Genetic overlap in Kallmann syndrome, combined pituitary hormone deficiency, and septo-optic dysplasia

Pathogenic copy number variants in patients with congenital hypopituitarism associated with complex phenotypes

OBJECTIVES

The aetiology of congenital hypopituitarism (CH) is unknown in most patients. Rare copy number variants (CNVs) have been implicated as the cause of genetic syndromes with previously unknown aetiology. Our aim was to study the presence of CNVs and their pathogenicity in patients with idiopathic CH associated with complex phenotypes.

DESIGN AND PATIENTS

We selected 39 patients with syndromic CH for array-based comparative genomic hybridization (aCGH). Patients with pathogenic CNVs were also evaluated by whole exome sequencing.

RESULTS

Twenty rare CNVs were detected in 19 patients. Among the identified rare CNVs, six were classified as benign, eleven as variants of uncertain clinical significance (VUS) and four as pathogenic. The three patients with pathogenic CNVs had combined pituitary hormone deficiencies, and the associated complex phenotypes were intellectual disabilities: trichorhinophalangeal type I syndrome (TRPS1) and developmental delay/intellectual disability with cardiac malformation, respectively. Patient one has a de novo 1.6-Mb deletion located at chromosome 3q13.31q13.32, which overlaps with the region of the 3q13.31 deletion syndrome. Patient two has a 10.5-Mb de novo deletion at 8q23.1q24.11, encompassing the TRPS1 gene; his phenotype is compatible with TRPS1. Patient three carries a chromosome translocation t(2p24.3;4q35.1) resulting in two terminal alterations: a 2p25.3p24.3 duplication of 14.7 Mb and a 4-Mb deletion at 4q35.1q35.2.

CONCLUSIONS

Copy number variants explained the phenotype in 8% of patients with hypopituitarism and additional complex phenotypes. This suggests that chromosomal alterations are an important contributor to syndromic hypopituitarism.

Clues for Polygenic Inheritance of Pituitary Stalk Interruption Syndrome From Exome Sequencing in 20 Patients

CONTEXT

Pituitary stalk interruption syndrome (PSIS) consists of a small/absent anterior pituitary lobe, an interrupted/absent pituitary stalk, and an ectopic posterior pituitary lobe. Mendelian forms of PSIS are detected infrequently (<5%), and a polygenic etiology has been suggested. GLI2 variants have been reported at a relatively high frequency in PSIS.

OBJECTIVE

To provide further evidence for a non-Mendelian, polygenic etiology of PSIS.

METHODS

Exome sequencing (trio approach) in 20 patients with isolated PSIS. In addition to searching for (potentially) pathogenic de novo and biallelic variants, a targeted search was performed in a panel of genes associated with midline brain development (223 genes). For GLI2 variants, both (potentially) pathogenic and relatively rare variants (<5% in the general population) were studied. The frequency of GLI2 variants was compared with that of a reference population.

RESULTS

We found four additional candidate genes for isolated PSIS (DCHS1, ROBO2, CCDC88C, and KIF14) and one for syndromic PSIS (KAT6A). Eleven GLI2 variants were present in six patients. A higher frequency of a combination of two GLI2 variants (M1352V + D1520N) was found in the study group compared with a reference population (10% vs 0.68%). (Potentially) pathogenic variants were identified in genes associated with midline brain anomalies, including holoprosencephaly, hypogonadotropic hypogonadism, and absent corpus callosum and in genes involved in ciliopathies.

CONCLUSION

Combinations of variants in genes associated with midline brain anomalies are frequently present in PSIS and sustain the hypothesis of a polygenic cause of PSIS.

Sexually dimorphic distribution of Prokr2 neurons revealed by the Prokr2-Cre mouse model

Prokineticin receptor 2 (PROKR2) is predominantly expressed in the mammalian central nervous system. Loss-of-function mutations of PROKR2 in humans are associated with Kallmann syndrome due to the disruption of gonadotropin releasing hormone neuronal migration and deficient olfactory bulb morphogenesis. PROKR2 has been also implicated in the neuroendocrine control of GnRH neurons post-migration and other physiological systems. However, the brain circuitry and mechanisms associated with these actions have been difficult to investigate mainly due to the widespread distribution of Prokr2-expressing cells, and the lack of animal models and molecular tools. Here, we describe the generation, validation and characterization of a new mouse model that expresses Cre recombinase driven by the Prokr2 promoter, using CRISPR-Cas9 technology. Cre expression was visualized using reporter genes, tdTomato and GFP, in males and females. Expression of Cre-induced reporter genes was found in brain sites previously described to express Prokr2, e.g., the paraventricular and the suprachiasmatic nuclei, and the area postrema. The Prokr2-Cre mouse model was further validated by colocalization of Cre-induced GFP and Prokr2 mRNA. No disruption of Prokr2 expression, GnRH neuronal migration or fertility was observed. Comparative analysis of Prokr2-Cre expression in male and female brains revealed a sexually dimorphic distribution confirmed by in situ hybridization. In females, higher Cre activity was found in the medial preoptic area, ventromedial nucleus of the hypothalamus, arcuate nucleus, medial amygdala and lateral parabrachial nucleus. In males, Cre was higher in the amygdalo-hippocampal area. The sexually dimorphic pattern of Prokr2 expression indicates differential roles in reproductive function and, potentially, in other physiological systems.

Hypogonadotropic Hypogonadism due to Novel FGFR1 Mutations

OBJECTIVE

The underlying genetic etiology of hypogonadotropic hypogonadism (HH) is heterogeneous. Fibroblast growth factor signaling is pivotal in the ontogeny of gonadotropin-releasing hormone neurons. Loss-of-function mutations in FGFR1 gene cause variable HH phenotypes encompassing pubertal delay to idiopathic HH (IHH) or Kallmann syndrome (KS). As FGFR1 mutations are common, recognizing mutations and associated phenotypes may enhance clinical management.

METHODS

Using a candidate gene approach, we screened 52 IHH/KS patients.

RESULTS

We identified three novel (IVS3-1G>C and p.W2X, p.R209C) FGFR1 gene mutations. Despite predictive null protein function, patients from the novel mutation families had normosmic IHH without non-reproductive phenotype.

CONCLUSION

These findings further emphasize the great variability of FGFR1 mutation phenotypes in IHH/KS.

The multiple genetic causes of central hypothyroidism

An insufficient stimulation by thyrotropin (TSH) of an otherwise normal thyroid gland represents the cause of Central Hypothyrodism (CeH). CeH is about 1000-folds rarer than Primary Hypothyroidism and often represents a real challenge for the clinicians, mainly because they cannot rely on adequately sensitive parameters for diagnosis or management, as it occurs with circulating TSH in PH. Therefore, CeH diagnosis can be frequently missed or delayed in patients with a previously unknown pituitary involvement. A series of genetic defects have been described to account for isolated CeH or combined pituitary hormone defects (CPHDs) with variable clinical characteristics and degrees of severity. The recently identified candidate gene IGSF1 appears frequently involved. This review provides an updated illustration of the different genetic defects accounting for CeH.

PITUITARY STALK INTERRUPTION SYNDROME: REPORT OF TWO CASES AND LITERATURE REVIEW

Pituitary stalk interruption syndrome (PSIS) consisting of the triad: ectopic posterior pituitary (EPP), thin or absent pituitary stalk and anterior pituitary hypoplasia is a rare pituitary malformation with variable degrees of pituitary insufficiency, from isolated growth hormone deficiency to TSH, gonadotropin and ACTH deficiency which may occur in time, with normo, hyper or hypoprolactinemia and central diabetes insipidus in up to 10% of cases. Also, extrapituitary malformations have been described in some cases. Genetic defects were identified only in 5% of cases. MRI findings are considered predictive for the endocrine phenotype. We aim to describe two cases with PSIS without central diabetes insipidus, anosmia and extrapituitary malformations, except for minor head dysmorphic features. The first case was referred at the age of 4 years for short stature (-4SDS for height, bone age 2 years), diagnosed with severe GH deficiency and developed central hypothyroidism and hypoprolactinemia during five-years follow-up. The second case, a 26 year old male with birth asphyxia, cryptorchidism, poor growth in childhood and adolescence (-3 to -4 height SDS), absent puberty and normal adult height (-1.18 SDS; bone age 15.5 years and active growth plates) had GH, TSH, ACTH deficiency and low normal PRL levels. Increasing medical awareness on PSIS clinical and endocrine heterogeneity may help a more early and accurate diagnosis. Corroboration of neuroimaging and endocrine data will improve our knowledge and understanding and will create premises for molecular diagnosis, genetic counseling and a better patients' management.

Genetics of Combined Pituitary Hormone Deficiency: Roadmap into the Genome Era

The genetic basis for combined pituitary hormone deficiency (CPHD) is complex, involving 30 genes in a variety of syndromic and nonsyndromic presentations. Molecular diagnosis of this disorder is valuable for predicting disease progression, avoiding unnecessary surgery, and family planning. We expect that the application of high throughput sequencing will uncover additional contributing genes and eventually become a valuable tool for molecular diagnosis. For example, in the last 3 years, six new genes have been implicated in CPHD using whole-exome sequencing. In this review, we present a historical perspective on gene discovery for CPHD and predict approaches that may facilitate future gene identification projects conducted by clinicians and basic scientists. Guidelines for systematic reporting of genetic variants and assigning causality are emerging. We apply these guidelines retrospectively to reports of the genetic basis of CPHD and summarize modes of inheritance and penetrance for each of the known genes. In recent years, there have been great improvements in databases of genetic information for diverse populations. Some issues remain that make molecular diagnosis challenging in some cases. These include the inherent genetic complexity of this disorder, technical challenges like uneven coverage, differing results from variant calling and interpretation pipelines, the number of tolerated genetic alterations, and imperfect methods for predicting pathogenicity. We discuss approaches for future research in the genetics of CPHD.

Genetic causes of isolated and combined pituitary hormone deficiency

Research over the last 20 years has led to the elucidation of the genetic aetiologies of Isolated Growth Hormone Deficiency (IGHD) and Combined Pituitary Hormone Deficiency (CPHD). The pituitary plays a central role in growth regulation, coordinating the multitude of central and peripheral signals to maintain the body's internal balance. Naturally occurring mutation in humans and in mice have demonstrated a role for several factors in the aetiology of IGHD/CPHD. Mutations in the GH1 and GHRHR genes shed light on the phenotype and pathogenesis of IGHD whereas mutations in transcription factors such as HESX1, PROP1, POU1F1, LHX3, LHX4, GLI2 and SOX3 contributed to the understanding of CPHD. Depending upon the expression patterns of these molecules, the phenotype may consist of isolated hypopituitarism, or more complex disorders such as septo-optic dysplasia (SOD) and holoprosencephaly. Although numerous monogenic causes of growth disorders have been identified, most of the patients with IGHD/CPHD remain with an explained aetiology as shown by the relatively low mutation detection rate. The introduction of novel diagnostic approaches is now leading to the disclosure of novel genetic causes in disorders characterized by pituitary hormone defects.

Reassessment of Genomic Sequence Variation to Harmonize Interpretation for Personalized Medicine

Accurate interpretation of DNA sequence variation is a prerequisite for implementing personalized medicine. Discrepancies in interpretation between testing laboratories impede the effective use of genetic test results in clinical medicine. To better understand the underpinnings of these discrepancies, we quantified differences in variant classification internally over time and those between our diagnostic laboratory and other laboratories and resources. We assessed the factors that contribute to these discrepancies and those that facilitate their resolution. Our process resolved 72% of nearly 300 discrepancies between pairs of laboratories to within a one-step classification difference and identified key sources of data that facilitate changes in variant interpretation. The identification and harmonization of variant discrepancies will maximize the clinical use of genetic information; these processes will be fostered by the accumulation of additional population data as well as the sharing of data between diagnostic laboratories.

Oligomerization of GPCRs involved in endocrine regulation

More than 800 different human membrane-spanning G-protein-coupled receptors (GPCRs) serve as signal transducers at biological barriers. These receptors are activated by a wide variety of ligands such as peptides, ions and hormones, and are able to activate a diverse set of intracellular signaling pathways. GPCRs are of central importance in endocrine regulation, which underpins the significance of comprehensively studying these receptors and interrelated systems. During the last decade, the capacity for multimerization of GPCRs was found to be a common and functionally relevant property. The interaction between GPCR monomers results in higher order complexes such as homomers (identical receptor subtype) or heteromers (different receptor subtypes), which may be present in a specific and dynamic monomer/oligomer equilibrium. It is widely accepted that the oligomerization of GPCRs is a mechanism for determining the fine-tuning and expansion of cellular processes by modification of ligand action, expression levels, and related signaling outcome. Accordingly, oligomerization provides exciting opportunities to optimize pharmacological treatment with respect to receptor target and tissue selectivity or for the development of diagnostic tools. On the other hand, GPCR heteromerization may be a potential reason for the undesired side effects of pharmacological interventions, faced with numerous and common mutual signaling modifications in heteromeric constellations. Finally, detailed deciphering of the physiological occurrence and relevance of specific GPCR/GPCR-ligand interactions poses a future challenge. This review will tackle the aspects of GPCR oligomerization with specific emphasis on family A GPCRs involved in endocrine regulation, whereby only a subset of these receptors will be discussed in detail.

Novel Mutations in HESX1 and PROP1 Genes in Combined Pituitary Hormone Deficiency

BACKGROUND/AIMS

The HESX1 gene is essential in forebrain development and pituitary organogenesis, and its mutations are the most commonly identified genetic cause of septo-optic dysplasia (SOD). The PROP1 gene is involved in anterior pituitary cell lineage specification and is commonly implicated in non-syndromic combined pituitary hormone deficiency (CPHD). We aimed to assess the involvement of HESX1 and PROP1 mutations in a cohort of patients with SOD and CPHD.

METHODS

Six patients with sporadic SOD and 16 patients with CPHD from 14 pedigrees were screened for mutations in HESX1 and PROP1 genes by exon sequencing. Half of the CPHD patients had variable associated clinical characteristics, such as hearing loss, orofacial cleft, kidney disorder or developmental delay. Novel variants were evaluated in silico and verified in SNP databases.

RESULTS

A novel heterozygous p.Glu102Gly mutation in the HESX1 gene and a novel homozygous p.Arg121Thr mutation in the PROP1 gene were detected in 2 pedigrees with CPHD. A small previously reported deletion in PROP1 c.301_302delAG was detected in a separate patient with CPHD, in heterozygous state. No mutations were identified in patients with SOD.

CONCLUSIONS

Our results expand the spectrum of mutations implicated in CPHD. The frequency of 15% of the PROP1 mutations in CPHD was low, likely due to the clinical heterogeneity of the cohort.

MECHANISMS IN ENDOCRINOLOGY: An update in the genetic aetiologies of combined pituitary hormone deficiency

Over the last 5 years, new actors involved in the pathogenesis of combined pituitary hormone deficiency in humans have been reported: they included a member of the immunoglobulin superfamily glycoprotein and ciliary G protein-coupled receptors, as well as new transcription factors and signalling molecules. New modes of inheritance for alterations of genes encoding transcription factors have also been described. Finally, actors known to be involved in a very specific phenotype (hypogonadotroph hypogonadism for instance) have been identified in a wider range of phenotypes. These data thus suggest that new mechanisms could explain the low rate of aetiological identification in this heterogeneous group of diseases. Taking into account the fact that several reviews have been published in recent years on classical aetiologies of CPHD such as mutations of POU1F1 or PROP1, we focused the present overview on the data published in the last 5 years, to provide the reader with an updated review on this rapidly evolving field of knowledge.

A novel mutation in HESX1 causes combined pituitary hormone deficiency without septo optic dysplasia phenotypes

Heterozygous and/or homozygous HESX1 mutations have been reported to cause isolated growth hormone deficiency (IGHD) or combined pituitary hormone deficiency (CPHD), in association with septo optic dysplasia (SOD). We report a novel heterozygous HESX1 mutation in a CPHD patient without SOD phenotypes. The propositus was a one-year-old Japanese girl. Shortly after birth, she was found to be hypoglycemic. She was diagnosed with central adrenal insufficiency based on low cortisol and ACTH at a time of severe hypoglycemia. Further endocrine studies indicated that the patient also had central hypothyroidism and growth hormone deficiency. Using a next-generation sequencing strategy, we identified a novel heterozygous HESX1 mutation, c.326G>A (p.Arg109Gln). Western blotting and subcellular localization revealed no significant difference between wild type and mutant HESX1. Electrophoretic mobility shift assays showed that the mutant HESX1 abrogated DNA-binding ability. Mutant HESX1 was unable to repress PROP1-mediated activation. In conclusion, this study identified Arg109 as a critical residue in the HESX1 protein and extends our understanding of the phenotypic features, molecular mechanism, and developmental course associated with mutations in HESX1. When multiple genes need to be analyzed for mutations simultaneously, targeted sequence analysis of interesting genomic regions is an attractive approach.

Natural history of growth hormone deficiency in a pediatric cohort

BACKGROUND/AIMS

Controversies still exist regarding the evaluation of growth hormone deficiency (GHD) in childhood at the end of growth. The aim of this study was to describe the natural history of GHD in a pediatric cohort.

METHODS

This is a retrospective study of a cohort of pediatric patients with GHD. Cases of acquired GHD were excluded. Univariate logistic regression was used to identify predictors of GHD persisting into adulthood.

RESULTS

Among 63 identified patients, 47 (75%) had partial GHD at diagnosis, while 16 (25%) had complete GHD, including 5 with multiple pituitary hormone deficiencies. At final height, 50 patients underwent repeat stimulation testing; 28 (56%) recovered and 22 (44%) remained growth hormone (GH) deficient. Predictors of persisting GHD were: complete GHD at diagnosis (OR 10.1, 95% CI 2.4-42.1), pituitary stalk defect or ectopic pituitary gland on magnetic resonance imaging (OR 6.5, 95% CI 1.1-37.1), greater height gain during GH treatment (OR 1.8, 95% CI 1.0-3.3), and IGF-1 level <-2 standard deviation scores (SDS) following treatment cessation (OR 19.3, 95% CI 3.6-103.1). In the multivariate analysis, only IGF-1 level <-2 SDS (OR 13.3, 95% CI 2.3-77.3) and complete GHD (OR 6.3, 95% CI 1.2-32.8) were associated with the outcome.

CONCLUSION

At final height, 56% of adolescents with GHD had recovered. Complete GHD at diagnosis, low IGF-1 levels following retesting, and pituitary malformation were strong predictors of persistence of GHD.

Novel application of luciferase assay for the in vitro functional assessment of KAL1 variants in three females with septo-optic dysplasia (SOD)

KAL1 is implicated in 5% of Kallmann syndrome cases, a disorder which genotypically overlaps with septo-optic dysplasia (SOD). To date, a reporter-based assay to assess the functional consequences of KAL1 mutations is lacking. We aimed to develop a luciferase assay for novel application to functional assessment of rare KAL1 mutations detected in a screen of 422 patients with SOD. Quantitative analysis was performed using L6-myoblasts stably expressing FGFR1, transfected with a luciferase-reporter vector containing elements of the FGF-responsive osteocalcin promoter. The two variants assayed [p.K185N, p.P291T], were detected in three females with SOD (presenting with optic nerve hypoplasia, midline and pituitary defects). Our novel assay revealed significant decreases in transcriptional activity [p.K185N: 21% (p < 0.01); p.P291T: 40% (p < 0.001)]. Our luciferase-reporter assay, developed for assessment of KAL1 mutations, determined that two variants in females with hypopituitarism/SOD are loss-of-function; demonstrating that this assay is suitable for quantitative assessment of mutations in this gene.

Frequency of genetic defects in combined pituitary hormone deficiency: a systematic review and analysis of a multicentre Italian cohort

OBJECTIVE

Combined pituitary hormonal deficiency (CPHD) can result from mutations within genes that encode transcription factors. This study evaluated the frequency of mutations in these genes in a cohort of 144 unrelated Italian patients with CPHD and estimated the overall prevalence of mutations across different populations using a systematic literature review.

MATERIAL AND METHODS

A multicentre study of adult and paediatric patients with CPHD was performed. The PROP1, POU1F1, HESX1, LHX3 and LHX4 genes were analysed for the presence of mutations using direct sequencing. We systematically searched PubMed with no date restrictions for studies that reported genetic screening of CPHD cohorts. We only considered genetic screenings with at least 10 individuals. Data extraction was conducted in accordance with the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

Global mutation frequency in Italian patients with CPHD was 2·9% (4/136) in sporadic cases and 12·5% (1/8) in familial cases. The worldwide mutation frequency for the five genes calculated from 21 studies was 12·4%, which ranged from 11·2% in sporadic to 63% in familial cases. PROP1 was the most frequently mutated gene in sporadic (6·7%) and familial cases (48·5%).

CONCLUSION

The frequency of defects in genes encoding pituitary transcription factors is quite low in Italian patients with CPHD and other western European countries, especially in sporadic patients. The decision of which genes should be tested and in which order should be guided by hormonal and imaging phenotype, the presence of extrapituitary abnormalities and the frequency of mutation for each gene in the patient-referring population.

Kallmann syndrome patient with gender dysphoria, multiple sclerosis, and thrombophilia

One of the challenging issues in patients with complex problems is that the various diseases and their treatment can influence each other and present unusual hurdles in management. We investigated one such complex case. A 34-year-old XY male presented with azoospermia, detected on semen analysis for pre-orchidectomy sperm banking. He had a 20-year history of gender dysphoria and bilateral breast swelling. The patient suffered a deep vein thrombosis at the age of 19 years. Examination confirmed clinical features of Kallmann syndrome including unilateral cryptorchidism, micropenis, congenital anosmia, and bimanual synkinesis (mirror movements), with reduced serum testosterone and normal gonadotropin levels demonstrating hypogonadotropic hypogonadism. MRI showed missing olfactory bulbs. Osteopenia and reduced vitamin D levels of 21 nmol/L were identified. He was found to harbor a heterozygous factor-V-Leiden mutation. The genetic basis of Kallmann syndrome remains unknown: his screening tests were negative for mutations in CHD7, FGF8, FGFR1, GNRH1, GNRHR, HS6ST1, KAL1, KISS1R, KISS1, NELF, PROK2, PROKR2, TAC3, and TACR3. The patient initially declined testosterone therapy with a view to undergo gender reassignment. Over the next 2 years, the patient experienced recurrent episodes of weakness and paresthesia, associated with classical MRI appearances of multiple sclerosis-related demyelination in the spinal cord and brain. Although it was difficult to elucidate an association between the patient's gender dysphoria and untreated congenital hypogonadism, his desire to become female together with his co-existing thrombophilia, presented challenges to the administration of hormone treatment. Furthermore, we have considered an association between multiple sclerosis and hypogonadotropic hypogonadism.

60 YEARS OF NEUROENDOCRINOLOGY: The hypothalamo-GH axis: the past 60 years

At the time of the publication of Geoffrey Harris's monograph on 'Neural control of the pituitary gland' 60 years ago, the pituitary was recognised to produce a growth factor, and extracts administered to children with hypopituitarism could accelerate growth. Since then our understanding of the neuroendocrinology of the GH axis has included identification of the key central components of the GH axis: GH-releasing hormone and somatostatin (SST) in the 1970s and 1980s and ghrelin in the 1990s. Characterisation of the physiological control of the axis was significantly advanced by frequent blood sampling studies in the 1980s and 1990s; the pulsatile pattern of GH secretion and the factors that influenced the frequency and amplitude of the pulses have been defined. Over the same time, spontaneously occurring and targeted mutations in the GH axis in rodents combined with the recognition of genetic causes of familial hypopituitarism demonstrated the key factors controlling pituitary development. As the understanding of the control of GH secretion advanced, developments of treatments for GH axis disorders have evolved. Administration of pituitary-derived human GH was followed by the introduction of recombinant human GH in the 1980s, and, more recently, by long-acting GH preparations. For GH excess disorders, dopamine agonists were used first followed by SST analogues, and in 2005 the GH receptor blocker pegvisomant was introduced. This review will cover the evolution of these discoveries and build a picture of our current understanding of the hypothalamo-GH axis.

Congenital combined pituitary hormone deficiency patients have better responses to gonadotrophin-induced spermatogenesis than idiopathic hypogonadotropic hypogonadism patients

STUDY QUESTION

Do patients with congenital combined pituitary hormone deficiency (CCPHD) have different responses to gonadotrophin-induced spermatogenesis compared with those with idiopathic hypogonadotropic hypogonadism (IHH)?

SUMMARY ANSWER

CCPHD patients have a better response to gonadotrophin therapy than IHH patients.

WHAT IS KNOWN ALREADY

Gonadotrophins are effective in inducing spermatogenesis in patients with hypogonadotropic hypogonadism.

DESIGN, SIZE AND DURATION

This retrospective cohort study included 75 patients, 53 of whom had IHH and 22 CCPHD. They were diagnosed, treated and followed up between January 2008 and December 2013.

PARTICIPANTS/MATERIALS, SETTING AND METHODS

Combined gonadotrophin therapy, consisting of human chorionic gonadotrophin and human menopausal gonadotrophin, was administered for 24 months. The success rate of spermatogenesis (≥1 sperm in ejaculate), serum total testosterone level, testicle size and sperm concentration during the treatment, as well as the first time sperm were detected in the ejaculate, were compared between the two diagnostic groups. All patients were treated in Peking Union Medical College Hospital.

MAIN RESULTS AND THE ROLE OF CHANCE

Spermatogenesis was successfully induced in 85% of IHH patients and 100% of CCPHD patients after 24-month combined gonadotrophin treatment (P = 0.03). In comparison with IHH, CCPHD patients had larger mean testicle sizes during the gonadotrophin treatment at 6, 12, 18 and 24 months (all P < 0.05). The initial time for sperm appearance in IHH group (n = 45) and CCPHD group (n = 22) was 13.2 ± 5.9 versus 10.4 ± 3.8 months (P = 0.045). Generally, CCPHD patients had higher sperm counts [median (quartiles)] than IHH patients during the treatment, but the difference was only statistically significant at 12 months of treatment, 3.3 (1.8, 12.0) versus 1.0 (0.0, 4.6) million/ml, P = 0.001. There was a higher level of serum total testosterone [mean (SD)] in the CCPHD group than the IHH group (676 ± 245 versus 555 ± 209 ng/dl, P = 0.035).

LIMITATIONS, REASONS FOR CAUTION

First, the inherent nature of a retrospective designed study was a main shortcoming. Secondly, pathological gene mutations in IHH and CCPHD patients should be further investigated. Clarification of the underlying mechanisms between cryptorchidism and mutated genes may provide more information for the divergent therapeutic responses between two groups. Only a minority of patients were actively seeking to have children so information about fertility is limited.

WIDER IMPLICATIONS OF THE FINDINGS

CCPHD patients had a lower incidence of cryptorchidism and a better response to gonadotrophin therapy than IHH patients, reflecting multiple defects on the different levels of reproduction axis in IHH. Furthermore, growth hormone is not indispensable for spermatogenesis in CCPHD patients.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by Natural Science Foundation of China (No: 81100416). None of the authors has any conflicts of interest to declare.

TRANSITION IN ENDOCRINOLOGY: Hypogonadism in adolescence

Puberty is a remarkable developmental process with the activation of the hypothalamic-pituitary-gonadal axis culminating in reproductive capacity. It is accompanied by cognitive, psychological, emotional, and sociocultural changes. There is wide variation in the timing of pubertal onset, and this process is affected by genetic and environmental influences. Disrupted puberty (delayed or absent) leading to hypogonadism may be caused by congenital or acquired etiologies and can have significant impact on both physical and psychosocial well-being. While adolescence is a time of growing autonomy and independence, it is also a time of vulnerability and thus, the impact of hypogonadism can have lasting effects. This review highlights the various forms of hypogonadism in adolescence and the clinical challenges in differentiating normal variants of puberty from pathological states. In addition, hormonal treatment, concerns regarding fertility, emotional support, and effective transition to adult care are discussed.

Pathology or normal variant: what constitutes a delay in puberty?

Puberty is a complex maturation process that begins during fetal life and persists until the acquisition of reproduction function. The fundamental event that activates puberty occurs in the hypothalamus. A complex neuron network stimulates GnRH secretion, which stimulates pituitary gonadotropin secretion and then gonadal steroid secretion. Pubertal delay is defined as the presentation of clinical signs of puberty 2-2.5 SD later than in the normal population. Three major groups of etiopathogeneses are described: (1) hypogonadotropic hypogonadism, (2) hypergonadotropic hypogonadism, and (3) constitutional delay of puberty (CDP) - the most common cause of delayed puberty in boys. The differential diagnosis between CDP and isolated hypogonadotropic hypogonadism remains difficult. Mechanisms of pubertal timing are now better understood and genetic or epigenetic causes can explain some pubertal delays. However, there are still unexplained mechanisms. Treatment of delayed puberty is necessary to ensure full pubertal development for the adolescent and in case of hypogonadism, to restore fertility. Finally, precocious diagnosis of hypogonadism is primordial but can be difficult during childhood and in cases of partial hypogonadism. The study of genetic pubertal diseases or of different animal models could help to discover new diagnostic or therapeutic tools.

FGFR1 and PROKR2 rare variants found in patients with combined pituitary hormone deficiencies

The genetic aetiology of congenital hypopituitarism (CH) is not entirely elucidated. FGFR1 and PROKR2 loss-of-function mutations are classically involved in hypogonadotrophic hypogonadism (HH), however, due to the clinical and genetic overlap of HH and CH; these genes may also be involved in the pathogenesis of CH. Using a candidate gene approach, we screened 156 Brazilian patients with combined pituitary hormone deficiencies (CPHD) for loss-of-function mutations in FGFR1 and PROKR2. We identified three FGFR1 variants (p.Arg448Trp, p.Ser107Leu and p.Pro772Ser) in four unrelated patients (two males) and two PROKR2 variants (p.Arg85Cys and p.Arg248Glu) in two unrelated female patients. Five of the six patients harbouring the variants had a first-degree relative that was an unaffected carrier of it. Results of functional studies indicated that the new FGFR1 variant p.Arg448Trp is a loss-of-function variant, while p.Ser107Leu and p.Pro772Ser present signalling activity similar to the wild-type form. Regarding PROKR2 variants, results from previous functional studies indicated that p.Arg85Cys moderately compromises receptor signalling through both MAPK and Ca(2) (+) pathways while p.Arg248Glu decreases calcium mobilization but has normal MAPK activity. The presence of loss-of-function variants of FGFR1 and PROKR2 in our patients with CPHD is indicative of an adjuvant and/or modifier effect of these rare variants on the phenotype. The presence of the same variants in unaffected relatives implies that they cannot solely cause the phenotype. Other associated genetic and/or environmental modifiers may play a role in the aetiology of this condition.

Fifty-Five Years of Pediatric Endocrinology and 50 Years of the Department of Pediatric Endocrinology, Diabetes and Metabolic Diseases in Slovenia

Paediatric endocrinology started its independent development early in the general development of this specialty, with a strong focus on research and clinical excellence. Slovenian paediatric endocrinology was an integral part of the European paediatric endocrinology from its beginnings and a founding member of the first ‘International Study Group for Diabetes in Children and Adolescents’. After the pioneering work of Prof. Lev Matajc, Prof. Ciril Kržišnik firmly integrated the Department of Pediatric Endocrinology, Diabetes and Metabolic Diseases at the University Children’s Hospital in Ljubljana in the international scientific community. In the last decade, the department participates in cutting-edge research and provides clinical services at highest international standards.

Expanding the phenotypic spectrum and variability of endocrine abnormalities associated with TUBB3 E410K syndrome

CONTEXT

A heterozygous de novo c.1228G>A mutation (E410K) in the TUBB3 gene encoding the neuronal-specific β-tubulin isotype 3 (TUBB3) causes the TUBB3 E410K syndrome characterized by congenital fibrosis of the extraocular muscles (CFEOM), facial weakness, intellectual and social disabilities, and Kallmann syndrome (anosmia with hypogonadotropic hypogonadism). All TUBB3 E410K subjects reported to date are sporadic cases.

OBJECTIVE

This study aimed to report the clinical, genetic, and molecular features of a familial presentation of the TUBB3 E410K syndrome.

DESIGN

Case report of a mother and three affected children with clinical features of the TUBB3 E410K syndrome.

SETTING

Academic Medical Center.

MAIN OUTCOME MEASURES

Genetic analysis of the TUBB3 gene and clinical evaluation of endocrine and nonendocrine phenotypes.

RESULTS

A de novo TUBB3 c.1228G>A mutation arose in a female proband who displayed CFEOM, facial weakness, intellectual and social disabilities, and anosmia. However, she underwent normal sexual development at puberty and had three spontaneous pregnancies with subsequent autosomal-dominant inheritance of the mutation by her three boys. All sons displayed nonendocrine features of the TUBB3 E410K syndrome similar to their mother but, in addition, had variable features suggestive of additional endocrine abnormalities.

CONCLUSIONS

This first report of an autosomal-dominant inheritance of the TUBB3 c.1228G>A mutation in a family provides new insights into the spectrum and variability of endocrine phenotypes associated with the TUBB3 E410K syndrome. These observations emphasize the need for appropriate clinical evaluation and complicate genetic counseling of patients and families with this syndrome.

Combined pituitary hormone deficiency with unique pituitary dysplasia and morning glory syndrome related to a heterozygous PROKR2 mutation

Recent reports have indicated the role of the prokineticin receptor 2 gene (PROKR2) in the etiology of congenital hypopituitarism, including septo-optic dysplasia and Kallmann syndrome. In the present study, using next-generation targeted sequencing, we identified a novel heterozygous PROKR2 variant (c.742C>T; p.R248W) in a female patient who had combined pituitary hormone deficiency (CPHD), morning glory syndrome and a severely malformed pituitary gland. No other mutation was present in 27 genes related to hypogonadotropic hypogonadism, pituitary hormone deficiency and optic nerve malformation. The substituted amino acid was located on the third intracellular loop of the PROKR2 protein, which is a G protein-coupled receptor. Computational analyses with two programs (SIFT and PolyPhen-2) showed that the substitution was deleterious to PROKR2 function. The p.R248W mutation was transmitted from the patient’s mother, who had a slightly delayed menarche. Collectively, we provide further genetic evidence linking heterozygous PROKR2 mutations and the development of CPHD.

De novo frameshift mutation in fibroblast growth factor 8 in a male patient with gonadotropin deficiency

BACKGROUND/AIMS

Missense, nonsense, and splice mutations in the Fibroblast Growth Factor 8(FGF8) have recently been identified in patients with hypothalamo-pituitary dysfunction and craniofacial anomalies. Here, we report a male patient with a frameshift mutation in FGF8.

CASE REPORT

The patient exhibited micropenis, craniofacial anomalies, and ventricular septal defect at birth. Clinical evaluation at 16 years and 8 months of age revealed delayed puberty, hyposmia, borderline mental retardation, and mild hearing difficulty. Endocrine findings included gonadotropin deficiency and primary hypothyroidism.

RESULTS

Molecular analysis identified a de novo heterozygous p.S192fsX204 mutation in the last exon of FGF8. RT-PCR analysis of normal human tissues detected FGF8 expression in the genital skin, and whole-mount in situ hybridization analysis of mouse embryos revealed Fgf8 expression in the anlage of the penis.

CONCLUSION

The results indicate that frameshift mutations in FGF8 account for a part of the etiology of hypothalamo-pituitary dysfunction. Micropenis in patients with FGF8 abnormalities appears to be caused by gonadotropin deficiency and defective outgrowth of the anlage of the penis.

Combined pituitary hormone deficiency: current and future status

Over the last two decades, the understanding of the mechanisms involved in pituitary ontogenesis has largely increased. Since the first description of POU1F1 human mutations responsible for a well-defined phenotype without extra-pituitary malformation, several other genetic defects of transcription factors have been reported with variable degrees of phenotype-genotype correlations. However, to date, despite the identification of an increased number of genetic causes of isolated or multiple pituitary deficiencies, the etiology of most (80-90 %) congenital cases of hypopituitarism remains unsolved. Identifying new etiologies is of importance as a post-natal diagnosis to better diagnose and treat the patients (delayed pituitary deficiencies, differential diagnosis of a pituitary mass on MRI, etc.), and as a prenatal diagnosis to decrease the risk of early death (undiagnosed corticotroph deficiency for instance). The aim of this review is to summarize the main etiologies and phenotypes of combined pituitary hormone deficiencies, associated or not with extra-pituitary anomalies, and to suggest how the identification of such etiologies could be improved in the near future.

Wasting syndrome with deep bradycardia as presenting manifestation of long-standing severe male hypogonadotropic hypogonadism: a case series

BACKGROUND

Physiological functioning of the testes is important for cardiac health besides for virilisation, physical strength, behavior and reproduction; moreover, hypogonadism has been demonstrated as a significant risk marker of increased all-cause and cardiovascular mortality.

CASES PRESENTATION

We reported two cases of long-standing hypogonadotropic hypogonadism presenting with wasting, bradycardia and heart failure. The two patients were admitted to emergency department for deep weakness, unresponsive anemia and severe bradycardia, requiring in one case the implanting of a monocameral pace-maker for treatment of heart failure. No previous cardiologic disorders were known and cardiac ischemia was ruled out in both patients. The first patient presented congenital hypogonadotropic hypogonadism combined with mild central hypothyroidism and growth hormone deficiency occurred in the peripubertal age, while the second one was diagnosed with isolated adult-onset severe central hypogonadism. Testosterone deficiency was the main feature in both patients as physical examination revealed clinical stigmata of hypogonadism and testosterone replacement induced a dramatic improvement of general condition. Genetic analysis of genes involved in hypogonadotropic hypogonadism failed to identify alterations.

CONCLUSION

Long-standing hypogonadism in males can be associated with life threatening body alterations including severe bradycardia and heart failure.

A novel KAL1 mutation is associated with combined pituitary hormone deficiency

Using a next-generation sequencing strategy, we identified a novel KAL1 missense mutation (p.His568Gln) in a patient with combined pituitary hormone deficiency, right microphthalmia, right renal aplasia and severe developmental delay. Our findings will provide additional evidence that KAL1 mutations are associated with hypopituitarism, in addition to luteinizing hormone, and follicle-stimulating hormone deficiencies, and improve our understanding of the phenotypic features and developmental course associated with KAL1 mutations.

Heterozygous FGF8 mutations in patients presenting cryptorchidism and multiple VATER/VACTERL features without limb anomalies

BACKGROUND

The acronym VATER/VACTERL association describes the combination of at least three of the following cardinal features: vertebral defects, anorectal malformations, cardiac defects, tracheoesophageal fistula with or without esophageal atresia, renal malformations, and limb defects. Although fibroblast growth factor-8 (FGF8) mutations have mainly found in patients with Kallmann syndrome, mice with a hypomorphic Fgf8 allele or complete gene invalidation display, aside from gonadotropin-releasing hormone deficiency, parts or even the entire spectrum of human VATER/VACTERL association.

METHODS

We performed FGF8 gene analysis in 49 patients with VATER/VACTERL association and 27 patients presenting with a VATER/VACTERL-like phenotype (two cardinal features).

RESULTS

We identified two heterozygous FGF8 mutations in patients displaying either VATER/VACTERL association (p.Gly29_Arg34dup) or a VATER/VACTERL-like phenotype (p.Pro26Leu) without limb anomalies. Whereas the duplication mutation has not been reported before, p.Pro26Leu was once observed in a Kallmann syndrome patient. Both our patients had additional bilateral cryptorchidism, a key phenotypic feature in males with FGF8 associated Kallmann syndrome. Each mutation was paternally inherited. Besides delayed puberty in both and additional unilateral cryptorchidism in one of the fathers, they were otherwise healthy. Serum hormone levels downstream the gonadotropin-releasing hormone in both patients and their fathers were within normal range.

CONCLUSION

Our results suggest FGF8 mutations to contribute to the formation of the VATER/VACTERL association. Further studies are needed to support this observation.

Midbrain-hindbrain involvement in septo-optic dysplasia

BACKGROUND AND PURPOSE

Midbrain-hindbrain involvement in septo-optic dysplasia has not been well described, despite reported mutations of genes regulating brain stem patterning. We aimed to describe midbrain-hindbrain involvement in patients with septo-optic dysplasia and to identify possible clinical-neuroimaging correlations.

MATERIALS AND METHODS

Using MR imaging, we categorized 38 patients (21 males) based on the presence (group A, 21 patients) or absence (group B, 17 patients) of visible brain stem anomalies. We measured height and anteroposterior diameter of midbrain, pons, and medulla, anteroposterior midbrain/pons diameter (M/P ratio), vermian height, and tegmento-vermian angle, and compared the results with 114 healthy age-matched controls. Furthermore, patients were subdivided based on the type of midline anomalies. The associations between clinical and neuroradiological features were investigated. Post hoc tests were corrected according to Bonferroni adjustment (pB).

RESULTS

Patients with brain stem abnormalities had smaller anteroposterior pons diameter than controls (pB < .0001) and group B (pB = .012), higher M/P ratio than controls (pB < .0001) and group B (pB < .0001), and smaller anteroposterior medulla diameter (pB = .001), pontine height (pB = .00072), and vermian height (pB = .0009) than controls. Six of 21 patients in group A had thickened quadrigeminal plate, aqueductal stenosis, and hydrocephalus; 3 also had agenesis of the epithalamus. One patient had a short midbrain with long pons and large superior vermis. There was a statistically significant association between brain stem abnormalities and callosal dysgenesis (P = .011) and developmental delay (P = .035), respectively.

CONCLUSION

Midbrain-hindbrain abnormalities are a significant, albeit underrecognized, component of the septo-optic dysplasia spectrum, and are significantly associated with developmental delay in affected patients.

Biased signaling through G-protein-coupled PROKR2 receptors harboring missense mutations

Various missense mutations in the gene coding for prokineticin receptor 2 (PROKR2), a G-protein-coupled receptor, have been identified in patients with Kallmann syndrome. However, the functional consequences of these mutations on the different signaling pathways of this receptor have not been studied. We first showed that the wild-type PROKR2 can activate different G-protein subtypes (Gq, Gs, and Gi/o) and recruit β-arrestins in transfected HEK-293 cells. We then examined, for each of these signaling pathways, the effects of 9 mutations that did not significantly impair cell surface targeting or ligand binding of the receptor. Four mutant receptors showing defective Gq signaling (R85C, R85H, R164Q, and V331M) could still recruit β-arrestins on ligand activation, which may cause biased signaling in vivo. Conversely, the R80C receptor could activate the 3 types of G proteins but could not recruit β-arrestins. Finally, the R268C receptor could recruit β-arrestins and activate the Gq and Gs signaling pathways but could not activate the Gi/o signaling pathway. Our results validate the concept that mutations in the genes encoding membrane receptors can bias downstream signaling in various ways, possibly leading to pathogenic and, perhaps in some cases, protective (e.g., R268C) effects.

Prenatal determinants of optic nerve hypoplasia: review of suggested correlates and future focus

Optic nerve hypoplasia (ONH), a congenital malformation characterized by an underdeveloped optic nerve, is a seemingly epidemic cause of childhood blindness and visual impairment with associated lifelong morbidity. Although the prenatal determinants of ONH are unknown, early case reports have led to a longstanding speculation that risky health behaviors (e.g., prenatal use of recreational drugs, alcohol) are a likely culprit. There has yet to be a systematic review of the epidemiology of ONH to assess the common prenatal features that may help focus research efforts in the identification of likely prenatal correlates. A review of the past 50 years of epidemiologic research was conducted to examine the prenatal features linked with ONH and provide direction for future research. There are select prominent prenatal features associated with ONH: young maternal age and primiparity. Commonly implicated prenatal exposures (recreational or pharmaceutical drugs, viral infection, etc.) were rare or uncommon in large cohort studies of ONH and therefore unlikely to be major contributors to ONH. Familial cases and gene mutations are rare. The preponderance of young mothers and primiparity among cases of ONH is striking, although the significance is unclear. Recent research suggests a potential role for prenatal nutrition, weight gain, and factors of deprivation. With the rapidly increasing prevalence of ONH, future research should focus on investigating the relevance of young maternal age and primiparity and exploring the recently suggested etiologic correlates in epidemic clusters of ONH.

Greater prevalence of PROKR2 mutations in Kallmann syndrome patients from the Maghreb than in European patients

CONTEXT

Kallmann syndrome (KS) is a genetically heterogeneous developmental disorder that associates hypogonadotropic hypogonadism and anosmia. Various causative genes have been identified, but their respective involvement in different world regions is poorly documented.

OBJECTIVE

We aimed to compare the prevalence of mutations in five routinely analyzed KS genes between Maghrebian and European patients.

METHODS

Blood samples from 120 presumably unrelated Maghrebian patients were collected for DNA sequencing by the Sanger technique. The prevalence of the non-synonymous mutations in KAL1, FGFR1, FGF8, PROKR2, and PROK2 was determined for each gene, and compared with those previously obtained from the analysis of 712 European patients.

RESULTS

Diverse mutations in PROKR2, a gene involved both in monogenic recessive and digenic/oligogenic KS transmission modes, were found in 23.3% of the Maghrebian patients, but only in 5.1% of the European patients (Fisher's exact test, P<0.001), whereas mutations in each of the other four KS genes were present either at similar frequencies in the Maghrebian and European patients (KAL1, PROK2, FGF8, from 6.6 to 0.8%; Fisher's exact test, P>0.4 for all comparisons) or at a lower frequency in Maghrebian patients (FGFR1, 5.0 vs 11.7%; Fisher's exact test, P<0.05). Homozygosity resulting from consanguineous marriages was not sufficient to account for the greater prevalence of PROKR2 mutations in the Maghrebian patients.

CONCLUSIONS

The great prevalence of PROKR2 mutations in Maghrebian patients has practical consequences for molecular diagnosis of the disease and genetic counseling in the Maghrebian population.

Suprasellar mass mimicking a hypothalamic glioma in a patient with a complete PROP1 deletion

Mutations in PROP1 are the most frequent defect detected in patients with combined pituitary hormone deficiency (MIM #262600), characterized by a clinical phenotype of proportionate growth deficit due to impaired production of growth hormone in combination with deficiency of one or more of the additional anterior pituitary hormones. Approximately one third of patients with PROP1 inactivating mutations present with abnormal development of the anterior lobe of the pituitary gland as revealed by MRI. We report on the clinical and molecular characterization of the fourth complete PROP1 deletion in a girl with proportional short stature, combined pituitary hormone deficiency and a suprasellar mass mimicking a hypothalamic glioma. The proband, born to consanguineous parents, presented with proportional growth failure (height 108.8 cm, -3.48 SDS), combined pituitary hormone deficiency (GH, TSH, PRL and gonadotropins) and a suprasellar mass with optic chiasm invasion, compatible with a diagnosis of chiasmatic hypothalamic glioma, as revealed by MRI. PROP1 mutation screening by PCR and MLPA detected a homozygous deletion of the entire PROP1. The deletion was delimited to at least 7.7 kb upstream of PROP1 and more finely to ∼541-74 bp downstream from PROP1 by aCGH and PCR mapping. We describe the fourth case with a complete PROP1 deletion in homozygosis. The apparent location of the respective 5' (within a highly repetitive region, rich in Alu sequences) and 3' (within an Alu sequence) breakpoints, suggests that the deletion may have arisen through homologous recombination. The differentiation between PROP1 mutation associated pituitary enlargements from craniopharyngioma, pituitary adenoma, dys-germinoma, or Rathke's pouch cyst, is critical for the correct patient management. It is important to recognize that PROP1 mutations can present associated with evolving pituitary masses and/or other MRI alterations of the pituitary during early childhood and that surgery is not indicated in these patients. Therefore, in the presence of combined pituitary hormone deficiency and a pituitary or hypothalamic mass, PROP1 analysis should be considered before referring the patient to a neurosurgeon.

FGFR1 mutations cause Hartsfield syndrome, the unique association of holoprosencephaly and ectrodactyly

Background

Harstfield syndrome is the rare and unique association of holoprosencephaly (HPE) and ectrodactyly, with or without cleft lip and palate, and variable additional features. All the reported cases occurred sporadically. Although several causal genes of HPE and ectrodactyly have been identified, the genetic cause of Hartsfield syndrome remains unknown. We hypothesised that a single key developmental gene may underlie the co-occurrence of HPE and ectrodactyly.

Methods

We used whole exome sequencing in four isolated cases including one case-parents trio, and direct Sanger sequencing of three additional cases, to investigate the causative variants in Hartsfield syndrome.

Results

We identified a novel FGFR1 mutation in six out of seven patients. Affected residues are highly conserved and are located in the extracellular binding domain of the receptor (two homozygous mutations) or the intracellular tyrosine kinase domain (four heterozygous de novo variants). Strikingly, among the six novel mutations, three are located in close proximity to the ATP's phosphates or the coordinating magnesium, with one position required for kinase activity, and three are adjacent to known mutations involved in Kallmann syndrome plus other developmental anomalies.

Conclusions

Dominant or recessive FGFR1 mutations are responsible for Hartsfield syndrome, consistent with the known roles of FGFR1 in vertebrate ontogeny and conditional Fgfr1-deficient mice. Our study shows that, in humans, lack of accurate FGFR1 activation can disrupt both brain and hand/foot midline development, and that FGFR1 loss-of-function mutations are responsible for a wider spectrum of clinical anomalies than previously thought, ranging in severity from seemingly isolated hypogonadotropic hypogonadism, through Kallmann syndrome with or without additional features, to Hartsfield syndrome at its most severe end.

Variations in PROKR2, but not PROK2, are associated with hypopituitarism and septo-optic dysplasia

CONTEXT

Loss-of-function mutations in PROK2 and PROKR2 have been implicated in Kallmann syndrome (KS), characterized by hypogonadotropic hypogonadism and anosmia. Recent data suggest overlapping phenotypes/genotypes between KS and congenital hypopituitarism (CH), including septo-optic dysplasia (SOD).

OBJECTIVE

We screened a cohort of patients with complex forms of CH (n = 422) for mutations in PROK2 and PROKR2.

RESULTS

We detected 5 PROKR2 variants in 11 patients with SOD/CH: novel p.G371R and previously reported p.A51T, p.R85L, p.L173R, and p.R268C-the latter 3 being known functionally deleterious variants. Surprisingly, 1 patient with SOD was heterozygous for the p.L173R variant, whereas his phenotypically unaffected mother was homozygous for the variant. We sought to clarify the role of PROKR2 in hypothalamopituitary development through analysis of Prokr2(-/-) mice. Interestingly, these revealed predominantly normal hypothalamopituitary development and terminal cell differentiation, with the exception of reduced LH; this was inconsistent with patient phenotypes and more analogous to the healthy mother, although she did not have KS, unlike the Prokr2(-/-) mice.

CONCLUSIONS

The role of PROKR2 in the etiology of CH, SOD, and KS is uncertain, as demonstrated by no clear phenotype-genotype correlation; loss-of-function variants in heterozygosity or homozygosity can be associated with these disorders. However, we report a phenotypically normal parent, homozygous for p.L173R. Our data suggest that the variants identified herein are unlikely to be implicated in isolation in these disorders; other genetic or environmental modifiers may also impact on the etiology. Given the phenotypic variability, genetic counseling may presently be inappropriate.

Responsiveness to a physiological regimen of GnRH therapy and relation to genotype in women with isolated hypogonadotropic hypogonadism

CONTEXT

Isolated hypogonadotropic hypogonadism (IHH) is caused by defective GnRH secretion or action resulting in absent or incomplete pubertal development and infertility. Most women with IHH ovulate with physiological GnRH replacement, implicating GnRH deficiency as the etiology. However, a subset does not respond normally, suggesting the presence of defects at the pituitary or ovary.

OBJECTIVES

The objective of the study was to unmask pituitary or ovarian defects in IHH women using a physiological regimen of GnRH replacement, relating these responses to genes known to cause IHH.

DESIGN, SETTING, AND SUBJECTS

This study is a retrospective analysis of 37 IHH women treated with iv pulsatile GnRH (75 ng/kg per bolus).

MAIN OUTCOME MEASURES

Serum gonadotropin and sex steroid levels were measured, and 14 genes implicated in IHH were sequenced.

RESULTS

During their first cycle of GnRH replacement, normal cycles were recreated in 60% (22 of 37) of IHH women. Thirty percent of women (12 of 37) demonstrated an attenuated gonadotropin response, indicating pituitary resistance, and 10% (3 of 37) exhibited an exaggerated FSH response, consistent with ovarian resistance. Mutations in CHD7, FGFR1, KAL1, TAC3, and TACR3 were documented in IHH women with normal cycles, whereas mutations were identified in GNRHR, PROKR2, and FGFR1 in those with pituitary resistance. Women with ovarian resistance were mutation negative.

CONCLUSIONS

Although physiological replacement with GnRH recreates normal menstrual cycle dynamics in most IHH women, hypogonadotropic responses in the first week of treatment identify a subset of women with pituitary dysfunction, only some of whom have mutations in GNRHR. IHH women with hypergonadotropic responses to GnRH replacement, consistent with an additional ovarian defect, did not have mutations in genes known to cause IHH, similar to our findings in a subset of IHH men with evidence of an additional testicular defect.

Optic nerve hypoplasia syndrome: a review of the epidemiology and clinical associations

OPINION STATEMENT

BACKGROUND

Optic nerve hypoplasia (ONH) has developed into a leading cause of congenital blindness. The frequently associated features of hypopituitarism and absent septum pellucidum were felt to have embryonic linkage as "septo-optic dysplasia" or "de Morsier's syndrome." More recent studies have suggested these associations are independent of one another. This review provides an assessment of the historical and recent evidence linking neuroradiologic, endocrinologic and developmental morbidity in patients with ONH. The prenatal risk factors, heritability, and genetic mutations associated with ONH are described.

RESULTS

Recognition of the critical association of ONH with hypopituitarism should be attributed to William Hoyt, not Georges de Morsier. De Morsier never described a case of ONH or recognized its association with hypopituitarism or missing septum pellucidum. Hypopituitarism is caused by hypothalamic dysfunction. This, and other more recently identified associations with ONH, such as developmental delay and autism, are independent of septum pellucidum development. Other common neuroradiographic associations such as corpus callosum hypoplasia, gyrus dysplasia, and cortical heterotopia may have prognostic significance. The predominant prenatal risk factors for ONH are primiparity and young maternal age. Presumed risk factors such as prenatal exposure to drugs and alcohol are not supported by scrutiny of the literature. Heritability and identified gene mutations in cases of ONH are rare.

CONCLUSION

Children with ONH require monitoring for many systemic, developmental, and even life-threatening problems independent of the severity of ONH and presence of brain malformations including abnormalities of the septum pellucidum. "Septo-optic dysplasia" and "de Morsier's syndrome" are historically inaccurate and clinically misleading terms.

Submicroscopic deletion involving the fibroblast growth factor receptor 1 gene in a patient with combined pituitary hormone deficiency

Combined pituitary hormone deficiency (CPHD), isolated hypogonadotropic hypogonadism (IHH), Kallmann syndrome (KS), and septo-optic dysplasia (SOD) are genetically related conditions caused by abnormal development of the anterior midline in the forebrain. Although mutations in the fibroblast growth factor receptor 1 (FGFR1) gene have been implicated in the development of IHH, KS, and SOD, the relevance of FGFR1 abnormalities to CPHD remains to be elucidated. Here, we report a Japanese female patient with CPHD and FGFR1 haploinsufficiency. The patient was identified through copy-number analyses and direct sequencing of FGFR1 performed for 69 patients with CPHD. The patient presented with a combined deficiency of GH, LH and FSH, and multiple neurological abnormalities. In addition, normal TSH values along with a low free T4 level indicated the presence of central hypothyroidism. Molecular analyses identified a heterozygous ~ 8.5 Mb deletion involving 56 genes and pseudogenes. None of these genes except FGFR1 have been associated with brain development. No FGFR1 abnormalities were identified in the remaining 68 patients, although two patients carried nucleotide substitutions (p.V102I and p.S107L) that were assessed as benign polymorphism by in vitro functional assays. These results indicate a possible role of FGFR1 in anterior pituitary function and the rarity of FGFR1 abnormalities in patients with CPHD.

Isolated central hypothyroidism in young siblings as a manifestation of PROP1 deficiency: clinical impact of whole exome sequencing

BACKGROUND/AIMS

Central hypothyroidism (CH) in children is rare and may be due to a variety of genetic defects. Most of these defects, but not all, are associated with additional pituitary hormone deficits. In a young child presenting with CH, it is important to determine whether additional pituitary hormone deficiencies are present, but this may be difficult to establish clinically.

METHODS

We describe the clinical characteristics of two young siblings, aged 6 months and 2 years, presenting with isolated CH. Whole exome sequencing was performed to determine the genetic basis of isolated CH.

RESULTS

A homozygous frameshift mutation of PROP1 (296delGA) was identified in both probands. Defects in PROP1 cause progressive deficiency of multiple pituitary hormones. Based on this genetic diagnosis, further clinical testing was performed that demonstrated growth hormone deficiency in one sibling.

CONCLUSIONS

PROP1 deficiency may present as isolated CH at a very young age. In disorders with multiple potential causative genes, whole exome sequencing may facilitate rapid genetic diagnosis and lead to important changes in clinical management.

PROKR2 and PROK2 mutations cause isolated congenital anosmia without gonadotropic deficiency

OBJECTIVE

Isolated congenital anosmia (ICA) is a rare phenotype defined as absent recall of any olfactory sensations since birth and the absence of any disease known to cause anosmia. Although most cases of ICA are sporadic, reports of familial cases suggest a genetic cause. ICA due to olfactory bulb agenesis and associated to hypogonadotropic hypogonadism defines Kallmann syndrome (KS), in which several gene defects have been described. In KS families, the phenotype may be restricted to ICA. We therefore hypothesized that mutations in KS genes cause ICA in patients, even in the absence of family history of reproduction disorders.

DESIGN AND METHODS

In 25 patients with ICA and olfactory bulb agenesis, a detailed phenotype analysis was conducted and the coding sequences of KAL1, FGFR1, FGF8, PROKR2, and PROK2 were sequenced.

RESULTS

Three PROKR2 mutations previously described in KS and one new PROK2 mutation were found. Investigation of the families showed incomplete penetrance of these mutations.

CONCLUSIONS

This study is the first to report genetic causes of ICA and indicates that KS genes must be screened in patients with ICA. It also confirms the considerable complexity of GNRH neuron development in humans.

PROK2/PROKR2 Signaling and Kallmann Syndrome

Kallmann syndrome (KS) is a developmental disease that associates hypogonadism and a deficiency of the sense of smell. The reproductive phenotype of KS results from the primary interruption of the olfactory, vomeronasal, and terminal nerve fibers in the frontonasal region, which in turn disrupts the embryonic migration of neuroendocrine gonadotropin-releasing hormone (GnRH) synthesizing cells from the nose to the brain. This is a highly heterogeneous genetic disease, and mutations in any of the nine genes identified so far have been found in approximately 30% of the KS patients. PROKR2 and PROK2, which encode the G protein-coupled prokineticin receptor-2 and its ligand prokineticin-2, respectively, are two of these genes. Homozygous knockout mice for the orthologous genes exhibit a phenotype reminiscent of the KS features, but biallelic mutations in PROKR2 or PROK2 (autosomal recessive mode of disease transmission) have been found only in a minority of the patients, whereas most patients carrying mutations in these genes are heterozygotes. The mutations, mainly missense mutations, have deleterious effects on PROKR2 signaling in transfected cells, ranging from defective cell surface-targeting of the receptor to defective coupling to G proteins or impaired receptor-ligand interaction, but the same mutations have also been found in apparently unaffected individuals, which suggests a digenic/oligogenic mode of inheritance of the disease in heterozygous patients. This non-Mendelian mode of inheritance has so far been confirmed only in a few patients. However, it may account for the unusually high proportion of KS sporadic cases compared to familial cases.

Evidence of the importance of the first intracellular loop of prokineticin receptor 2 in receptor function

Prokineticin receptors (PROKR) are G protein-coupled receptors (GPCR) that regulate diverse biological processes, including olfactory bulb neurogenesis and GnRH neuronal migration. Mutations in PROKR2 have been described in patients with varying degrees of GnRH deficiency and are located in diverse functional domains of the receptor. Our goal was to determine whether variants in the first intracellular loop (ICL1) of PROKR2 (R80C, R85C, and R85H) identified in patients with hypogonadotropic hypogonadism interfere with receptor function and to elucidate the mechanisms of these effects. Because of structural homology among GPCR, clarification of the role of ICL1 in PROKR2 activity may contribute to a better understanding of this domain across other GPCR. The effects of the ICL1 PROKR2 mutations on activation of signal transduction pathways, ligand binding, and receptor expression were evaluated. Our results indicated that the R85C and R85H PROKR2 mutations interfere only modestly with receptor function, whereas the R80C PROKR2 mutation leads to a marked reduction in receptor activity. Cotransfection of wild-type (WT) and R80C PROKR2 showed that the R80C mutant could exert a dominant negative effect on WT PROKR2 in vitro by interfering with WT receptor expression. In summary, we have shown the importance of Arg80 in ICL1 for PROKR2 expression and demonstrate that R80C PROKR2 exerts a dominant negative effect on WT PROKR2.