Normosmic Isolated Hypogonadotropic Hypogonadism Research Articles

Reproductive Phenotypes and Genotypes in Men With IHH.

Isolated hypogonadotropic hypogonadism (IHH) is phenotypically and genetically heterogeneous. This work aimed to determine the correlation between genotypic severity with pubertal and neuroendocrine phenotypes in IHH men. 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). 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. 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.

Prevalence and Phenotypic Effects of Copy Number Variants in Isolated Hypogonadotropic Hypogonadism.

The genetic architecture of isolated hypogonadotropic hypogonadism (IHH) has not been completely defined. To determine the role of copy number variants (CNVs) in IHH pathogenicity and define their phenotypic spectrum. Exome sequencing (ES) data in IHH probands (n = 1394) (Kallmann syndrome [IHH with anosmia; KS], n = 706; normosmic IHH [nIHH], n = 688) and family members (n = 1092) at the Reproductive Endocrine Unit and the Center for Genomic Medicine of Massachusetts General Hospital were analyzed for CNVs and single nucleotide variants (SNVs)/indels in 62 known IHH genes. IHH subjects without SNVs/indels in known genes were considered "unsolved." Phenotypes associated with CNVs were evaluated through review of patient medical records. A total of 29 CNVs in 13 genes were detected (overall IHH cohort prevalence: ~2%). Almost all (28/29) CNVs occurred in unsolved IHH cases. While some genes (eg, ANOS1 and FGFR1) frequently harbor both CNVs and SNVs/indels, the mutational spectrum of others (eg, CHD7) was restricted to SNVs/indels. Syndromic phenotypes were seen in 83% and 63% of IHH subjects with multigenic and single gene CNVs, respectively. CNVs in known genes contribute to ~2% of IHH pathogenesis. Predictably, multigenic contiguous CNVs resulted in syndromic phenotypes. Syndromic phenotypes resulting from single gene CNVs validate pleiotropy of some IHH genes. Genome sequencing approaches are now needed to identify novel genes and/or other elusive variants (eg, noncoding/complex structural variants) that may explain the remaining missing etiology of IHH.

Clinical and molecular features of idiopathic hypogonadotropic hypogonadism in Taiwan: A single center experience

Idiopathic (isolated) hypogonadotropic hypogonadism (IHH) is a rare disease that can be classified as Kallmann syndrome (KS) or normosmic IHH (nIHH). This study investigated the phenotype and genotype of IHH in Taiwanese patients. Twenty-six unrelated IHH patients were included in this study and their clinical, hormonal, and radiological findings were analyzed retrospectively. Whole exome sequencing (WES) was performed to identify the etiology. The 26 patients (M:F=19:7) were divided into a KS group (n=11) and a nIHH group (n=15). The diagnosis was earlier in boys than in girls. Fifteen patients were found to have pathogenic/likely pathogenic (P/LP) variants of IHH-associated genes, and the mutation detection rate was 58%. CHD7, FGFR1, and ANOS1 were the most common genetic etiologies identified in this group. Two patients with nIHH were found to have de novo SOX11 mutations and Coffin-Siris syndrome features. After treatment, the height outcomes and secondary sexual characteristics were significantly improved. There were no obvious differences between the genetically resolved (GR), variants of uncertain significance (VUS) and genetically unresolved groups (GUR). Whole exome sequencing is useful in patients with IHH, and we identified the SOX11 gene as a causal factor in this study. We described the clinical, hormonal, and molecular characteristics, and the treatment outcomes, of Taiwanese patients with IHH, which should aid therapeutic planning and further research.

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.

Functional analysis of SEMA3A variants identified in Chinese patients with isolated hypogonadotropic hypogonadism.

Isolated hypogonadotropic hypogonadism (IHH) is a rare disorder characterized by impaired sexual development and infertility, caused by the deficiency of hypothalamic gonadotropin-releasing hormone neurons. IHH is named Kallmann's syndrome (KS) or normosmic IHH (nIHH) when associated with a defective or normal sense of smell. Variants in SEMA3A have been recently identified in patients with KS. In this study, we screened SEMA3A variants in a cohort of Chinese patients with IHH by whole exome sequencing. Three novel heterozygous SEMA3A variants (R197Q, R617Q and V458I) were identified in two nIHH and one KS patients, respectively. Functional studies indicated that R197Q and R617Q variants were ineffective in activating the phosphorylation of FAK (focal adhesion kinase) in GN11 cells, despite normal production and secretion in HEK293T cells. The V458I SEMA3A had defect in secretion as it was not detected in the conditioned medium from HEK293T cells. Compared with wild type SEMA3A protein, all three SEMA3A mutant proteins were ineffective in inducing the migration of GN11 cells. Our study further showed the contribution of SEMA3A loss-of-function variants to the pathogenesis of IHH.

Spectrum of phenotype and genotype of congenital isolated hypogonadotropic hypogonadism in Asian Indians.

Congenital isolated hypogonadotropic hypogonadism (IHH) is caused due to defect in GnRH neuronal development, migration and action. Although genetic aetiology of IHH is increasingly being studied, Asian Indian data on phenotypic spectrum and genetic basis are scarce. To investigate the phenotypic and genotypic spectrum of IHH in Asian Indian subjects. A cohort of 135 IHH probands were characterized phenotypically for reproductive and nonreproductive features and screened for rare sequence variations (RSVs) in five genes KAL1, FGFR1, FGF8, GNRHR and KISS1R. Of 135 probands [56 normosmic IHH (nIHH) and 79 Kallmann syndrome (KS)], 20 were familial cases. KS group had more male dominance (M:F ratio of 8:1) as compared to nIHH group (M:F ratio of 1·5:1). Complete absence of puberty was more prevalent in KS probands (81% in KS vs 46% in nIHH). The prevalence of MRI abnormalities was more in anosmic group (92·8%) as compared to hyposmic (37·5%) and normosmic groups (15·4%). No particular nonreproductive phenotypic predominance was seen in any group. Genotyping revealed rare sequence variation (RSV) detection rate of 15·5% in five genes studied: (KAL1 - 4·4%, FGFR1 - 4·4%, GNRHR - 6·7%, oligogenicity - 1·5%). Prevalence of RSV was more common in familial cases (35%) as compared to sporadic (12·2%). GNRHR RSV p.C279Y (not reported in patients of ethnicities other than south Asians) was recurring in four unrelated patients. In our cohort, 60% were KS with majority of males and a severe reproductive phenotype as against nIHH. Contribution of the genetic burden for the five genes studied was 15·5%. RSV p.C279Y in GNRHR may have a founder effect originating from south Asia. This study provides a model for molecular and phenotypic representation of Asian Indian subjects with IHH.

AB158. A total of 213 cases with male isolated gonadotropin-releasing hormone deficiency: clinical feature analysis and gene mutation study in some cases.

ObjectiveIsolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) is a rare clinical condition with a broad spectrum of human reproductive disorders which varies from congenital isolated hypogonadotropic hypogonadism (IHH) to constitutional delay of puberty (CDP) and adult-onset isolated hypogonadotropic hypogonadism (AHH) in male. In the presence of anosmia or hyposmia, IHH is defined as Kallmann syndrome (KS), whereas in the presence of a normal sense of smell, it is termed normosmic IHH (nIHH). In this study, we described the clinical features of 213 Chinese IGD males, and performed genetic study in some of these cases, and analyzed their genotype phenotype correlations.MethodsWe collected the male isolated GnRH deficiency patients in our outpatient and filed their medical and family history. The physical examinations, laboratory and imaging studies were performed. The PCR and agarose gel electrophoresis, whole genome chip and semiconductor target areas sequencing were used to reveal the molecular defects of two KS and ichthyosis brothers. We also used semiconductor target areas sequencing and Sanger sequencing to detect the mutations in 15 IHH causative genes in 4 KS patients with cleft lip/palate (CLP) and 8 IGD patients (including 5 KS patients, one nIHH patients and two AIHH patients) without CLP. Functional prediction and conservation analysis were performed to predict the consequence of the three mutations.ResultsThe reproductive phenotypes in the IHH patients included Gynecomastia (23/210), microphallus (42/210), cryptorchidism (21/210), unilateral testicular agenesis (2/210), scrotum dysplasia (3/210). The non-reproductive phenotypes in our patients contained ichthyosis (3/210), unilateral renal agenesis (2/210), cleft lip (2/210), cleft lip and dental agenesis (1/210), cleft lip and palate combined with dental agenesis and high arched palate (1/210), nystagmus and iris hypoplasia (1/210). These non-reproductive phenotypes only presented in KS patients. The results of karyotype analysis showed that 15 out of the 210 IHH patients (7.1%) had polymorphic chromosomal variants.. The phenotypes of the two Chinese brothers with KS and X-linked ichthyosis were characterised by bilateral cryptorchidism, unilateral renal agenesis in one patient but normal kidney development in another. Genetic study showed that the two affected siblings had the same novel deletion at Xp22.3 including exons 9-14 of KAL1 gene and entire STS gene. We also identified two novel heterozygous missense mutations in FGFR1, (NM_001174066): c.776G>A (p.G259E) and (NM_001174066): c.358C>T (p.R120C), in a 23-yr-old KS male with cleft lip and an 18-year-old KS patient with cleft lip and palate, dental agenesis and high arched palate, respectively. By the way, one heterozygous missense mutation in KISS1R which was reported previously, (NM_032551): c.587C>A (p.P196H), was identified in an 18-yr-old KS male with cleft lip and dental agenesis. All the mutations were not presented in any of the 200 unrelated normal controls. However, we proved the KISS1R c.587C>A mutation was presented in the father and grandfather of the patients.ConclusionsOur study expanded the clinical phenotype and gene mutation spectrum of Chinese IGD patients and has implications for the genetic diagnoses and counseling of IGD.

Role of gonadotropin-releasing hormone receptor mutations in patients with a wide spectrum of pubertal delay

To analyze the GNRHR in patients with normosmic isolated hypogonadotropic hypogonadism (IHH) and constitutional delay of growth and puberty (CDGP). Molecular analysis and invitro experiments correlated with phenotype. Academic medical center. A total of 110 individuals with normosmic IHH (74 male patients) and 50 with CDGP. GNRHR coding region was amplified and sequenced. Novel variants were submitted to invitro analysis. Frequency of mutations and genotype-phenotype correlation were analyzed. Microsatellite markers flanking GNRHR were examined in patients carrying the same mutation to investigate a possible founder effect. Eleven IHH patients (10%) carried biallelic GNRHR mutations. Invitro analysis of novel variants (p.Y283H and p.V134G) demonstrated complete inactivation. The founder effect study revealed that Brazilian patients carrying the p.R139H mutation shared the same haplotype. Phenotypic spectrum in patients with GNRHR mutations varied from complete GnRH deficiency to partial and reversible IHH, with a relatively good genotype-phenotype correlation. One boy with CDGP was heterozygous for the p.Q106R variant, which was not considered to be pathogenic. GNRHR mutations are a frequent cause of congenital normosmic IHH and should be the first candidate gene for genetic screening in this condition, especially in autosomal recessive familial cases. The founder effect study suggested that the p.R139H mutation arises from a common ancestor in the Brazilian population. Finally, mutations in GNRHR do not appear to be involved in the pathogenesis of CDGP.

Mutational analysis of TAC3 and TACR3 genes in patients with idiopathic central pubertal disorders

To investigate the presence of variants in the TAC3 and TACR3 genes, which encode NKB and its receptor (NK3R), respectively, in a large cohort of patients with idiopathic central pubertal disorders. Two hundred and thirty seven patients were studied: 114 with central precocious puberty (CPP), 73 with normosmic isolated hypogonadotropic hypogonadism (IHH), and 50 with constitutional delay of growth and puberty (CDGP). The control group consisted of 150 Brazilian individuals with normal pubertal development. Genomic DNA was extracted from peripheral blood and the entire coding region of both TAC3 and TACR3 genes were amplified and automatically sequenced. We identified one variant (p.A63P) in NKB and four variants, p.G18D, p.L58L (c.172C>T), p.W275* and p.A449S in NK3R, which were absent in the control group. The p.A63P variant was identified in a girl with CPP, and p.A449S in a girl with CDGP. The known p.G18D, p.L58L, and p.W275* variants were identified in three unrelated males with normosmic IHH. Rare variants in the TAC3 and TACR3 genes were identified in patients with central pubertal disorders. Loss-of-function variants of TACR3 were associated with the normosmic IHH phenotype.

Genetics of Isolated Hypogonadotropic Hypogonadism: Role of GnRH Receptor and Other Genes

Hypothalamic gonadotropin releasing hormone (GnRH) is a key player in normal puberty and sexual development and function. Genetic causes of isolated hypogonadotropic hypogonadism (IHH) have been identified during the recent years affecting the synthesis, secretion, or action of GnRH. Developmental defects of GnRH neurons and the olfactory bulb are associated with hyposmia, rarely associated with the clinical phenotypes of synkinesia, cleft palate, ear anomalies, or choanal atresia, and may be due to mutations of KAL1, FGFR1/FGF8, PROKR2/PROK2, or CHD7. Impaired GnRH secretion in normosmic patients with IHH may be caused by deficient hypothalamic GPR54/KISS1, TACR3/TAC3, and leptinR/leptin signalling or mutations within the GNRH1 gene itself. Normosmic IHH is predominantly caused by inactivating mutations in the pituitary GnRH receptor inducing GnRH resistance, while mutations of the β-subunits of LH or FSH are very rare. Inheritance of GnRH deficiency may be oligogenic, explaining variable phenotypes. Future research should identify additional genes involved in the complex network of normal and disturbed puberty and reproduction.

Aspectos clínicos e moleculares do hipogonadismo hipogonadotrófico isolado congênito

Congenital isolated hypogonadotropic hypogonadism (IHH) is characterized by partial or complete lack of pubertal development due to defects in migration, synthesis, secretion or action of gonadotropin-releasing hormone (GnRH). Laboratory diagnosis is based on the presence of low levels of sex steroids, associated with low or inappropriately normal levels of pituitary gonadotropins (LH and FSH). Secretion of other pituitary hormones is normal, as well magnetic resonance imaging of the hypothalamohypophyseal tract, which shows absence of an anatomical defects. When IHH is associated with olfactory abnormalities (anosmia or hyposmia), it characterizes Kallmann syndrome. A growing list of genes is involved in the etiology of IHH, suggesting the heterogeneity and complexity of the genetic bases of this condition. Defects in olfactory and GnRH neuron migration are the etiopathogenic basis of Kallmann syndrome. Mutations in KAL1, FGFR1/FGF8, PROK2/PROKR2, NELF, CHD7, HS6ST1 and WDR11 are associated with defects in neuronal migration, leading to Kallmann syndrome. Notably, defects in FGFR1, FGF8, PROKR2, CHD7 and WDR11 are also associated with IHH, without olfactory abnormalities (normosmic IHH), although in a lower frequency. Mutations in KISS1R, TAC3/TACR3 and GNRH1/GNRHR are described exclusively in patients with normosmic IHH. In this paper, we reviewed the clinical, hormonal and genetic aspects of IHH.

Mutational analysis of the necdin gene in patients with congenital isolated hypogonadotropic hypogonadism

Necdin activates GNRH gene expression and is fundamental for the development, migration, and axonal extension of murine GNRH neurons. In humans, necdin plays a potential role in the hypogonadotropic hypogonadism phenotype in patients with Prader-Willi syndrome. To investigate necdin gene (NDN) variants in patients with isolated hypogonadotropic hypogonadism (IHH). We studied 160 Brazilian patients with IHH, which includes 92 with Kallmann syndrome and 68 with normosmic IHH. Genomic DNA was extracted and the single NDN exon was amplified and sequenced. To measure GNRH transcriptional activity, luciferase reporter plasmids containing GNRH regulatory regions were transiently transfected into GT1-7 cells in the presence and absence of overexpressed wild-type or mutant necdin. A heterozygous variant of necdin, p.V318A, was identified in a 23-year-old male with Kallmann syndrome. The p.V318A was also present in affected aunt and his father and was absent in 100 Brazilian control subjects. Previous FGFR1 gene analysis revealed a missense mutation (p.P366L) in this family. Functional studies revealed a minor difference in the activation of GNRH transcription by mutant protein compared with wild type in that a significant impairment of the necdin protein activity threshold was observed. A rare variant of necdin (p.V318A) was described in a family with Kallmann syndrome associated with a FGFR1 mutation. Familial segregation and in vitro analysis suggested that this non-synonymous variant did not have a direct causative role in the hypogonadism phenotype. NDN mutations are not a frequent cause of congenital IHH.

A Novel Loss-of-Function Mutation in GPR54/KISS1R Leads to Hypogonadotropic Hypogonadism in a Highly Consanguineous Family

Context: The G protein-coupled receptor 54 (GPR54), the kisspeptin receptor, is essential for stimulation of GnRH secretion and induction of puberty. Recently loss-of-function mutations of the GPR54 have been implicated as a cause of isolated hypogonadotropic hypogonadism (IHH). Objective: The objective of the study was to identify the genetic cause of IHH in a consanguineous pedigree and to characterize the phenotypic features from infancy through early adulthood. Design: In six patients with normosmic IHH belonging to two families of Israeli Muslim-Arab origin highly related to one another, DNA was analyzed for mutations in the GNRHR and GPR54 genes, with functional analysis of the mutation found. The five males underwent comprehensive endocrine evaluation and were under longitudinal follow-up; the one female presented in early adulthood. Results: A new homozygous mutation (c.T815C) in GPR54 leading to a phenylalanine substitution by serine (p.F272S) was detected in all patients. Functional analysis showed an almost complete inhibition of kisspeptin-induced GPR54 signaling and a dramatic decrease of the mutated receptor expression at the cell surface. The males exhibited the same clinical features from infancy to adulthood, characterized by cryptorchidism, a relatively short penis, and no spontaneous pubertal development. The female patient presented at 18 yr with impuberism and primary amenorrhea. Repeated stimulation tests demonstrated complete gonadotropin deficiency throughout follow-up. Conclusion: A novel loss-of-function mutation (p.F272S) in the GPR54 gene is associated with familial normosmic IHH. Underdeveloped external genitalia and impuberism point to the major role of GPR54 in the activation of the gonadotropic axis from intrauterine life to adulthood.

Copy number variation associated with Kallmann syndrome: new genetics insights from genome-wide studies

Kallmann syndrome and normosmic isolated hypogonadotropic hypogonadism (IHH) are developmental disorders characterized by hypogonadotropic hypogonadism that, in the former case, is coupled to loss of the sense of smell.1 Linkage analyses, deletion mapping and candidate gene approaches uncovered several loci in the pathogenetic mechanism of these diseases (Figure 1).2, 3 However, loss-of-function mutations in these genes account for only 30% of hypogonadotropic hypogonadism cases, suggesting that many disease-causing genes remain to be discovered.2, 3, 4 Copy number variations (CNVs) include inherited, de novo and somatically acquired deviations from a diploid state (deletions, duplications, insertions and complex genomic rearrangements) within a particular chromosomal segment. They usually are 1 kb in length or larger.5 Since the discovery of the important role of CNVs in human genome variability and also the recent development of high-resolution microarray-based technologies, a number of studies using these variants as genetic markers have emerged. Hence, CNVs are considered high risk factors for a considerable fraction of inherited and acquired diseases.5, 6, 7 Figure 1 Goals in the genetic etiology establishment of human hypogonadotropic hypogonadism: Kallmann syndrome and normosmic IHH. IHH, isolated hypogonadotropic hypogonadism. In Asian Journal of Andrology, a recent report by Zhang et al.8 provided some evidence for the potential involvement of CNVs in Kallmann syndrome. The authors used the array technology to investigate the genome-wide profile of structural variations in one consanguineous family with Kallmann syndrome.8 The results revealed that affected individuals had common CNVs (microdeletions) on five distinct chromosomal regions: 1p21.1, 2q32.2, 8q21.13, 14q21.2 and Xp22.31. Interestingly, the variant on Xp22.31 was found in an intronic region of KAL1, a gene responsible for X-linked form of Kallmann syndrome. Molecular testing for KAL1 (and also for FGFR1) was found to be normal,8 although alterations outside the exonic and splice site junction regions typically studied could not be excluded. In addition, genomic microdeletion in this Xp22.3 CNV was found in one of 29 Han Chinese sporadic Kallmann syndrome patients and in one of four other familial cases, but not in 26 Han Chinese sporadic normosmic IHH.8 Although the work of Zhang et al.8 was based in a very limited number of family members, the rare variants found only among the affected individuals account for a step further towards the better understanding of hypogonadotropic hypogonadism pathophysiology. For example, do the CNVs in the intronic region of KAL1 have any impact on these gene activities? Because CNVs are increasingly implicated in numerous diseases through a variety of mechanisms,5 it is possible that an intronic microdeletion disrupts control elements of splicing, leading to gene loss-of-function. Even though the intronic CNV in KAL1 gene variant was not found neither in healthy family members nor in a control population suggesting that possibly it is phenotypically unfavorable, the pathological relevance of this variant will merit further investigations. The paper also highlights the importance of CNVs in genome-wide projects to eventually help researchers to locate promising candidate genes for complex diseases. For instance, systematic exploration of CNVs in association studies have found susceptibility to HIV-1, lupus and Crohn's disease involving CNVs in CCL3L1, FCGR3B and C4, and DEFB4 genes, respectively (reviewed in Refs 5 and 7). Zhang et al.8 have also identified four autosomal CNVs that could be associated with Kallmann syndrome. However, we cannot exclude that these results represent false-positive findings; thus, replication is needed before one can conclude that these genomic regions contain genes that modulate human IHH. Accordingly, extensive genomic scanning for variations in new series of Kallmann syndrome and normosmic IHH could provide additional support for the results of Zhang et al.8 or underline other interesting regions related to IHH. It is undeniable that information provided by such studies is critical to improve our knowledge in the molecular basis of IHH and should be encouraged in years to come. The major challenge will be accurate interpretation of how genomic imbalances could be pathogenic in this disease.

Nonsense Mutations in FGF8 Gene Causing Different Degrees of Human Gonadotropin-Releasing Deficiency

FGFR1 mutations cause isolated hypogonadotropic hypogonadism (IHH) with or without olfactory abnormalities, Kallmann syndrome, and normosmic IHH respectively. Recently, missense mutations in FGF8, a key ligand for fibroblast growth factor (FGF) receptor 1 in the ontogenesis of GnRH, were identified in IHH patients, thus establishing FGF8 as a novel locus for human GnRH deficiency. Our objective was to analyze the clinical, hormonal, and molecular findings of two familial IHH patients due to FGF8 gene mutations. The entire coding region of the FGF8 gene was amplified and sequenced in two well-phenotyped IHH probands and their relatives. Two unique heterozygous nonsense mutations in FGF8 (p.R127X and p.R129X) were identified in two unrelated IHH probands, which were absent in 150 control individuals. These two mutations, mapped to the core domain of FGF8, impact all four human FGF8 isoforms, and lead to the deletion of a large portion of the protein, generating nonfunctional FGF8 ligands. The p.R127X mutation was identified in an 18-yr-old Kallmann syndrome female. Her four affected siblings with normosmic IHH or delayed puberty also carried the p.R127X mutation. Additional developmental anomalies, including cleft lip and palate and neurosensorial deafness, were also present in this family. The p.R129X mutation was identified in a 30-yr-old man with familial normosmic IHH and severe GnRH deficiency. We identified the first nonsense mutations in the FGF8 gene in familial IHH with variable degrees of GnRH deficiency and olfactory phenotypes, confirming that loss-of-function mutations in FGF8 cause human GnRH deficiency.

Nonsense Mutations inFGF8Gene Causing Different Degrees of Human Gonadotropin-Releasing Deficiency

FGFR1 mutations cause isolated hypogonadotropic hypogonadism (IHH) with or without olfactory abnormalities, Kallmann syndrome, and normosmic IHH respectively. Recently, missense mutations in FGF8, a key ligand for fibroblast growth factor receptor (FGFR) 1 in the ontogenesis of GnRH, were identified in IHH patients, thus establishing FGF8 as a novel locus for human GnRH deficiency. Our objective was to analyze the clinical, hormonal, and molecular findings of two familial IHH patients due to FGF8 gene mutations. The entire coding region of the FGF8 gene was amplified and sequenced in two well-phenotyped IHH probands and their relatives. Two unique heterozygous nonsense mutations in FGF8 (p.R127X and p.R129X) were identified in two unrelated IHH probands, which were absent in 150 control individuals. These two mutations, mapped to the core domain of FGF8, impact all four human FGF8 isoforms, and lead to the deletion of a large portion of the protein, generating nonfunctional FGF8 ligands. The p.R127X mutation was identified in an 18-yr-old Kallmann syndrome female. Her four affected siblings with normosmic IHH or delayed puberty also carried the p.R127X mutation. Additional developmental anomalies, including cleft lip and palate and neurosensorial deafness, were also present in this family. The p.R129X mutation was identified in a 30-yr-old man with familial normosmic IHH and severe GnRH deficiency. We identified the first nonsense mutations in the FGF8 gene in familial IHH with variable degrees of GnRH deficiency and olfactory phenotypes, confirming that loss-of-function mutations in FGF8 cause human GnRH deficiency.

Mutations of the KISS1 Gene Associated with Central Precocious Puberty

Context: Kisspeptin, encoded by the KISS1 gene, is a key stimulatory factor of GnRH secretion and puberty onset. Inactivating mutations of its receptor (KISS1R) cause isolated hypogonadotropic hypogonadism (IHH). A unique KISS1R activating mutation was described in central precocious puberty (CPP). Objective: To investigate KISS1 mutations in patients with idiopathic CPP and normosmic IHH. Patients: Eighty-three children with CPP (77 girls) and 61 patients with IHH (40 men) were studied. The control group consisted of 200 individuals with normal pubertal development. Methods: The promoter region and the 3 exons of KISS1 were amplified and sequenced. Cells expressing KISS1R were stimulated with synthetic human wild-type or mutant kisspeptin-54 (kp54) and inositol phosphate accumulation was measured. In a second set of experiments, kp54 was pre-incubated in human serum prior to stimulation of the cells. Results: Two novel KISS1 missense mutations, p.P74S and p.H90D, were identified in three unrelated children with idiopathic CPP. Both mutations were absent in 400 control alleles. The p.P74S mutation was identified in the heterozygous state in a boy who developed CPP at 1 yr of age. The p.H90D mutation was identified in the homozygous state in two unrelated girls with CPP. In vitro studies revealed that the capacity of the P74S and H90D mutants to stimulate IP production was similar to the wild-type. After pre-incubation of wild-type and mutant kp54’s in human serum, the capacity to stimulate signal transduction was significantly greater for P74S compared to the wild-type, suggesting that the p.P74S variant is more stable. Only polymorphisms were found in the IHH group. Conclusion: Two KISS1 mutations were identified in unrelated patients with idiopathic CPP. The p.P74S variant was associated with higher kisspeptin resistance to degradation in comparison to the wild-type, suggesting a role for this mutation in the precocious puberty phenotype. Infants of Women with Polycystic Ovary Syndrome have Lower Cord Blood Androstenedione and Estradiol Levels Helen Anderson, Naomi Fogel, Stefan K. Grebe, Ravinder J. Singh, Robert L. Taylor, and Andrea Dunaif (J Clin Endocrinol Metab, 10.1210/jc.2009-2651) ABSTRACT Context: Prenatal androgen excess can cause a phenocopy of polycystic ovary syndrome (PCOS) in mammals. Retrospective studies have suggested that girls at risk for PCOS have low birth weight and prospective studies have suggested an increased prevalence of small for gestational age offspring in women with PCOS. Objective: To determine whether infants of women with PCOS have reduced birth weight or increased intrauterine androgen levels. Design: Prospective case-control study. Endocrine Reviews, April 2010, 31(2):254–263 edrv.endojournals.org 255Context: Prenatal androgen excess can cause a phenocopy of polycystic ovary syndrome (PCOS) in mammals. Retrospective studies have suggested that girls at risk for PCOS have low birth weight and prospective studies have suggested an increased prevalence of small for gestational age offspring in women with PCOS. Objective: To determine whether infants of women with PCOS have reduced birth weight or increased intrauterine androgen levels. Design: Prospective case-control study. Endocrine Reviews, April 2010, 31(2):254–263 edrv.endojournals.org 255

Mutations of the KISS1 Gene in Disorders of Puberty

Kisspeptin, encoded by the KISS1 gene, is a key stimulatory factor of GnRH secretion and puberty onset. Inactivating mutations of its receptor (KISS1R) cause isolated hypogonadotropic hypogonadism (IHH). A unique KISS1R-activating mutation was described in central precocious puberty (CPP). Our objective was to investigate KISS1 mutations in patients with idiopathic CPP and normosmic IHH. Eighty-three children with CPP (77 girls) and 61 patients with IHH (40 men) were studied. The control group consisted of 200 individuals with normal pubertal development. The promoter region and the three exons of KISS1 were amplified and sequenced. Cells expressing KISS1R were stimulated with synthetic human wild-type or mutant kisspeptin-54 (kp54), and inositol phosphate accumulation was measured. In a second set of experiments, kp54 was preincubated in human serum before stimulation of the cells. Two novel KISS1 missense mutations, p.P74S and p.H90D, were identified in three unrelated children with idiopathic CPP. Both mutations were absent in 400 control alleles. The p.P74S mutation was identified in the heterozygous state in a boy who developed CPP at 1 yr of age. The p.H90D mutation was identified in the homozygous state in two unrelated girls with CPP. In vitro studies revealed that the capacity of the P74S and H90D mutants to stimulate IP production was similar to the wild type. After preincubation of wild-type and mutant kp54 in human serum, the capacity to stimulate signal transduction was significantly greater for P74S compared with the wild type, suggesting that the p.P74S variant is more stable. Only polymorphisms were found in the IHH group. Two KISS1 mutations were identified in unrelated patients with idiopathic CPP. The p.P74S variant was associated with higher kisspeptin resistance to degradation in comparison with the wild type, suggesting a role for this mutation in the precocious puberty phenotype.

Novel Fibroblast Growth Factor Receptor 1 Mutations in Patients with Congenital Hypogonadotropic Hypogonadism with and without Anosmia

Kallmann syndrome is a clinically and genetically heterogeneous disorder. To date, loss-of-function mutations in the genes encoding anosmin-1 (KAL1) and fibroblast growth factor receptor 1 (FGFR1) have been described in the X-linked and autosomal dominant forms of this syndrome, respectively. The objective was to investigate genetic defects in the KAL1 and FGFR1 genes in patients with congenital isolated hypogonadotropic hypogonadism (IHH). Eighty patients (71 males and nine females) with IHH were studied, of which 30 were familial. Forty-six of them had olfactory abnormalities. The coding regions of both KAL1 and FGFR1 genes were amplified and automatically sequenced. The KAL1 mutations were investigated only in patients with olfactory abnormalities, whereas FGFR1 was studied in the entire group. Two novel KAL1 mutations, an intragenic deletion of exons 3-6 and a splicing mutation IVS7 + 1G>A, were identified in two of 46 patients with Kallmann syndrome. Eight novel heterozygous FGFR1 mutations (G48S, L245P, R250W, A343V, P366L, K618fsX654, P722S, and V795I) were identified in nine of 80 patients with IHH. Eight of them had olfactory abnormalities. Interestingly, the G48S mutation was identified in a normosmic IHH patient. Two unrelated females, who carried FGFR1 mutations, had anosmia and normal reproductive function. We identified novel mutations in KAL1 and FGFR1 genes in IHH patients. FGFR1 mutations were identified in 17% of the patients with olfactory abnormalities and in one of 34 normosmic IHH patients. In addition, isolated anosmia was identified in two unrelated females as a partial phenotypic manifestation of FGFR1 defects.