotypes. Some patients with CHH are also accompanied with anosmia or hyposmia, which is called Kalman syndrome (KS). ANOS1, located on X chromosome, is the first gene associated with CHH in an X-linked recessive manner. This study aims to provide a basis for the genetic diagnosis of CHH by analyzing the gene variant spectrum of ANOS1 in CHH and the relationship between clinical phenotype and genotype.

METHODS

In this study, whole exome sequencing (WES) was used to screen rare sequencing variants (RSVs) of ANOS1 in a Chinese cohort of 165 male CHH patients. Four commonly used in silico tools were used to predict the function of the identified RSVs in coding region, including Polyphen2, Mutation Taster, SIFT, and Combined Annotation Dependent Depletion (CADD). Splice Site Prediction by Neural Network (NNSPLICE) was employed to predict possibilities of intronic RSVs to disrupt splicing. American College of Medical Genetics and Genomics (ACMG) guidelines was used to assess the pathogenicity of the detected RSVs. The ANOS1 genetic variant spectrum of CHH patients in Chinese population was established. The relationship between clinical phenotype and genotype was analyzed by collecting detailed clinical data.

RESULTS

Through WES analysis for 165 CHH patients, ANOS1 RSVs were detected in 17 of them, with the frequency of 10.3%. A total of 13 RSVs were detected in the 17 probands, including 5 nonsense variants (p.T76X, p.R191X, p.W257X, p.R262X, and p.W589X), 2 splicing site variants (c.318+3A>C, c.1063-1G>C), and 6 missense variants (p.N402S, p.N155D, p.P504L, p.C157R, p.Q635P, and p.V560I). In these 17 CHH probands with ANOS1 RSVs, many were accompanied with other clinical phenotypes. The most common associated phenotype was cryptorchidism (10/17), followed by unilateral renal agenesis (3/17), dental agenesis (3/17), and synkinesia (3/17). Eight RSVs, including p.T76X, p.R191X, p.W257X, p.R262X, p.W589X, c.318+3A>C, c.1063-1G>C, and p.C157R, were predicted to be pathogenic or likely pathogenic ANOS1 RSVs by ACMG. Eight CHH patients with pathogenic or likely pathogenic ANOS1 variants had additional features. In contrast, only one out of nine CHH patients with non-pathogenic (likely benign or uncertain of significance) ANOS1 variants according to ACMG exhibited additional features. And function of the non-pathogenic ANOS1 variants accompanied with other CHH-associated RSVs.

CONCLUSIONS

The ANOS1 genetic spectrum of CHH patients in Chinese population is established. Some of the correlations between clinical phenotype and genotype are also established. Our study indicates that CHH patients with pathogenic or likely pathogenic ANOS1 RSVs tend to exhibit additional phenotypes. Although non-pathogenic ANOS1 variants only may not be sufficient to cause CHH, they may function together with other CHH-associated RSVs to cause the disease.

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.

Two Sisters with Kallmann Syndrome, Gonadal Dysgenesis, and Multiple Neuromuscular and Endocrine Disorders: Report of Two Cases with Description of an Unusual Association

Kallmann syndrome (KS) is an uncommon genetic disorder characterized by isolated congenital hypogonadotropic hypogonadism (CHH) and anosmia/hyposmia. KS originates from abnormal embryonic migration of olfactory axons and gonadotropin-releasing hormone (GnRH)-synthesizing neurons. It can be challenging to diagnose due to its heterogeneous clinical presentation and genes implied. Herein, we report a rare phenotype of KS in two sisters accompanied by a variety of nonreproductive disorders such as hypoparathyroidism, hypercortisolism, atrophy of the cerebellum, intellectual disability, and remarkably, ovarian dysgenesis. Additionally, both subjects present muscle weakness, exercise intolerance, marked hypotonia and seizures, being suspected, although not fully confirmed, mitochondrial encephalomyopathy. These cases illustrate the heterogeneous clinical presentation and the diagnostic difficulties often found in patients suffering from this condition. These clinical features have never been described before as associated with KS; therefore, we decided to report this novel KS phenotype.

Clinical, hormonal, and genetic characteristics of 25 Chinese patients with idiopathic hypogonadotropic hypogonadism

BACKGROUND

Idiopathic hypogonadotropic hypogonadism (IHH) is a type of congenital disease caused by a variety of gene variants leading to dysfunction in the secretion of hypothalamic gonadotropin-releasing hormones (GnRHs). Clinically, IHH can be divided into Kallmann syndrome (KS) with dysosmia and normosmic idiopathic hypogonadotropic hypogonadism (nIHH) according to the presence or absence of an olfactory disorder.

METHODS

We retrospectively evaluated 25 IHH patients (8 KS and 17 nIHH) who were diagnosed at the Department of Endocrinology of Shanghai Children's Hospital from 2015 to 2021. We analysed the patients' clinical data, including their hormone levels and gene sequences.

RESULTS

All male patients exhibited small phalli, and 35% of them exhibited cryptorchidism. A significant difference was observed in the levels of dihydrotestosterone (DHT) after human chorionic gonadotropin (HCG) stimulation (P = 0.028) between the KS group and the nIHH group. Missense variants were the major cause of IHH, and the main pathogenic genes were FGFR1, PROKR2/PROK2, and KAl1. Nine reported and 13 novel variants of six genes were identified. De novo variants were detected in 16 IHH patients; eight patients inherited the variants from their mothers, while only three patients inherited variants from their fathers. One patient had both KAl1 and PROKR2 gene variants, and another patient had two different PROKR2 gene variants. These two patients both had the hot spot variant c.533G > C (p. Trp178Ser) of the PROKR2 gene.

CONCLUSION

IHH should be highly suspected in patients with a small phallus and cryptorchidism. Compared with nIHH patients, KS patients exhibited a higher level of DHT after HCG stimulation. Missense variants were the major cause of IHH, and most of the inherited variants were from their mothers who exhibited no obvious clinical symptoms. We identified 9 reported variants and 13 novel variants that led to IHH. A small proportion of patients were at risk of inheriting either the oligogenic variant or the compound heterozygous variant. The hot spot variant c.533G > C (p. Trp178Ser) of PROKR2 might be involved in oligogenic inheritance and compound heterozygous inheritance. These findings provide deeper insight into the diagnosis and classification of IHH and will contribute to its clinical assessment.

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.

A novel heterozygous mutation of CHD7 gene in a Chinese patient with Kallmann syndrome: a case report

BACKGROUND

Variants of chromodomain helicase DNA binding protein 7 (CHD7) gene are commonly associated with Kallmann syndrome (KS) and account for 5-6% of idiopathic hypogonadotropic hypogonadism (IHH) cases. Here we report a novel mutation of CHD7 gene in a patient with KS, which may contribute to the better understanding of KS.

CASE PRESENTATION

A 29-year-old male patient with KS and a chief complaint of delayed puberty for 13 years (Tanner B Stage< 4) was admitted to the Department of Endocrinology of the First Affiliated Hospital of Zhejiang University (Hangzhou, China) in September 2019. Dual-energy X-ray absorptiometry (DEXA) showed low bone density in both lumbar spine (L1 ~ L5 mean Z-score - 3.0) and femoral neck (Z-score - 2.7). Dynamic contrast-enhanced magnetic resonance imaging (MRI) of pituitary and contrast-enhanced computed tomography (CT) showed no abnormal findings. Ophthalmological evaluation showed that his both eyes showed exotropia, and no sight loss was noted. Heterozygous c.1619G > T mutation of TCD7 gene (p.G4856V) was detected, whereas none of his family members had this mutation. Human chorionic gonadotropin (HCG) and human menopausal gonadotropin (HMG) were injected for three times/week to treat idiopathic hypogonadotropic hypogonadism (IHH). After several months of therapy, the patient's health condition improved. His testicles became larger, and his secondary sexual characteristics improved after treatment.

CONCLUSION

Exploration of the novel splice-site mutation of CHD7 may further our current understanding of KS.

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.

[Molecular genetics and phenotypic features of congenital isolated hypogonadotropic hypogonadism]

Congenital isolated hypogonadotropic hypogonadism includes a group of diseases related to the defects of secretion and action of gonadotropin-releasing hormone (GNRH) and gonadotropins. In a half of cases congenital hypogonadism is associated with an impaired sense of smell. It's named Kallmann syndrome. Now 40 genes are known to be associated with function of hypothalamus pituitary gland and gonads. Phenotypic features of hypogonadism and therapy effectiveness are related to different molecular defects. However clinical signs may vary even within the same family with the same molecular genetic defect. Genotype phenotype correlation in patients with congenital malformations prioritizes the search for mutations in candidate genes. There are data of significant contribution of oligogenicity into the phenotype of the disease are presented in the review. Moreover, an issue of current isolated hypogonadotropic hypogonadism definition and classification revision is raised in the review due to hypogonadotropic hypogonadism development while there are mutations in genes not associated with GNRH neurons secretion and function.

Genetic Profiles and Three-year Follow-up Study of Chinese Males With Congenital Hypogonadotropic Hypogonadism

BACKGROUND

The correlation between long-term treatment outcomes with genotypes in congenital hypogonadotropic hypogonadism (CHH) males is rarely reported.

AIM

To investigate the correlations among genotypes, phenotypes, and treatment outcomes for CHH male patients.

METHODS

Whole exome sequencing was performed for 73 Chinese CHH males from one academic center. Patients self-selected one of the 4 treatments: pulsatile Gonadorelin pump (PGP), cyclical gonadotropins therapy (CGT), human menopausal gonadotropin monotherapy, or testosterone replacement treatment. Clinical assessments were performed every 3 months for 3 years.

OUTCOMES

The pathogenicity of variants was determined. Baseline clinical features, spermatogenesis outcomes were analysed.

RESULTS

62 variants were identified in 51 patients (69.9%), 17 of which were novel. Among these mutations, variants on FGFR1, PROKR2, CHD7, ANOS1 and NSMF gene were 16.1%, 16.1%, 11.3%, 8.1% and 8.1% respectively. 11 patients followed the oligogenic pattern (21.6%). All CHD7 patients had hearing impairment, or structural deformities of external/ inner ear and were diagnosed as CHARGE syndrome. 24.7% of CHH patients manifested with ear/hearing anomalies. KS patients had higher rates of cryptorchidism history and ear/hearing anomalies than normosmic CHH subjects. Male patients with PROKR2 mutations showed relatively better testicular development, less dental deformity when compared with FGFR1 mutations. About 30% normosmic patients defined by simple olfactory assessment showed olfactory nerve center (ONC) dysplasia under nasal sinus MRI examination. Among the CHH males treated with CGT or PGP, 70.2% reached spermatogenesis within 3 years of treatment.

CLINICAL IMPLICATIONS

No direct correlation was observed between certain responsible genes and spermatogenic outcomes. When CHH patients were identified with CHD7 variants, ear/hearing evaluation should be carefully performed. The precise assessment of ONC development was advised for normosmic CHH subjects.

STRENGTHS & LIMITATIONS

This study provided informative long-term treatment data of CHH male patients screened with whole exome sequencing. The limitations included small number of subgroups with multifaceted gene variants, clinical heterogeneity, uncontrolled sperm-inducing treatment method. The seventeen novel mutations worth experimental validation in the future.

CONCLUSION

The clinical severity is partially related with specific gene variants, and detailed individualized data and outcomes were provided. Ear/hearing anomalies were closely connected with CHD7 variants, and were common problems for CHH patients. Simple olfactory assessment underestimated the true olfactory deficit. L. Zhang, Y. Gao, Q. Du, et al. Genetic Profiles and Three-year Follow-up Study of Chinese Males With Congenital Hypogonadotropic Hypogonadism. J Sex Med 2021;XX:XXX-XXX.

Mechanisms of Central Hypogonadism

Reproductive function depends upon an operational hypothalamo–pituitary–gonadal (HPG) axis. Due to its role in determining survival versus reproductive strategies, the HPG axis is vulnerable to a diverse plethora of signals that ultimately manifest with Central Hypogonadism (CH) in all its many guises. Acquired CH can result from any pituitary or hypothalamic lesion, including its treatment (such as surgical resection and/or radiotherapy). The HPG axis is particularly sensitive to the suppressive effects of hyperprolactinaemia that can occur for many reasons, including prolactinomas, and as a side effect of certain drug therapies. Physiologically, prolactin (combined with the suppressive effects of autonomic neural signals from suckling) plays a key role in suppressing the gonadal axis and establishing temporary CH during lactation. Leptin is a further key endocrine regulator of the HPG axis. During starvation, hypoleptinaemia (from diminished fat stores) results in activation of hypothalamic agouti-related peptide neurons that have a dual purpose to enhance appetite (important for survival) and concomitantly suppresses GnRH neurons via effects on neural kisspeptin release. Obesity is associated with hyperleptinaemia and leptin resistance that may also suppress the HPG axis. The suppressibility of the HPG axis also leaves it vulnerable to the effects of external signals that include morphine, anabolic-androgenic steroids, physical trauma and stress, all of which are relatively common causes of CH. Finally, the HPG axis is susceptible to congenital malformations, with reports of mutations within >50 genes that manifest with congenital CH, including Kallmann Syndrome associated with hyposmia or anosmia (reduction or loss of the sense of smell due to the closely associated migration of GnRH with olfactory neurons during embryogenesis). Analogous to the HPG axis itself, patients with CH are often vulnerable, and their clinical management requires both sensitivity and empathy.

Advances in Genetic Diagnosis of Kallmann Syndrome and Genetic Interruption

Kallmann syndrome (KS) is a rare hereditary disease with high phenotypic and genetic heterogeneity. Congenital hypogonadotropic hypogonadism and hyposmia/anosmia are the two major characterized phenotypes of KS. Besides, mirror movements, dental agenesis, digital bone abnormalities, unilateral renal agenesis, midline facial defects, hearing loss, and eye movement abnormalities can also be observed in KS patients. Because of the phenotypic heterogeneity, genetic diagnosis become increasingly valuable to distinguish KS from other disorders including normosmic congenital hypogonadotropic hypogonadism, constitutional delay of growth and puberty, CHARGE syndrome, and functional hypogonadotropic hypogonadism. Application of next-generation sequencing has promoted the discovery of novel pathogenic genes in KS pedigrees. Prenatal diagnosis is an effective method in clinical settings to decrease birth defects and block transmission of genetic disorders. However, pregnant women may suffer from physical and psychological distress when fetuses are diagnosed with congenital defects. Preimplantation genetic testing (PGT) is a prospective approach during the in vitro fertilization process that helps to interrupt transmission of hereditary diseases to offspring at an early stage. Thus, genetic testing and counseling are recommended to KS patients with family histories, prenatal diagnosis and PGT are considered to be useful options.

Clinical characteristics and molecular genetic analysis of a cohort with idiopathic congenital hypogonadism

OBJECTIVES

Hypogonadism is defined as inadequate sex hormone production due to defects in the hypothalamic-pituitary-gonadal axis. In recent years, rare single gene defects have been identified in both hypergonadotropic hypogonadism (Hh), and hypogonadotropic hypogonadism (HH) cases with no chromosomal anomalies. The aim of the present study is to investigate the underlying molecular genetic etiology and the genotype-phenotype relationship of a series of patients with Hh and HH.

METHODS

In total, 27 HH and six Hh cases were evaluated. Clinical and laboratory features are extracted from patients' hospital files. Whole exome sequencing (WES) analysis was performed.

RESULTS

A total of 27 HH cases (15 female) (mean age: 15.8 ± 2.7 years) and six Hh patients (six females) (mean age: 14.9 ± 1.2 years) were included. In molecular genetic analysis, a pathogenic/likely pathogenic variant was identified in five (two patients from the same family) of 27 HH cases (two novel) and three of the six Hh. In HH group variants (pathogenic, likely pathogenic and variant of uncertain significance) were identified in KISS1R (n=2), PROK2 (n=1), FGFR1 (n=1), HS6ST1 (n=1), GNRH1 (n=1) genes. In the Hh group, splice-site mutations were detected in DCAF17 (n=1) and MCM9 (n=2) genes.

CONCLUSIONS

HH and Hh cases are genetically heterogeneous diseases due to oligogenic inheritance, incomplete penetrance, and variable expressivity. We found rare variants in CHH related genes in half of our HH cases, whereas they classified as pathogenic/likely pathogenic according to ACMG criteria in only about 15% of HH cases. Using advanced genetic analysis methods such as whole-genome sequencing and long-read sequencing may increase the mutation detection rate, which should always be associated with and expert genetic counseling to interpret the data.

Defects in GnRH Neuron Migration/Development and Hypothalamic-Pituitary Signaling Impact Clinical Variability of Kallmann Syndrome

Kallmann syndrome (KS) is a combination of isolated hypogonadotropic hypogonadism (IHH) with olfactory dysfunction, representing a heterogeneous disorder with a broad phenotypic spectrum. The genetic background of KS has not yet been fully established. This study was conducted on 46 Polish KS subjects (41 males, 5 females; average age: 29 years old). The studied KS patients were screened for defects in a 38-gene panel with next-generation sequencing (NGS) technology. The analysis revealed 27 pathogenic and likely pathogenic (P/LP) variants, and 21 variants of uncertain significance (VUS). The P/LP variants were detected in 20 patients (43.5%). The prevalence of oligogenic P/LP defects in selected genes among KS patients was 26% (12/46), whereas the co-occurrence of other variants was detected in 43% (20 probands). The examined KS patients showed substantial genotypic and phenotypic variability. A marked difference in non-reproductive phenotypes, involving defects in genes responsible for GnRH neuron development/migration and genes contributing to pituitary development and signaling, was observed. A comprehensive gene panel for IHH testing enabled the detection of clinically relevant variants in the majority of KS patients, which makes targeted NGS an effective molecular tool. The significance of oligogenicity and the high incidence of alterations in selected genes should be further elucidated.

Idiopathic hypogonadotropic hypogonadism: a rare cause of primary amenorrhoea in adolescence-a review and update on diagnosis, management and advances in genetic understanding

Idiopathic hypogonadotropic hypogonadism (IHH) refers to a family of genetic disorders that affect the production and/or action of gonadotropic-releasing hormone, resulting in reduced serum levels of sex steroids. This condition has a prevalence of 1-10 cases/100 000 births and is characterised by the absence of spontaneous pubertal development. In women, the condition is characterised by the onset of normal adrenarche, with the absence of thelarche and menarche. Pubertal induction for breast development and uterine growth with oestradiol, and sequential maintenance of a normal menstrual cycle and adequate oestrogen for bone health, with an oestrogen and progesterone, is considered first-line treatment. Pregnancy can be achieved in patients who have received and responded to treatment with ovulation induction with exogenous gonadotrophins. Advances in genetic testing have led to increased research and understanding of the underlying genetics of IHH with gene mutations described in up to 50% of all IHH cases.

Genetics of hypogonadotropic hypogonadism

Male congenital hypogonadotropic hypogonadism (CHH) is a heterogenous group of genetic disorders that cause impairment in the production or action of gonadotropin releasing hormone (GnRH). These defects result in dysfunction of the hypothalamic-pituitary-gonadal hormone axis, leading to low testosterone levels and impaired fertility. Genetic testing techniques have expanded our knowledge of the underlying mechanisms contributing to CHH including over 30 genes to date implicated in the development of CHH. In some cases, non-reproductive signs or symptoms can give clues as to the putative genetic etiology, but many cases remain undiagnosed with less than 50% identified with a specific gene defect. This leads to many patients labelled as “idiopathic hypogonadotropic hypogonadism”. Medical and family history as well as physical exam and laboratory features can aid in the identification of hypogonadotropic hypogonadism (HH) that is associated with specific medical syndromes or associated with other pituitary hormonal deficiencies. Genetic testing strategies are moving away from the classic practice of testing for only a few of the most commonly affected genes and instead utilizing next generation sequencing techniques that allow testing of numerous potential gene targets simultaneously. Treatment of CHH is dependent on the individual’s desire to preserve fertility and commonly include human chorionic gonadotropin (hCG) and recombinant follicle stimulating hormone (rFSH) to stimulate testosterone production and spermatogenesis. In situations where fertility is not desired, testosterone replacement therapies are widely offered in order to maintain virilization and sexual function.

Neurobiology of puberty and its disorders

Puberty, which in humans is considered to include both gonadarche and adrenarche, is the period of becoming capable of reproducing sexually and is recognized by maturation of the gonads and development of secondary sex characteristics. Gonadarche referring to growth and maturation of the gonads is fundamental to puberty since it encompasses increased gonadal steroid secretion and initiation of gametogenesis resulting from enhanced pituitary gonadotropin secretion, triggered in turn by robust pulsatile GnRH release from the hypothalamus. This chapter reviews the development of GnRH pulsatility from before birth until the onset of puberty. In humans, GnRH pulse generation is restrained during childhood and juvenile development. This prepubertal hiatus in hypothalamic activity is considered to result from a neurobiological brake imposed upon the GnRH pulse generator resident in the infundibular nucleus. Reactivation of the GnRH pulse generator initiates pubertal development. Current understanding of the genetics and physiology of the brake will be discussed, as will hypotheses proposed to account for timing the resurgence in pulsatile GnRH and initiation of puberty. The chapter ends with a discussion of disorders associated with precocious or delayed puberty with a focus on those with etiologies attributed to aberrant GnRH neuron anatomy or function. A pediatric approach to patients with pubertal disorders is provided and contemporary treatments for both precocious and delayed puberty outlined.

Kallmann syndrome and idiopathic hypogonadotropic hypogonadism: The role of semaphorin signaling on GnRH neurons

Idiopathic hypogonadotropic hypogonadism and Kallmann syndrome are rare genetic disorders characterized by isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) and delayed or absent puberty. Defective GnRH neuron migration during development or secretion of mature GnRH neurons secondary to molecular defects in several key developmental and neuroendocrine pathways are thought to be the primary causes of these disorders. Recent studies have highlighted the importance of semaphorins and their receptors in this system, by showing that these molecules play distinct roles during the development and plasticity of these neurons. Accordingly, mutations in the semaphoring-signaling pathway genes have been found in patients affected by IGD, underlying the importance of semaphorin-mediated signaling pathways in the neuroendocrine axis that control reproduction.

Exploring the Genetic Diversity of Isolated Hypogonadotropic Hypogonadism and Its Phenotypic Spectrum: A Case Series

Background:

Isolated hypogonadotropic hypogonadism (IHH) is a rare disorder being classified as Kallmann syndrome (KS). The present study was conducted to study the genotype and relative proportion of different genetic mutations in IHH and to assess its correlation with phenotype.

Methods:

Eleven consecutive subjects presenting to the Department of Endocrinology were retrospectively analyzed during May 2017 to December 2018 with IHH. Phenotypic features and hormonal studies were analyzed along with clinical exome by targeted gene sequencing (Next generation sequencing). Thirty-nine relevant genes were tested in the analysis.

Results:

Of the 11 patients studied, five had KS and six had nIHH. At diagnosis, mean chronological age was 25 years. There were associated anomalies in KS group including bimanual synkinesia (n=2), unilateral renal agenesis (n=1) and submucosal cleft palate (n=1). Absence or hypoplasia of the olfactory bulb/sulci was found in 4/5 patients with KS. Genetic mutations in KAL1, CHD7, FGFR1, GNRHR, PROKR2, HS6ST1 genes were found in nine of the eleven subjects. Of the five subjects with KS, two had mutations in KAL1 gene. Two siblings who had bimanual synkinesia had CHD7 mutation. The genotype of nIHH subjects (n=6) was more heterogeneous.

Conclusion:

This study analyzed the clinical, endocrinological, and genetic features in IHH patients. Detectable genetic mutations were seen in a large proportion of cases. A considerable heterogeneity was seen in the genotype with new variants detected. A definite correlation of phenotype-genotype was not possible, and significant overlap was seen between CHD7 and KAl1, and FGFR1 phenotypes.

Posttranslational Modification Defects in Fibroblast Growth Factor Receptor 1 as a Reason for Normosmic Isolated Hypogonadotropic Hypogonadism

Some mutations in FGFR1 affect the sense of smell while others do not, resulting in Kallmann syndrome (KS) and normosmic isolated hypogonadotropic hypogonadism (nIHH), respectively. The underlying mechanism is still unclear. FGFR1 variants are found in less than 10% of patients with KS and nIHH, and among them, only some have undergone functional analysis. Thus, the correlation between the phenotype and genotype cannot be clearly verified. This study reports a case of nIHH and explores the potential mechanism of the FGFR1 gene in the pathogenesis of nIHH. A preschooler with cryptorchidism, micropenis, strabismus, and hypopsia is described. As he had a normal sense of smell, he was diagnosed with nIHH. A de novo mutation in FGFR1 (c.2008G>A) was detected in the patient along with a novel variant in CEP290 (c.964G>A) inherited from his mother. We present compelling in vitro evidence that this FGFR1 mutation-induced posttranslational modification defect, including defective glycosylation and impaired trans-autophosphorylation, along with the final reduction in expression, could lead to impairment of the receptor and abnormal signaling and eventually result in developmental abnormalities and inhibition of GnRH neuron release. The identification of an additional variant suggests that CEP290 might play a potential role in GnRH development.

An isolated hypogonadotropic hypogonadism male with a novel de novoFGFR1 mutation fathered a normal son evidenced by prenatal genetic diagnosis

Isolated hypogonadotropic hypogonadism (IHH) is a rare but treatable form of male infertility caused by congenital defect in gonadotropin-releasing hormone (GnRH) secretion or action. We report a Chinese IHH male with a novel FGFR1 mutation who successfully fathered a normal son. Targeted next-generation sequencing, bioinformatics analysis and Sanger sequencing were performed by using the DNA extracted from the pedigree. The patient was treated with gonadotropin and was able to impregnant his wife during the treatment. Amniocentesis was performed at the 18 weeks of gestation. A novel de novo pathogenic missense variant (c.980A>G, p.Asn327Ser) in exon 8 in FGFR1 gene (NM_001174067.1) was identified in the patient but not in his normal parents. This variant was also absent in the DNA obtained from the amniocentesis sample. His son has normal growth and development at the age of 2 years. This is the first case of prenatal genetic diagnosis based on the genetic testing of the IHH father by combining targeted next-generation and Sanger sequencing in IHH family. We extended the mutation spectrum of FGFR1 in IHH patients. Prenatal genetic diagnosis based on the results of genetic testing of the IHH patients may be helpful in the genetic counselling for the IHH families.

A novel SOX10 variant in a Japanese girl with Waardenburg syndrome type 4C and Kallmann syndrome

We report the first case of Waardenburg syndrome type 4C and Kallmann syndrome in the same person. The patient, a Japanese girl, presented with bilateral iris depigmentation, bilateral sensorineural hearing loss, Hirschsprung disease, hypogonadotropic hypogonadism, and anosmia. We identified a novel SOX10 variant, c.124delC, p.Leu42Cysfs*67.

Combined in vitro and in silico analyses of FGFR1 variants: genotype-phenotype study in idiopathic hypogonadotropic hypogonadism

Fibroblast growth factor receptor 1 (FGFR1) is an idiopathic hypogonadotropic hypogonadism (IHH)-associated gene, mutated in approximately 10% of the patients with this condition. Through targeted gene sequencing of 153 males with IHH and 100 healthy controls, we identified 10 mutations in FGFR1 from IHH patients with a frequency of 5.9% in the Chinese population of central China. These included nine missense mutations(NM_023110.2, p.Gly687Arg, p.Ala608Asp, p.Gly348Glu, p.Asn296Ser, p.Gly226Asp, p.Arg209Cys, p.Gly97Arg, p.Val71Met, p.Gly70Arg) and a splicing mutation c.1430 + 1G > T. in vitro and in silico analyses of FGFR1 variants were conducted to study the impact of the identified mutations. Our findings indicated that the splicing mutation dramatically affected premRNA processing, causing exon 10 and 6 nucleotides in the 3' end of exon 9 to be completely skipped. Two variants (p.Gly687Arg and p.Ala608Asp) markedly impaired tyrosine kinase activity, while the other variants had limited impact on the mitogen-activated protein kinase (MAPK) signaling pathway. However, the functional impairment of the mutant receptors was not always consistent with the phenotypes, indicating that FGFR1 mutations might cause IHH in conjunction with other mutant genes. In this study, we expanded the knowledge on the mutation spectrum of FGFR1 in IHH patients and explored the genotype-phenotype relationship.

Functional Characteristics of Novel FGFR1 Mutations in Patients with Isolated Gonadotropin-Releasing Hormone Deficiency

BACKGROUND

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) has a wide phenotypic spectrum including Kallmann syndrome (KS) and normosmic idiopathic hypogonadotropic hypogonadism (nIHH). FGFR1 mutations have been identified in 3-10% of patients with KS or nIHH. This study was performed to investigate clinical phenotypes and functional characteristics of FGFR1 mutations in patients with IGD.

METHODS

This study included 8 patients (from 7 families) with FGFR1 mutations identified by targeted gene panel sequencing or whole exome sequencing (WES). The impact of the identified mutations on FGFR1 function was assessed using in vitro studies.

RESULTS

Seven heterozygous mutations in FGFR1 were identified in 8 patients from 7 independent families. The patients exhibited a wide spectrum of pubertal development, including anosmia in a prepubertal boy (n=1), delayed puberty (n=2), nIHH (n=3), and KS (n=2). Four of the mutations were classified as likely pathogenic, and the other three were variants of uncertain significance. FGF8-FGFR1 signaling activities for the novel FGFR1 variants (p.Y339H, p.S681I, and p.N185Kfs*16) were reduced by in vitro functional assay, indicating loss-of-function mutations.

CONCLUSIONS

This study identified seven rare sequence variants in FGFR1 in patients with KS and nIHH. Probands with an FGFR1 mutations displayed a wide phenotypic spectrum ranging from KS to anosmia. A prepubertal male with anosmia should be followed up to assess pubertal development because they can manifest hypogonadotropic hypogonadism after puberty. These results expand the phenotypic spectrum of FGFR1 mutations and suggest a broader biologic role of FGFR1 in reproduction.

Prevalence and associated phenotypes of DUSP6, IL17RD and SPRY4 variants in a large Chinese cohort with isolated hypogonadotropic hypogonadism

BACKGROUND

FGF8-FGFR1 signalling is involved in multiple biological processes, while impairment of this signalling is one of the main reasons for isolated hypogonadotropic hypogonadism (IHH). Recently, several negative modulators of FGF8-FGFR1 signalling were also found to be involved in IHH, including DUSP6, IL17RD, SPRY2 and SPRY4. The aim of this study was to investigate the genotypic and phenotypic spectra of these genes in a large cohort of Chinese patients with IHH.

METHODS

A total of 196 patients with IHH were enrolled in this study. Whole-exome sequencing was performed to identify variants, which was verified by PCR and Sanger sequencing.

RESULTS

Four heterozygous DUSP6 variants (p.S157I, p.R83Q, p.P188L and p.N355I) were found in six patients. Cryptorchidism, dental agenesis, syndactyly and blue colour blindness were commonly observed in patients with DUSP6 mutations. Six heterozygous IL17RD variants (p.P191L, p.G35V, p.S671L, p.A221T, p.I329M and p.I329V) were found in seven patients. Segregation analysis indicated that 100% (5/5) of probands inherited the IL17RD variants from their unaffected parents, and oligogenicity was found in 4/7 patients. One rare SPRY4 variant (p.T68S) was found in a female patient with Kallmann syndrome who also carried a PLXNA1 mutation.

CONCLUSION

Our study greatly enriched the genotypic and phenotypic spectra of DUSP6, IL17RD and SPRY4 in IHH. Mutations in DUSP6 alone seem sufficient to cause IHH in an autosomal dominant manner, whereas IL17RD or SPRY4 mutations may cause IHH phenotypes in synergy with variants in other IHH-associated genes.

Phenotypic Spectrum of Idiopathic Hypogonadotropic Hypogonadism Patients With CHD7 Variants From a Large Chinese Cohort

PURPOSE

Idiopathic hypogonadotropic hypogonadism (IHH) and CHARGE (C, coloboma; H, heart abnormalities; A, choanal atresia, R, retardation of growth and/or development; G, gonadal defects; E, ear deformities and deafness) syndrome are 2 distinct developmental disorders sharing features of hypogonadism and/or impaired olfaction. CHD7 variants contribute to >60% CHARGE syndrome and ~10% IHH patients. A variety of extended CHARGE-like features are frequently reported in CHARGE patients harboring CHD7 variants. In this study, we aimed to systematically analyze the diagnostic CHARGE features and the extended CHARGE-like features in patients with IHH with CHD7 variants.

METHODS

Rare sequencing variants (RSVs) in CHD7 were identified through exome sequencing in 177 IHH probands. Detailed phenotyping was performed in the IHH patients harboring CHD7 variants and their available family members.

RESULTS

CHD7 RSVs were identified in 10.2% (18/177) of the IHH probands. Two diagnostic CHARGE features, hearing loss and ear deformities, were significantly enriched in patients with CHD7 variants. Furthermore, CHD7 variants were significantly associated with a panel of extended CHARGE-like phenotypes, including mild ocular defects, dyspepsia/gastroesophageal reflux disease and skeletal defects. We also developed a predictive model for prioritizing CHD7 genetic testing in IHH patients.

CONCLUSION

CHD7 variants rarely cause isolated IHH. Surveillance of symptoms in CHARGE syndrome-affected organs will facilitate the proper treatment for these patients. Certain clinical features can be useful for prioritizing CHD7 genetic screening.

Molecular genetic diagnostics of hypogonadotropic hypogonadism: from panel design towards result interpretation in clinical practice

Congenital hypogonadotropic hypogonadism (CHH) is a clinically and genetically heterogeneous congenital disease. Symptoms cover a wide spectrum from mild forms to complex phenotypes due to gonadotropin-releasing hormone (GnRH) deficiency. To date, more than 40 genes have been identified as pathogenic cause of CHH. These genes could be grouped into two major categories: genes controlling development and GnRH neuron migration and genes being responsible for neuroendocrine regulation and GnRH neuron function. High-throughput, next-generation sequencing (NGS) allows to analyze numerous gene sequences at the same time. Nowadays, whole exome or whole genome datasets could be investigated in clinical genetic diagnostics due to their favorable cost-benefit. The increasing genetic data generated by NGS reveal novel candidate genes and gene variants with unknown significance (VUSs). To provide clinically valuable genetic results, complex clinical and bioinformatics work are needed. The multifaceted genetics of CHH, the variable mode of inheritance, the incomplete penetrance, variable expressivity and oligogenic characteristics further complicate the interpretation of the genetic variants detected. The objective of this work, apart from reviewing the currently known genes associated with CHH, was to summarize the advantages and disadvantages of the NGS-based platforms and through the authors' own practice to guide through the whole workflow starting from gene panel design, performance analysis and result interpretation. Based on our results, a genetic diagnosis was clearly identified in 21% of cases tested (8/38).

Genetics of congenital hypogonadotropic hypogonadism: peculiarities and phenotype of an oligogenic disease

A genetic basis of congenital isolated hypogonadotropic hypogonadism (CHH) can be defined in almost 50% of cases, albeit not necessarily the complete genetic basis. Next-generation sequencing (NGS) techniques have led to the discovery of a great number of loci, each of which has illuminated our understanding of human gonadotropin-releasing hormone (GnRH) neurons, either in respect of their embryonic development or their neuroendocrine regulation as the "pilot light" of human reproduction. However, because each new gene linked to CHH only seems to underpin another small percentage of total patient cases, we are still far from achieving a comprehensive understanding of the genetic basis of CHH. Patients have generally not benefited from advances in genetics in respect of novel therapies. In most cases, even genetic counselling is limited by issues of apparent variability in expressivity and penetrance that are likely underpinned by oligogenicity in respect of known and unknown genes. Robust genotype-phenotype relationships can generally only be established for individuals who are homozygous, hemizygous or compound heterozygotes for the same gene of variant alleles that are predicted to be deleterious. While certain genes are purely associated with normosmic CHH (nCHH) some purely with the anosmic form (Kallmann syndrome-KS), other genes can be associated with both nCHH and KS-sometimes even within the same kindred. Even though the anticipated genetic overlap between CHH and constitutional delay in growth and puberty (CDGP) has not materialised, previously unanticipated genetic relationships have emerged, comprising conditions of combined (or multiple) pituitary hormone deficiency (CPHD), hypothalamic amenorrhea (HA) and CHARGE syndrome. In this review, we report the current evidence in relation to phenotype and genetic peculiarities regarding 60 genes whose loss-of-function variants can disrupt the central regulation of reproduction at many levels: impairing GnRH neurons migration, differentiation or activation; disrupting neuroendocrine control of GnRH secretion; preventing GnRH neuron migration or function and/or gonadotropin secretion and action.

Correlations Among Genotype and Outcome in Chinese Male Patients With Congenital Hypogonadotropic Hypogonadism Under HCG Treatment

BACKGROUND

Congenital hypogonadotropic hypogonadism (CHH) is a genetically heterogeneous disorder characterized by absent or incomplete puberty and infertility, and heterogeneous responses are often observed during treatment.

AIM

To investigate the role of CHH-associated variants in patients with CHH with poor responses to human chorionic gonadotropin (hCG).

METHODS

This retrospective study investigated 110 Chinese male patients with CHH undergoing genetic analysis and hCG treatment. CHH-associated rare sequence variants (RSVs) were identified by using a tailored next-generation sequencing panel and were interpreted in accordance with the American College of Medical Genetics and Genomics criteria. Clinical characteristics were recorded, and Kyoto Encyclopedia of Genes and Genomes analysis was conducted to assess pathways enriched in protein networks implicated in poor responses.

OUTCOMES

The outcomes include testicular volume, serum hormonal profiles, parameters of semen analysis, pathogenicity classification, and pathway enrichment.

RESULTS

Among the 110 patients, 94.55% achieved normal serum testosterone and 54.55% achieved seminal spermatozoa appearance (SSA). PLXNB1, ROBO3, LHB, NRP2, CHD7, and PLXNA1 RSVs were identified in patients who had an abnormal serum testosterone level during treatment. In spermatogenesis, the number of CHH-associated RSVs was not significantly strongly associated with delayed SSA. After pathogenicity classification, pathogenic/likely pathogenic (P/LP) RSVs were identified in 30% (33/110) of patients. Patients with P/LP RSVs showed delayed SSA compared with noncarriers, and P/LP PROKR2 RSVs showed the strongest association (48, 95% CI: 34.1-61.9 months, P = .043). Enriched pathways implicated in delayed SSA included neuroactive ligand-receptor interaction; Rap1, MAPK, PI3K-Akt signaling; and regulation of actin cytoskeleton.

CLINICAL IMPLICATIONS

Male patients with CHH harboring P/LP PROKR2 RSVs should be aware of a high probability of poor responses to hCG; If these patients desire fertility, it might be better to recommend hCG/human menopausal gonadotropin, hCG/recombinant follicle-stimulating hormone, or pulsatile GnRH administration before treatments start or as early as possible.

STRENGTHS & LIMITATIONS

Strengths are the standardized regimen and extensive follow-up (median time of 40 months). However, included patients in the study voluntarily chose hCG treatment because of the burden of drug cost and/or little fertility desire. Therefore, human menopausal gonadotropin or follicle-stimulating hormone was not added to this cohort. Our observed correlations should be further verified in patients with CHH undergoing other treatments.

CONCLUSION

Among all P/LP RSVs, P/LP PROKR2 RSVs might correlate with poor responses in CHH under hCG treatment; our study supports the pathogenicity assessment of American College of Medical Genetics and Genomics criteria in genetic counseling, to improve management of patients with CHH. Chen Y, Sun T, Niu Y, et al. Correlations AmongGenotype and Outcome in Chinese Male Patients WithCongenital Hypogonadotropic Hypogonadism Under HCG Treatment. J Sex Med 2020;17:645-657.

Genetic Evaluation of Patients With Delayed Puberty and Congenital Hypogonadotropic Hypogonadism: Is it Worthy of Consideration?

Delayed puberty is a common reason of pediatric endocrinological consultation. It is often a self-limited (or constitutional) condition with a strong familial basis. The type of inheritance is variable but most commonly autosomal dominant. Despite this strong genetic determinant, mutations in genes implicated in the regulation of hypothalamic-pituitary-gonadal axis have rarely been identified in cases of self-limited delayed puberty and often in relatives of patients with congenital hypogonadotropic hypogonadism (i.e., FGFR1 and GNRHR genes). However, recently, next-generation sequencing analysis has led to the discovery of new genes (i.e., IGSF10, HS6ST1, FTO, and EAP1) that are implicated in determining isolated self-limited delayed puberty in some families. Despite the heterogeneity of genetic defects resulting in delayed puberty, genetic testing may become a useful diagnostic tool for the correct classification and management of patients with delayed puberty. This article will discuss the benefits and the limitations of genetic testing execution in cases of delayed puberty.

GnRH Deficient Patients With Congenital Hypogonadotropic Hypogonadism: Novel Genetic Findings in ANOS1, RNF216, WDR11, FGFR1, CHD7, and POLR3A Genes in a Case Series and Review of the Literature

Background: Congenital hypogonadotropic hypogonadism (CHH) is a rare genetic disease caused by Gonadotropin-Releasing Hormone (GnRH) deficiency. So far a limited number of variants in several genes have been associated with the pathogenesis of the disease. In this original research and review manuscript the retrospective analysis of known variants in ANOS1 (KAL1), RNF216, WDR11, FGFR1, CHD7, and POLR3A genes is described, along with novel variants identified in patients with CHH by the present study. Methods: Seven GnRH deficient unrelated Cypriot patients underwent whole exome sequencing (WES) by Next Generation Sequencing (NGS). The identified novel variants were initially examined by in silico computational algorithms and structural analysis of their predicted pathogenicity at the protein level was confirmed. Results: In four non-related GnRH males, a novel X-linked pathogenic variant in ANOS1 gene, two novel autosomal dominant (AD) probably pathogenic variants in WDR11 and FGFR1 genes and one rare AD probably pathogenic variant in CHD7 gene were identified. A rare autosomal recessive (AR) variant in the SRA1 gene was identified in homozygosity in a female patient, whilst two other male patients were also, respectively, found to carry novel or previously reported rare pathogenic variants in more than one genes; FGFR1/POLR3A and SRA1/RNF216. Conclusion: This report embraces the description of novel and previously reported rare pathogenic variants in a series of genes known to be implicated in the biological development of CHH. Notably, patients with CHH can harbor pathogenic rare variants in more than one gene which raises the hypothesis of locus-locus interactions providing evidence for digenic inheritance. The identification of such aberrations by NGS can be very informative for the management and future planning of these patients.

Three Siblings with Idiopathic Hypogonadotropic Hypogonadism in a Nonconsanguineous Family: A Novel KISS1R/GPR54 Loss-of-Function Mutation

Idiopathic hypogonadotropic hypogonadism (IHH) is a rare disease caused by defects in the secretion of gonadotropin releasing hormone (GnRH) or the action of GnRH on the pituitary gonadotrophes. KISS1R is one of the genes which, when mutated, cause IHH and mutations of this gene are responsible for about 2-5% of patients with normosmic IHH (NIHH). In this report, we present three siblings with NIHH due to a compound heterozygous KISS1R mutation. Genetic studies were carried out in the 14 year old index case with IHH and three siblings, two of whom were prepubertal. Genomic DNA was extracted from peripheral leukocytes and KISS1R gene was sequenced by using standard polymerase chain reaction amplification procedures. In molecular analysis of the index case, a compound heterozygous mutation was determined in KISS1R gene c.969C>A (p.Y323X) (known pathogenic) and c.170T>C (p.L57P) (novel). Mutation c.170T>C (p.L57P) was inherited from the mother while c.969C>A (p.Y323X) was inherited from the father. The same genotype was also found in two of the three siblings. A compound heterozygous mutation of the KISS1 gene, including one novel mutation, was found to cause NIHH and also incomplete puberty in a non-consanguineous family.

Live birth in male de novo Kallmann syndrome after cross-generational genetic sequencing

PURPOSE

To present the first case proposing the use of preimplantation genetic testing for monogeneic disorders for Kallmann syndrome, providing comprehensive care in the genomic era of precision medicine.

METHODS

Gonadotropin therapy was used for spermatogenesis, followed by in vitro fertilization by intracytoplasmic sperm injection and embryo transfer. Cross-generational targeted next-generation sequencing was then done for genes known to cause Kallmann syndrome.

RESULTS

A heterozygous mutation at codon 102 of the FGFR1 gene was found in the patient, but the father was found to have the same mutation yet is unaffected by Kallmann syndrome. Since no causative mutation was found, a de novo or sporadic mutation was suspected as the cause of Kallmann syndrome in this case.

CONCLUSIONS

Comprehensive care must be available for male Kallmann syndrome patients, as treatment should not stop at spermatogenesis, but continue with genetic counseling due to possible inheritance.

Genotypic and phenotypic spectra of FGFR1, FGF8, and FGF17 mutations in a Chinese cohort with idiopathic hypogonadotropic hypogonadism

OBJECTIVE

To analyze the prevalence of FGFR1, FGF8, and FGF17 mutations in a Chinese cohort with idiopathic hypogonadotropic hypogonadism (IHH) and to characterize the clinical presentations and therapeutic outcomes of IHH patients with FGFR1, FGF8, and FGF17 mutations.

DESIGN

Retrospective cohort.

SETTING

University hospital.

PATIENT(S)

A total of 145 IHH probands (125 men and 20 women) were recruited for this study.

INTERVENTIONS(S)

Hormone assays.

MAIN OUTCOME MEASURE(S)

Whole-exome sequencing, polymerase chain reaction-Sanger sequencing, in silico functional prediction.

RESULT(S)

Six novel mutations (p.154_158del, p.E496Rfs*12, p.W190X, p.S134D, p.W10X, and c.1552 + 3insT) in FGFR1, two novel mutations (p.E176K and p.R184C) in FGF8, three novel mutations (p.48_52del, p.P120L, and p.K191R) in FGF17, and five reported mutations (p.W289X, p.G237S, p.V102I, p.R250Q, and p.T340M) in FGFR1 were identified in 18 IHH patients. The functional consequences of all mutations were analyzed in silico. In addition to hypogonadotropic hypogonadism, 44.4% (8/18) patients exhibited other clinical deformities, including dental agenesis (3/18, 16.7%), hearing loss (3/18, 16.7%), and hand malformation (2/18, 11.1%). hCG/hMG therapy was effective in promoting sexual development in IHH patients with FGFR1, FGF8, and FGF17 mutations.

CONCLUSION(S)

We extended the mutational spectrum of FGFR1, FGF8, and FGF17 in IHH patients. The prevalence of FGFR1, FGF8, and FGF17 mutations in IHH was 12.4%. hCG/hMG therapy was effective to acquire fertility for patients with FGFR1, FGF8, and FGF17 mutations but has a risk of transmitting the mutations and IHH to the next generation.

Growth in CHARGE syndrome: optimizing care with a multidisciplinary approach

CHARGE (Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital hypoplasia, Ear anomalies including hearing loss) syndrome is a rare syndrome with an incidence of approximately 1:15,000 newborns. It is caused by pathogenic variants in the CHD7 gene and clinically characterized by a wide range of anomalies with variable expression. Growth retardation affects 60-72% of children with CHARGE syndrome, making it one of the most prominent medical issues in the syndrome. Growth retardation in CHARGE syndrome is thought to be multifactorial and can be influenced by almost all co-morbidities, requiring a multidisciplinary approach to the different medical problems. In this systematic review, we describe what is currently known about growth in CHARGE syndrome and how it is influenced by commonly seen clinical problems including feeding difficulties, hypogonadotropic hypogonadism and growth hormone deficiency. Furthermore, we provide recommendations for a multidisciplinary approach.

Nasal Placode Development, GnRH Neuronal Migration and Kallmann Syndrome

The development of Gonadotropin releasing hormone-1 (GnRH) neurons is important for a functional reproduction system in vertebrates. Disruption of GnRH results in hypogonadism and if accompanied by anosmia is termed Kallmann Syndrome (KS). From their origin in the nasal placode, GnRH neurons migrate along the olfactory-derived vomeronasal axons to the nasal forebrain junction and then turn caudally into the developing forebrain. Although research on the origin of GnRH neurons, their migration and genes associated with KS has identified multiple factors that influence development of this system, several aspects still remain unclear. This review discusses development of the olfactory system, factors that regulate GnRH neuron formation and development of the olfactory system, migration of the GnRH neurons from the nose into the brain, and mutations in humans with KS that result from disruption of normal GnRH/olfactory systems development.