A novel dysfunctional LHX4 mutation with high phenotypical variability in patients with hypopituitarism

Re-analysis of gene mutations found in pituitary stalk interruption syndrome and a new hypothesis on the etiology

Background

Pituitary stalk interruption syndrome (PSIS) is a complex clinical syndrome characterized by varied pituitary hormone deficiencies, leading to severe manifestations across multiple systems. These include lifelong infertility, short stature, mental retardation, and potentially life-threatening pituitary crises if not promptly diagnosed and treated. Despite extensive research, the precise pathogenesis of PSIS remains unclear. Currently, there are two proposed theories regarding the pathogenic mechanisms: the genetic defect theory and the perinatal injury theory.

Methods

We systematically searched English databases (PubMed, Web of Science, Embase) and Chinese databases (CNKI, WanFang Med Online, Sinomed) up to February 24, 2023, to summarize studies on gene sequencing in PSIS patients. Enrichment analyses of reported mutated genes were subsequently performed using the Metascape platform.

Results

Our study included 37 articles. KEGG enrichment analysis revealed mutated genes were enriched in the Notch signaling pathway, Wnt signaling pathway, and Hedgehog signaling pathway. GO enrichment analysis demonstrated mutated genes were enriched in biological processes such as embryonic development, brain development, axon development and guidance, and development of other organs.

Conclusion

Based on our summary and analyses, we propose a new hypothesis: disruptions in normal embryonic development, partially stemming from the genetic background and/or specific gene mutations in individuals, may increase the likelihood of abnormal fetal deliveries, where different degrees of traction during delivery may lead to different levels of pituitary stalk interruption and posterior lobe ectopia. The clinical diversity observed in PSIS patients may result from a combination of genetic background, specific mutations, and variable degrees of traction during delivery.

Exome sequencing in 16 patients with pituitary stalk interruption syndrome: A monocentric study

Pituitary stalk interruption syndrome (PSIS) is a rare disorder characterized by an absent or ectopic posterior pituitary, absent or interrupted pituitary stalk and anterior pituitary hypoplasia on magnetic resonance imaging (MRI), as well in some cases a range of heterogeneous somatic anomalies. The triad can be incomplete. Here, we performed exome sequencing on 16 sporadic patients, aged 0.4 to 13.7 years diagnosed with isolated or complex PSIS. Growth hormone deficiency was isolated in 10 cases, or associated with thyrotropin deficiency in 6 others (isolated (2 cases), associated with adrenocorticotropin deficiency (1 case), gonadotropins deficiency (1 case), or multiple deficiencies (2 cases)). Additional phenotypic anomalies were present in six cases (37.5%) including four with ophthalmic disorders. In 13 patients variants were identified that may contribute to the phenotype. However, only a single individual carried a variant classified as pathogenic. This child presented with the typical clinical presentation of Okur-Chung neurodevelopmental syndrome due to a CSNK2A1 missense variant. We also identified variants in the holoprosencephaly associated genes GLI2 and PTCH1. A likely pathogenic novel splice site variant in the GLI2 gene was observed in a child with PSIS and megacisterna magna. In the remaining 11 cases 26 variants in genes associated with pituitary development or function were identified and were classified of unknown significance. Compared with syndromic forms the diagnostic yield in the isolated forms of PSIS is low. Although we identified rare or novel missense variants in several hypogonadotropic hypogonadism genes (e.g. FGF17, HS6ST1, KISS1R, CHD7, IL17RD) definitively linking them to the PSIS phenotype is premature. A major challenge remains to identify pathogenic variants in cases with isolated PSIS.

Whole-Exome Sequencing Identified Rare Genetic Variants Associated with Undervirilized Genitalia in Taiwanese Pediatric Patients

Disorders/differences of sex development (DSDs) are a group of rare and phenotypically variable diseases. The underlying genetic causes of most cases of 46XY DSDs remains unknown. Despite the advent of genetic testing, current investigations of the causes of DSDs allow genetic-mechanism identification in about 20-35% of cases. This study aimed primarily to establish a rapid and high-throughput genetic test for undervirilized males with and without additional dysmorphic features. Routine chromosomal and endocrinological investigations were performed as part of DSD evaluation. We applied whole-exome sequencing (WES) complemented with multiplex ligation-dependent probe amplification to seek explainable genetic causes. Integrated computing programs were used to call and predict the functions of genetic variants. We recruited 20 patients and identified the genetic etiologies for 14 (70%) patients. A total of seven of the patients who presented isolated DSD phenotypes were found to have causative variants in the AR, MAP3K1, and FLNA genes. Moreover, the other seven patients presented additional phenotypes beyond undervirilized genitalia. Among them, two patients were compatible with CHARGE syndrome, one with Robinow syndrome, and another three with hypogonadotropic hypogonadism. One patient, who carried a heterozygous FLNA mutation, also harbored a heterozygous PTPN11 mutation and thus presented some phenotypes of Noonan syndrome. We identified several genetic variants (12 nonsense mutations and one microdeletion) that account for syndromic and nonsyndromic DSDs in the Taiwanese population. The identification of these causative genes extended our current understanding of sex development and related congenital disorders.

Novel gross deletion at the LHX4 gene locus in a child with growth hormone deficiency

OBJECTIVE

To identify and characterize a novel deletion at the LHX4 gene locus in a proband with growth hormone deficiency (GHD).

METHODS

Long range polymerase chain reaction (PCR) amplification was used to confirm the suspected deletion and to identify the rough locations of the end points. Sanger sequencing was carried out to identify the exact end points of the deletion.

RESULTS

Suspected deletion was confirmed via long range PCR amplification. Sanger sequencing identified the end points of the deletion within three nucleotide repeat sequences ("CTT"). The total length of the deleted segment was 12 127 base pairs and it includes complete exon 5 and exon 6 of the LHX4 gene. Therefore the homeodomain motif coded by exons 4 and 5, might be affected.

CONCLUSION

We have identified a novel deletion that spans exon 5 and exon 6 of the LHX4 gene that could have occurred via microhomology mediated non-recurrent rearrangement. The deletion characterized does not appear to have been reported before. To our knowledge this novel deletion is the first identified LHX4 variant from Sri Lanka and it explains the phenotype of the proband characterized by growth hormone deficiency, hypoplastic anterior pituitary and subsequent deficiency of thyroid stimulating hormone and adrenocorticotropic hormone (ACTH).

Advances in differential diagnosis and management of growth hormone deficiency in children

Growth hormone (GH) deficiency (GHD) in children is defined as impaired production of GH by the pituitary gland that results in growth failure. This disease might be congenital or acquired, and occurs in isolation or in the setting of multiple pituitary hormone deficiency. Isolated GHD has an estimated prevalence of 1 patient per 4000-10,000 live births and can be due to multiple causes, some of which are yet to be determined. Establishing the correct diagnosis remains key in children with short stature, as initiating treatment with recombinant human GH can help them attain their genetically determined adult height. During the past two decades, our understanding of the benefits of continuing GH therapy throughout the transition period from childhood to adulthood has increased. Improvements in transitional care will help alleviate the consequent physical and psychological problems that can arise from adult GHD, although the consequences of a lack of hormone replacement are less severe in adults than in children. In this Review, we discuss the differential diagnosis in children with GHD, including details of clinical presentation, neuroimaging and genetic testing. Furthermore, we highlight advances and issues in the management of GHD, including details of transitional care.

Comprehensive Identification of Pathogenic Gene Variants in Patients With Neuroendocrine Disorders

PURPOSE

Congenital hypopituitarism (CH) can present in isolation or with other birth defects. Mutations in multiple genes can cause CH, and the use of a genetic screening panel could establish the prevalence of mutations in known and candidate genes for this disorder. It could also increase the proportion of patients that receive a genetic diagnosis.

METHODS

We conducted target panel genetic screening using single-molecule molecular inversion probes sequencing to assess the frequency of mutations in known hypopituitarism genes and new candidates in Argentina. We captured genomic deoxyribonucleic acid from 170 pediatric patients with CH, either alone or with other abnormalities. We performed promoter activation assays to test the functional effects of patient variants in LHX3 and LHX4.

RESULTS

We found variants classified as pathogenic, likely pathogenic, or with uncertain significance in 15.3% of cases. These variants were identified in known CH causative genes (LHX3, LHX4, GLI2, OTX2, HESX1), in less frequently reported genes (FOXA2, BMP4, FGFR1, PROKR2, PNPLA6) and in new candidate genes (BMP2, HMGA2, HNF1A, NKX2-1).

CONCLUSION

In this work, we report the prevalence of mutations in known CH genes in Argentina and provide evidence for new candidate genes. We show that CH is a genetically heterogeneous disease with high phenotypic variation and incomplete penetrance, and our results support the need for further gene discovery for CH. Identifying population-specific pathogenic variants will improve the capacity of genetic data to predict eventual clinical outcomes.

Clinical lessons learned in constitutional hypopituitarism from two decades of experience in a large international cohort

CONTEXT

The international GENHYPOPIT network collects phenotypical data and screens genetic causes of non-acquired hypopituitarism.

AIMS

To describe main phenotype patterns and their evolution through life.

DESIGN

Patients were screened according to their phenotype for coding sequence variations in 8 genes: HESX1, LHX3, LHX4, PROP1, POU1F1, TBX19, OTX2 and PROKR2.

RESULTS

Among 1213 patients (1143 index cases), the age of diagnosis of hypopituitarism was congenital (24%), in childhood (28%), at puberty (32%), in adulthood (7.2%) or not available (8.8%). Noteworthy, pituitary hormonal deficiencies kept on evolving during adulthood in 49 of patients. Growth Hormone deficiency (GHD) affected 85.8% of patients and was often the first diagnosed deficiency. AdrenoCorticoTropic Hormone deficiency rarely preceded GHD, but usually followed it by over 10 years. Pituitary Magnetic Resonance Imaging (MRI) abnormalities were common (79.7%), with 39.4% pituitary stalk interruption syndrome (PSIS). The most frequently associated extrapituitary malformations were ophthalmological abnormalities (16.1%). Prevalence of identified mutations was 7.3% of index cases (84/1143) and 29.5% in familial cases (n = 146). Genetic analysis in 449 patients without extrapituitary phenotype revealed 36 PROP1, 2 POU1F1 and 17 TBX19 mutations.

CONCLUSION

This large international cohort highlights atypical phenotypic presentation of constitutional hypopituitarism, such as post pubertal presentation or adult progression of hormonal deficiencies. These results justify long-term follow-up, and the need for systematic evaluation of associated abnormalities. Genetic defects were rarely identified, mainly PROP1 mutations in pure endocrine phenotypes.

Pituitary stalk interruption syndrome

Pituitary stalk interruption syndrome (PSIS) is a distinct developmental defect of the pituitary gland identified by magnetic resonance imaging and characterized by a thin, interrupted, attenuated or absent pituitary stalk, hypoplasia or aplasia of the adenohypophysis, and an ectopic posterior pituitary. The precise etiology of PSIS still remains elusive or incompletely confirmed in most cases. Adverse perinatal events, including breech delivery and hypoxia, were initially proposed as the underlying mechanism affecting the hypothalamic-pituitary axis. Nevertheless, recent findings have uncovered a wide variety of PSIS-associated molecular defects in genes involved in pituitary development, holoprosencephaly (HPE), neural development, and other important cellular processes such as cilia function. The application of whole exome sequencing (WES) in relatively large cohorts has identified an expanded pool of potential candidate genes, mostly related to the Wnt, Notch, and sonic hedgehog signaling pathways that regulate pituitary growth and development during embryogenesis. Importantly, WES has revealed coexisting pathogenic variants in a significant number of patients; therefore, pointing to a multigenic origin and inheritance pattern of PSIS. The disorder is characterized by inter- and intrafamilial variability and incomplete or variable penetrance. Overall, PSIS is currently viewed as a mild form of an expanded HPE spectrum. The wide and complex clinical manifestations include evolving pituitary hormone deficiencies (with variable timing of onset and progression) and extrapituitary malformations. Severe and life-threatening symptomatology is observed in a subset of patients with complete pituitary hormone deficiency during the neonatal period. Nevertheless, most patients are referred later in childhood for growth retardation. Prompt and appropriate hormone substitution therapy constitutes the cornerstone of treatment. Further studies are needed to uncover the etiopathogenesis of PSIS.

Pituitary stalk interruption syndrome is characterized by genetic heterogeneity

Pituitary stalk interruption syndrome is a rare disorder characterized by an absent or ectopic posterior pituitary, interrupted pituitary stalk and anterior pituitary hypoplasia, as well as in some cases, a range of heterogeneous somatic anomalies. A genetic cause is identified in only around 5% of all cases. Here, we define the genetic variants associated with PSIS followed by the same pediatric endocrinologist. Exome sequencing was performed in 52 (33 boys and 19 girls), including 2 familial cases single center pediatric cases, among them associated 36 (69.2%) had associated symptoms or syndromes. We identified rare and novel variants in genes (37 families with 39 individuals) known to be involved in one or more of the following-midline development and/or pituitary development or function (BMP4, CDON, GLI2, GLI3, HESX1, KIAA0556, LHX9, NKX2-1, PROP1, PTCH1, SHH, TBX19, TGIF1), syndromic and non-syndromic forms of hypogonadotropic hypogonadism (CCDC141, CHD7, FANCA, FANCC, FANCD2, FANCE, FANCG, IL17RD, KISS1R, NSMF, PMM2, SEMA3E, WDR11), syndromic forms of short stature (FGFR3, NBAS, PRMT7, RAF1, SLX4, SMARCA2, SOX11), cerebellum atrophy with optic anomalies (DNMT1, NBAS), axonal migration (ROBO1, SLIT2), and agenesis of the corpus callosum (ARID1B, CC2D2A, CEP120, CSPP1, DHCR7, INPP5E, VPS13B, ZNF423). Pituitary stalk interruption syndrome is characterized by a complex genetic heterogeneity, that reflects a complex phenotypic heterogeneity. Seizures, intellectual disability, micropenis or cryptorchidism, seen at presentation are usually considered as secondary to the pituitary deficiencies. However, this study shows that they are due to specific gene mutations. PSIS should therefore be considered as part of the phenotypic spectrum of other known genetic syndromes rather than as specific clinical entity.

Pituitary stalk interruption syndrome and liver changes: From clinical features to mechanisms

Pituitary stalk interruption syndrome (PSIS) is a rare congenital abnormality characterized by thinning or disappearance of the pituitary stalk, hypoplasia of the anterior pituitary and an ectopic posterior pituitary. Although the etiology of PSIS is still unclear, gene changes and perinatal adverse events such as breech delivery may play important roles in the pathogenesis of PSIS. PSIS can cause multiple hormone deficiencies, such as growth hormone, which then cause a series of changes in the human body. On the one hand, hormone changes affect growth and development, and on the other hand, they could affect human metabolism and subsequently the liver resulting in nonalcoholic fatty liver disease (NAFLD). Under the synergistic effect of multiple mechanisms, the progression of NAFLD caused by PSIS is faster than that due to other causes. Therefore, in addition to early identification of PSIS, timely hormone replacement therapy and monitoring of relevant hormone levels, clinicians should routinely assess the liver function while managing PSIS.

Copy Number Variants Contributing to Combined Pituitary Hormone Deficiency

Combined pituitary hormone deficiency represents a disorder with complex etiology. For many patients, causes of the disease remain unexplained, despite usage of advanced genetic testing. Although major and common transcription factors were identified two decades ago, we still struggle with identification of rare inborn factors contributing to pituitary function. In this report, we follow up genomic screening of CPHD patient cohort that were previously tested for changes in a coding sequences of genes with the use of the whole exome. We aimed to find contribution of rare copy number variations (CNVs). As a result, we identified genomic imbalances in 7 regions among 12 CPHD patients. Five out of seven regions showed copy gains whereas two presented losses of genomic fragment. Three regions with detected gains encompassed known CPHD genes namely LHX4, HESX1, and OTX2. Among new CPHD loci, the most interesting seem to be the region covering SIX3 gene, that is abundantly expressed in developing brain, and together with HESX1 contributes to pituitary organogenesis as it was evidenced before in functional studies. In conclusion, with the use of broadened genomic approach we identified copy number imbalances for 12 CPHD patients. Although further functional studies are required in order to estimate its true impact on expression pattern during pituitary organogenesis and CPHD etiology.

Genetic causes of hypopituitarism

Hypopituitarism in neonates is rare, but has life-threatening complications if untreated. This review describes the features of hypopituitarism and the evidence for which infants in whom a genetic cause should be suspected. Importantly, neonates are often asymptomatic or present with non-specific symptoms. Hypopituitarism can be due to abnormal gland development as a result of genetic defects, which result from mutations in gene coding for transcription factors which regulate pituitary development. The mutations can be divided into those causing isolated hypopituitarism or those causing syndromes with associated hypopituitarism. The latter involve mutations in transcription factors which regulate pituitary, as well as extra-pituitary development. There is a paucity of evidence as to which patients should be investigated for genetic mutations, but detailed clinical and biochemical phenotyping with magnetic resonance imaging of the pituitary gland could help target those in whom genetic investigations would be most appropriate.

Congenital Hypopituitarism During the Neonatal Period: Epidemiology, Pathogenesis, Therapeutic Options, and Outcome

Introduction: Congenital hypopituitarism (CH) is characterized by a deficiency of one or more pituitary hormones. The pituitary gland is a central regulator of growth, metabolism, and reproduction. The anterior pituitary produces and secretes growth hormone (GH), adrenocorticotropic hormone, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. The posterior pituitary hormone secretes antidiuretic hormone and oxytocin. Epidemiology: The incidence is 1 in 4,000-1 in 10,000. The majority of CH cases are sporadic; however, a small number of familial cases have been identified. In the latter, a molecular basis has frequently been identified. Between 80-90% of CH cases remain unsolved in terms of molecular genetics. Pathogenesis: Several transcription factors and signaling molecules are involved in the development of the pituitary gland. Mutations in any of these genes may result in CH including HESX1, PROP1, POU1F1, LHX3, LHX4, SOX2, SOX3, OTX2, PAX6, FGFR1, GLI2, and FGF8. Over the last 5 years, several novel genes have been identified in association with CH, but it is likely that many genes remain to be identified, as the majority of patients with CH do not have an identified mutation. Clinical manifestations: Genotype-phenotype correlations are difficult to establish. There is a high phenotypic variability associated with different genetic mutations. The clinical spectrum includes severe midline developmental disorders, hypopituitarism (in isolation or combined with other congenital abnormalities), and isolated hormone deficiencies. Diagnosis and treatment: Key investigations include MRI and baseline and dynamic pituitary function tests. However, dynamic tests of GH secretion cannot be performed in the neonatal period, and a diagnosis of GH deficiency may be based on auxology, MRI findings, and low growth factor concentrations. Once a hormone deficit is confirmed, hormone replacement should be started. If onset is acute with hypoglycaemia, cortisol deficiency should be excluded, and if identified this should be rapidly treated, as should TSH deficiency. This review aims to give an overview of CH including management of this complex condition.

Generation and characterization of Lhx4tdT reporter knock-in and Lhx4loxP conditional knockout mice

LHX4 is a LIM-homeodomain transcription factor essential for the development of spinal cord and pituitary gland. Mice with homozygous Lhx4-null mutation suffer early postnatal death from lung defect. In this study, to facilitate the research on Lhx4 function, we designed a targeting construct to generate two novel Lhx4 mouse lines: Lhx4 loxP conditional knockout and Lhx4 tdT reporter knock-in mice. Lhx4 tdT/+ , Lhx4 loxP/+ , and Lhx4 loxP/loxP were viable, fertile, and did not display any gross abnormalities. By breeding Lhx4 loxP line with Cre-expressing mice, the Exon 3 of Lhx4 was efficiently removed, resulting in a shift in the reading frame and the inactivation of Lhx4. The expression of tdTomato knock-in reporter recapitulated the endogenous LHX4 expression and was detected in the retina, spinal cord, pituitary gland, and hindbrain of Lhx4 tdT mice. Thus, Lhx4 tdT and Lhx4 loxP mouse lines provide valuable tools for unraveling the tissue-specific role of Lhx4 at postnatal stages in mice.

Pituitary Transcription Factor Mutations Leading to Hypopituitarism

Congenital pituitary hormone deficiency is a disabling condition. It is part of a spectrum of disorders including craniofacial midline developmental defects ranging from holoprosencephaly through septo-optic dysplasia to combined and isolated pituitary hormone deficiency. The first genes discovered in the human disease were based on mouse models of dwarfism due to mutations in transcription factor genes. High-throughput DNA sequencing technologies enabled clinicians and researchers to find novel genetic causes of hypopituitarism for the more than three quarters of patients without a known genetic diagnosis to date. Transcription factor (TF) genes are at the forefront of the functional analysis of novel variants of unknown significance due to the relative ease in in vitro testing in a research lab. Genetic testing in hypopituitarism is of high importance to the individual and their family to predict phenotype composition, disease progression and to avoid life-threatening complications such as secondary adrenal insufficiency.This chapter aims to highlight our current understanding about (1) the contribution of TF genes to pituitary development (2) the diversity of inheritance and phenotype features in combined and select isolated pituitary hormone deficiency and (3) provide an initial assessment on how to approach variants of unknown significance in human hypopituitarism. Our better understanding on how transcription factor gene variants lead to hypopituitarism is a meaningful step to plan advanced therapies to specific genetic changes in the future.

Heterozygous LHX3 mutations may lead to a mild phenotype of combined pituitary hormone deficiency

LHX3 is an LIM domain transcription factor involved in the early steps of pituitary ontogenesis. We report here functional studies of three allelic variants, including the first heterozygous variant of LHX3 NM_178138.5(LHX3):c.587T>C (p.(Leu196Pro)) that may be responsible for a milder phenotype of hypopituitarism. Our functional studies showed that NM_178138.5(LHX3):c.587T>C (p.(Leu196Pro)) was not able to activate target promoters in vitro, as it did not bind DNA, and likely affected LHX3 function via a mechanism of haplo-insufficiency. Our study demonstrates the possibility that patients with a heterozygous variant of LHX3 may have pituitary deficiencies, with a milder phenotype than patients with homozygous variants. It is thus of vital to propose an optimal follow-up of such patients, who, until now, were considered as not being at risk of presenting pituitary deficiency. The second variant NM_178138.5(LHX3):c.622C>G (p.(Arg208Gly)), present in a homozygous state, displayed decreased transactivating ability without loss of binding capacity in vitro, concordant with in silico analysis; it should thus be considered to affect LHX3 function. In contrast, the NM_178138.5(LHX3):c.929G>C (p.(Arg310Pro)) variant, in a heterozygous state, also predicted as deleterious in silico, proved functionally active in vitro, and should thus still be classified as a variant of unknown significance. Our study emphasizes the need for functional studies due to the limits of software-based predictions of new variants, and the possible association of a pituitary phenotype to heterozygous LHX3 variants.

Mutations in the Human ROBO1 Gene in Pituitary Stalk Interruption Syndrome

Context

Pituitary stalk interruption syndrome (PSIS) is characterized by a thin or absent pituitary stalk usually in association with an ectopic posterior pituitary and hypoplasia/aplasia of the anterior pituitary. Associated phenotypes include varied ocular anomalies, hypoglycemia, micropenis/cryptorchidism, growth failure, or combined pituitary hormone deficiencies. Although genetic causes have been identified, they explain only around 5% of PSIS cases.

Objective

To identify genetic causes of PSIS by exome sequencing.

Design

Exon enrichment was performed using the Agilent SureSelect Human All Exon V4. Paired-end sequencing was performed on the Illumina HiSeq2000 platform with an average sequencing coverage of ×50.

Patients

Patients with unexplained PSIS were included in the study.

Results

In five cases of unexplained PSIS including two familial cases, we identified a novel heterozygous frameshift and nonsense and missense mutations in the ROBO1 gene (p.Ala977Glnfs*40, two affected sibs; p.Tyr1114Ter, sporadic case, and p.Cys240Ser, affected child and paternal aunt) that controls embryonic axon guidance, and branching in the nervous system. Interestingly, four of the five cases of PSIS also presented with ocular anomalies, including hypermetropia with strabismus as well as ptosis.

Conclusions

These data suggest that mutations in ROBO1 contribute to PSIS and associated ocular anomalies.

Pituitary Hypoplasia

This article summarizes pituitary development and function as well as specific mutations of genes encoding the following transcription factors: HESX1, LHX3, LHX4, POU1F1, PROP1, and OTX2. Although several additional genetic defects related to hypopituitarism have been identified, this article focuses on these selected factors, as they have been well described in the literature in terms of clinical characterization of affected patients and molecular mechanisms of action, and therefore, are very relevant to clinical practice.

Contribution of LHX4 Mutations to Pituitary Deficits in a Cohort of 417 Unrelated Patients

CONTEXT

LHX4 encodes a LIM-homeodomain transcription factor that is implicated in early pituitary development. In humans, only 13 heterozygous LHX4 mutations have been associated with congenital hypopituitarism.

OBJECTIVE

The aims of this study were to evaluate the prevalence of LHX4 mutations in patients with hypopituitarism, to define the associated phenotypes, and to characterize the functional impact of the identified variants and the respective role of the 2 LIM domains of LHX4.

DESIGN AND PATIENTS

We screened 417 unrelated patients with isolated growth hormone deficiency or combined pituitary hormone deficiency associated with ectopic posterior pituitary and/or sella turcica anomalies for LHX4 mutations (Sanger sequencing). In vitro studies were performed to assess the functional consequences of the identified variants.

RESULTS

We identified 7 heterozygous variations, including p.(Tyr131*), p.(Arg48Thrfs*104), c.606+1G>T, p.Arg65Val, p.Thr163Pro, p.Arg221Gln, and p.Arg235Gln), that were associated with variable expressivity; 5 of the 7 were also associated with incomplete penetrance. The p.(Tyr131*), p.(Arg48Thrfs*104), p.Ala65Val, p.Thr163Pro, and p.Arg221Gln LHX4 variants are unable to transactivate the POU1F1 and GH promoters. As suggested by transactivation, subcellular localization, and protein-protein interaction studies, p.Arg235Gln is probably a rare polymorphism. Coimmunoprecipitation studies identified LHX3 as a potential protein partner of LHX4. As revealed by functional studies of LIM-defective recombinant LHX4 proteins, the LIM1 and LIM2 domains are not redundant.

CONCLUSION

This study, performed in the largest cohort of patients screened so far for LHX4 mutations, describes 6 disease-causing mutations that are responsible for congenital hypopituitarism. LHX4 mutations were found to be associated with variable expressivity, and most of them with incomplete penetrance; their contribution to pituitary deficits that are associated with an ectopic posterior pituitary and/or a sella turcica defect is ∼1.4% in the 417 probands tested.

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.

Hypopituitarism in the elderly: a narrative review on clinical management of hypothalamic-pituitary-gonadal, hypothalamic-pituitary-thyroid and hypothalamic-pituitary-adrenal axes dysfunction

Hypopituitarism is an uncommon and under-investigated endocrine disorder in old age since signs and symptoms are unspecific and, at least in part, can be attributed to the physiological effects of aging and related co-morbidities. Clinical presentation is often insidious being characterized by non-specific manifestations, such as weight gain, fatigue, low muscle strength, bradipsychism, hypotension or intolerance to cold. In these circumstances, hypopituitarism is a rarely life-threatening condition, but evolution may be more dramatic as a result of pituitary apoplexy, or when a serious condition of adrenal insufficiency suddenly occurs. Clinical presentation depends on the effects that each pituitary deficit can cause, and on their mutual relationship, but also, inevitably, it depends on the severity and duration of the deficit itself, as well as on the general condition of the patient. Indeed, indications and methods of hormone replacement therapy must include the need to normalize the endocrine profile without contributing to the worsening of intercurrent diseases, such as those of glucose and bone metabolism, and the cardiovascular system, or to the increasing cancer risk. Hormonal requirements of elderly patients are reduced compared to young adults, but a prompt diagnosis and appropriate treatment of pituitary deficiencies are strongly recommended, also in this age range.

Hypogonadotropic Hypogonadism in Infants with Congenital Hypopituitarism: A Challenge to Diagnose at an Early Stage

BACKGROUND

Combined pituitary hormone deficiency (CPHD) presents a wide spectrum of pituitary gland disorders. The postnatal gonadotropic surge provides a useful period to explore the gonadotropic axis for assessing the presence of congenital hypogonadotropic hypogonadism (CHH).

AIM

To explore the functioning of the hypothalamic-pituitary-gonadal axis in the postnatal gonadotropic surge for an early diagnosis of CHH in newborns or infants suspected of having CPHD.

SUBJECTS AND METHODS

A cohort of 27 boys under 6 months and 19 girls under 24 months of age with suspected hypopituitarism was studied. Serum concentrations of LH, FSH, testosterone, inhibin B, anti-Müllerian hormone (AMH) and estradiol were measured, and male external genitalia were characterized as normal or abnormal (micropenis, microorchidism and/or cryptorchidism).

RESULTS

CPHD was confirmed in 36 out of 46 patients. Low LH and testosterone levels were found in 66% of the hypopituitary males, in significant association with the presence of abnormal external genitalia. This abnormality had a positive predictive value of 93% for CHH. No significant association was observed between serum FSH, AMH and inhibin B and the patient's external genitalia.

CONCLUSION

In newborn or infant boys with CPHD, LH and testosterone concentrations measured throughout the postnatal gonadotropic surge, together with a detailed evaluation of the external genital phenotype, facilitate the diagnosis of CHH at an early stage.

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.

Recent advances in central congenital hypothyroidism

Central congenital hypothyroidism (CCH) may occur in isolation, or more frequently in combination with additional pituitary hormone deficits with or without associated extrapituitary abnormalities. Although uncommon, it may be more prevalent than previously thought, affecting up to 1:16 000 neonates in the Netherlands. Since TSH is not elevated, CCH will evade diagnosis in primary, TSH-based, CH screening programs and delayed detection may result in neurodevelopmental delay due to untreated neonatal hypothyroidism. Alternatively, coexisting growth hormones or ACTH deficiency may pose additional risks, such as life threatening hypoglycaemia. Genetic ascertainment is possible in a minority of cases and reveals mutations in genes controlling the TSH biosynthetic pathway (TSHB, TRHR, IGSF1) in isolated TSH deficiency, or early (HESX1, LHX3, LHX4, SOX3, OTX2) or late (PROP1, POU1F1) pituitary transcription factors in combined hormone deficits. Since TSH cannot be used as an indicator of euthyroidism, adequacy of treatment can be difficult to monitor due to a paucity of alternative biomarkers. This review will summarize the normal physiology of pituitary development and the hypothalamic-pituitary-thyroid axis, then describe known genetic causes of isolated central hypothyroidism and combined pituitary hormone deficits associated with TSH deficiency. Difficulties in diagnosis and management of these conditions will then be discussed.

Novel Lethal Form of Congenital Hypopituitarism Associated With the First Recessive LHX4 Mutation

BACKGROUND

LHX4 encodes a member of the LIM-homeodomain family of transcription factors that is required for normal development of the pituitary gland. To date, only incompletely penetrant heterozygous mutations in LHX4 have been described in patients with variable combined pituitary hormone deficiencies.

OBJECTIVE/HYPOTHESIS

To report a unique family with a novel recessive variant in LHX4 associated with a lethal form of congenital hypopituitarism that was identified through screening a total of 97 patients.

METHOD

We screened 97 unrelated patients with combined pituitary hormone deficiency, including 65% with an ectopic posterior pituitary, for variants in the LHX4 gene using Sanger sequencing. Control databases (1000 Genomes, dbSNP, Exome Variant Server, ExAC Browser) were consulted upon identification of variants.

RESULTS

We identified the first novel homozygous missense variant (c.377C>T, p.T126M) in two deceased male patients of Pakistani origin with severe panhypopituitarism associated with anterior pituitary aplasia and posterior pituitary ectopia. Both were born small for gestational age with a small phallus, undescended testes, and mid-facial hypoplasia. The parents' first-born child was a female with mid-facial hypoplasia (DNA was unavailable). Despite rapid commencement of hydrocortisone and T4 in the brothers, all three children died within the first week of life. The LHX4(p.T126M) variant is located within the LIM2 domain, in a highly conserved location. The absence of homozygosity for the variant in over 65 000 controls suggests that it is likely to be responsible for the phenotype.

CONCLUSION

We report, for the first time to our knowledge, a novel homozygous mutation in LHX4 associated with a lethal phenotype, implying that recessive mutations in LHX4 may be incompatible with life.

Identifying the Deleterious Effect of Rare LHX4 Allelic Variants, a Challenging Issue

LHX4 is a LIM homeodomain transcription factor involved in the early steps of pituitary ontogenesis. To date, 8 heterozygous LHX4 mutations have been reported as responsible of combined pituitary hormone deficiency (CPHD) in Humans. We identified 4 new LHX4 heterozygous allelic variants in patients with congenital hypopituitarism: W204X, delK242, N271S and Q346R. Our objective was to determine the role of LHX4 variants in patients’ phenotypes. Heterologous HEK293T cells were transfected with plasmids encoding for wild-type or mutant LHX4. Protein expression was analysed by Western Blot, and DNA binding by electro-mobility shift assay experiments. Target promoters of LHX4 were cotransfected with wild type or mutant LHX4 to test the transactivating abilities of each variant. Our results show that the W204X mutation was associated with early GH and TSH deficiencies and later onset ACTH deficiency. It led to a truncated protein unable to bind to alpha-Gsu promoter binding consensus sequence. W204X was not able to activate target promoters in vitro. Cotransfection experiments did not favour a dominant negative effect. In contrast, all other mutants were able to bind the promoters and led to an activation similar as that observed with wild type LHX4, suggesting that they were likely polymorphisms. To conclude, our study underlines the need for functional in vitro studies to ascertain the role of rare allelic variants of LHX4 in disease phenotypes. It supports the causative role of the W204X mutation in CPHD and adds up childhood onset ACTH deficiency to the clinical spectrum of the various phenotypes related to LHX4 mutations.

Lhx4 deficiency: increased cyclin-dependent kinase inhibitor expression and pituitary hypoplasia

Defects in the Lhx4, Lhx3, and Pitx2 genes can cause combined pituitary hormone deficiency and pituitary hypoplasia in both humans and mice. Not much is known about the mechanism underlying hypoplasia in these mutants beyond generally increased cell death and poorly maintained proliferation. We identified both common and unique abnormalities in developmental regulation of key cell cycle regulator gene expression in each of these three mutants. All three mutants exhibit reduced expression of the proliferative marker Ki67 and the transitional marker p57. We discovered that expression of the cyclin-dependent kinase inhibitor 1a (Cdkn1a or p21) is expanded dorsally in the pituitary primordium of both Lhx3 and Lhx4 mutants. Uniquely, Lhx4 mutants exhibit reduced cyclin D1 expression and have auxiliary pouch-like structures. We show evidence for indirect and direct effects of LHX4 on p21 expression in αT3-1 pituitary cells. In summary, Lhx4 is necessary for efficient pituitary progenitor cell proliferation and restriction of p21 expression.

Rare diseases in clinical endocrinology: a taxonomic classification system

PURPOSE

Rare endocrine-metabolic diseases (REMD) represent an important area in the field of medicine and pharmacology. The rare diseases of interest to endocrinologists involve all fields of endocrinology, including rare diseases of the pituitary, thyroid and adrenal glands, paraganglia, ovary and testis, disorders of bone and mineral metabolism, energy and lipid metabolism, water metabolism, and syndromes with possible involvement of multiple endocrine glands, and neuroendocrine tumors. Taking advantage of the constitution of a study group on REMD within the Italian Society of Endocrinology, consisting of basic and clinical scientists, a document on the taxonomy of REMD has been produced.

METHODS AND RESULTS

This document has been designed to include mainly REMD manifesting or persisting into adulthood. The taxonomy of REMD of the adult comprises a total of 166 main disorders, 338 including all variants and subtypes, described into 11 tables.

CONCLUSIONS

This report provides a complete taxonomy to classify REMD of the adult. In the future, the creation of registries of rare endocrine diseases to collect data on cohorts of patients and the development of common and standardized diagnostic and therapeutic pathways for each rare endocrine disease is advisable. This will help planning and performing intervention studies in larger groups of patients to prove the efficacy, effectiveness, and safety of a specific treatment.

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.

Pituitary stalk interruption syndrome in 58 Chinese patients: clinical features and genetic analysis

OBJECTIVES

Pituitary stalk interruption syndrome (PSIS) is rare and its clinical features and pathogenesis are poorly understood. This study characterized the clinical and genetic features of PSIS in Chinese patients.

DESIGN AND PATIENTS

Clinical data of 58 patients with PSIS and 46 patients with GH deficiency but a normal pituitary stalk (NPS) were retrospectively analysed. HESX1, LHX4, OTX2 and SOX3 polymorphisms were screened in 33 PSIS patients, and GH1 and GHRHR in 4 NPS patients.

RESULTS

Deficiency of GH was 100% in both PSIS and NPS groups. Other deficiency rates for PSIS and NPS groups were as follows: ACTH, 77·6% and 23·9%; TSH, 43·1% and 10·9%; LH/FSH, 94·2% and 47·4%; and combined pituitary hormone, 93·1% and 41·3% respectively. In PSIS and NPS patients, the percentages of anterior pituitary hypoplasia were 98·3% and 54·3%, pituitary stalk abnormality were 100% and 0%, and ectopic neurohypophysis were 91·4% and 0%. A novel heterozygous sequence variant (c.142A>T, p.T48S) was found in HESX1 in one PSIS patient, 3 polymorphisms (c.63T>C, p.G21G; c.450C>T, p.N150N; and c.983A>G, p.N328S) in LHX4 in 7, 1 and 31 PSIS patients, respectively, and a hemizygous polymorphism (c.157G>C, p.V53L) in SOX3 in one PSIS patient. No OTX2 abnormality was detected in PSIS patients, and no GH1 or GHRHR polymorphisms in NPS patients.

CONCLUSIONS

Compared with NPS, PSIS patients had more severe anterior pituitary hormone deficiency, lower anterior pituitary hormone secretion and higher probability of abnormal pituitary morphology. HESX1, LHX4 and SOX3 polymorphisms may be associated with PSIS.

Vertical transmission of hypopituitarism: critical importance of appropriate interpretation of thyroid function tests and levothyroxine therapy during pregnancy

BACKGROUND

Typically, newborns with congenital hypothyroidism are asymptomatic at birth, having been exposed to euthyroid mothers. However, hypopituitarism may be associated with central hypothyroidism, preserved fertility, and autosomal dominant inheritance, requiring increased attention to thyroid management during pregnancy.

PATIENT FINDINGS

A woman with a history of growth hormone deficiency and central hypothyroidism gave birth to a term male neonate appropriate for gestational age. Due to low thyrotropin (TSH) in the second trimester, the levothyroxine dose was decreased by the obstetrician, and free T4 was low throughout the latter half of pregnancy. The neonatal laboratory evaluation showed central hypothyroidism with a low T4 of 2.1 μg/dL (4.5-11.5) and an inappropriately normal TSH of 0.98 uIU/mL (0.5-4.5); undetectable growth hormone, IGF-I, and IGFBP3; a normal cortisol level; and a normal gonadotropin surge. After initiation of levothyroxine in the first week, both tone and feeding tolerance improved. However, the patient was found to have hearing loss, gross motor delay, and speech delay.

SUMMARY

In this report, we review a case of vertical transmission of a dominant negative POU1F1 mutation in which fetal abnormalities due to the hypothyroxinemic state during gestation may have been exacerbated by a decrease in the mother's levothyroxine dose based on a low TSH in early gestation. Both mother and fetus were unable to synthesize sufficient thyroid hormone, which may be responsible for the patient's clinical presentation.

CONCLUSION

This case underscores several important points in the management of women with hypopituitarism. First, it is important that patients and clinicians are both aware of the differences in etiology, as well as appropriate screening and treatment, of primary versus central hypothyroidism. Second, it is necessary to monitor the thyroid hormone status closely during pregnancy to prevent fetal sequelae of maternal hypothyroidism. Third, genetic screening of patients with combined pituitary hormone deficiency is necessary, so that prenatal genetic counseling may be an option for expecting parents.

Molecular and Clinical Findings in Patients with LHX4 and OTX2 Mutations

The pituitary gland produces hormones that play important roles in both the development and homeostasis of the body. Ontogeny of the anterior and posterior pituitary is orchestrated by inputs from neighboring tissues, cellular signaling molecules and transcription factors. Disruption of expression or function of these factors has been implicated in the etiology of combined pituitary hormone deficiency (CPHD). These include the transcription factors HESX1, PROP1, POU1F1, LHX3, LHX4, OTX2, SOX2, SOX3 and GLI2. This review focuses on summarizing most recent mutations in LHX4 and OTX2 responsible for pituitary hormone deficiency. In both genetic defects of LHX4 and OTX2, there is high variability in clinical manifestations even in the same family. In addition, there is no clear phenotype-genotype correlation. These findings indicate that the other genetic and/or environmental factors influence the phenotype. In addition, the variability might reflect a plasticity during pituitary development and maintenance. Over the past two decades, a genetic basis for pituitary hormone deficiency and the mechanism of pituitary development have been clarified. It should be kept in mind that this review is not comprehensive, and defects of other transcriptional factors have been described in patients with CPHD. Furthermore, the causes in many patients with CPHD have not yet been determined. Therefore, continuing efforts for the clarification of the etiology are necessary.

Molecular and Clinical Findings in Patients with LHX4 and OTX2 Mutations

The pituitary gland produces hormones that play important roles in both the development and homeostasis of the body. Ontogeny of the anterior and posterior pituitary is orchestrated by inputs from neighboring tissues, cellular signaling molecules and transcription factors. Disruption of expression or function of these factors has been implicated in the etiology of combined pituitary hormone deficiency (CPHD). These include the transcription factors HESX1, PROP1, POU1F1, LHX3, LHX4, OTX2, SOX2, SOX3 and GLI2. This review focuses on summarizing most recent mutations in LHX4 and OTX2 responsible for pituitary hormone deficiency. In both genetic defects of LHX4 and OTX2, there is high variability in clinical manifestations even in the same family. In addition, there is no clear phenotype-genotype correlation. These findings indicate that the other genetic and/or environmental factors influence the phenotype. In addition, the variability might reflect a plasticity during pituitary development and maintenance. Over the past two decades, a genetic basis for pituitary hormone deficiency and the mechanism of pituitary development have been clarified. It should be kept in mind that this review is not comprehensive, and defects of other transcriptional factors have been described in patients with CPHD. Furthermore, the causes in many patients with CPHD have not yet been determined. Therefore, continuing efforts for the clarification of the etiology are necessary.

Gradual loss of ACTH due to a novel mutation in LHX4: comprehensive mutation screening in Japanese patients with congenital hypopituitarism

Mutations in transcription factors genes, which are well regulated spatially and temporally in the pituitary gland, result in congenital hypopituitarism (CH) in humans. The prevalence of CH attributable to transcription factor mutations appears to be rare and varies among populations.

This study aimed to define the prevalence of CH in terms of nine CH-associated genes among Japanese patients. We enrolled 91 Japanese CH patients for DNA sequencing of POU1F1, PROP1, HESX1, LHX3, LHX4, SOX2, SOX3, OTX2, and GLI2. Additionally, gene copy numbers for POU1F1, PROP1, HESX1, LHX3, and LHX4 were examined by multiplex ligation-dependent probe amplification. The gene regulatory properties of mutant LHX4 proteins were characterized in vitro. We identified two novel heterozygous LHX4 mutations, namely c.249-1G>A, p.V75I, and one common POU1F1 mutation, p.R271W. The patient harboring the c.249-1G>A mutation exhibited isolated growth hormone deficiency at diagnosis and a gradual loss of ACTH, whereas the patient with the p.V75I mutation exhibited multiple pituitary hormone deficiency. In vitro experiments showed that both LHX4 mutations were associated with an impairment of the transactivation capacities of POU1F1 andαGSU, without any dominant-negative effects. The total mutation prevalence in Japanese CH patients was 3.3%. This study is the first to describe, a gradual loss of ACTH in a patient carrying an LHX4 mutation. Careful monitoring of hypothalamic–pituitary -adrenal function is recommended for CH patients with LHX4 mutations.

Genetic causes of combined pituitary hormone deficiencies in humans

Congenital hypopituitarism is a rare disease, usually induced by mutations of genes coding for transcription factors involved in pituitary development. PROP1 mutations represent the first cause of identified congenital hypopituitarism. Current techniques only identify 10-20% of congenital hypopituitarism etiologies, suggesting that new techniques are needed to improve this ratio. This should lead to a better management and follow-up of patients presenting with combined pituitary hormone deficiencies.

The use of neuroimaging for assessing disorders of pituitary development

Magnetic resonance imaging (MRI) is the radiological examination method of choice for evaluating hypothalamo-pituitary-related endocrine disease and is considered essential in the assessment of patients with suspected hypothalamo-pituitary pathology. Physicians involved in the care of such patients have, in MRI, a valuable tool that can aid them in determining the pathogenesis of their patients' underlying pituitary conditions. Indeed, the use of MRI has led to an enormous increase in our knowledge of pituitary morphology, improving, in particular, the differential diagnosis of hypopituitarism. Specifically, MRI allows detailed and precise anatomical study of the pituitary gland by differentiating between the anterior and posterior pituitary lobes. MRI recognition of pituitary hyperintensity in the posterior part of the sella, now considered a marker of neurohypophyseal functional integrity, has been the most striking finding in the diagnosis and understanding of certain forms of 'idiopathic' and permanent growth hormone deficiency (GHD). Published data show a number of correlations between pituitary abnormalities as observed on MRI and a patient's endocrine profile. Indeed, several trends have emerged and have been confirmed: (i) a normal MRI or anterior pituitary hypoplasia generally indicates isolated growth hormone deficiency that is mostly transient and resolves upon adult height achievement; (ii) patients with multiple pituitary hormone deficiencies (MPHD) seldom show a normal pituitary gland; and (iii) the classic triad of ectopic posterior pituitary, pituitary stalk hypoplasia/agenesis and anterior pituitary hypoplasia is more frequently reported in MPHD patients and is generally associated with permanent GHD. Pituitary abnormalities have also been reported in patients with hypopituitarism carrying mutations in several genes encoding transcription factors. Establishing endocrine and MRI phenotypes is extremely useful for the selection and management of patients with hypopituitarism, both in terms of possible genetic counselling and in the early diagnosis of evolving anterior pituitary hormone deficiencies. Going forward, neuroimaging techniques are expected to progressively expand and improve our knowledge and understanding of pituitary diseases.

Panhypopituitarism presenting as life-threatening heart failure caused by an inherited microdeletion in 1q25 including LHX4

Clinical presentation of hypopituitarism in the neonate may be variable, ranging from absent to severe nonspecific symptoms and may be life-threatening in patients with adrenocorticotropic hormone deficiency. The LIM homeobox gene 4 (LHX4) transcription factor regulates early embryonic development of the anterior pituitary gland. Autosomal dominant mutations in LHX4 cause congenital hypopituitarism with variable combined pituitary hormone deficiency (CPHD). We report on a neonate with unexplained heart failure and minor physical anomalies, suggesting a midline defect. She was diagnosed with complete CPHD. Cardiac function was rescued by replacement with hydrocortisone and thyroxine; hypoglycaemia stopped under growth hormone therapy. Magnetic resonance imaging revealed a dysgenetic pituitary gland suggesting an early developmental defect. Array comparative genomic hybridization showed a maternally inherited 1.5-megabase microdeletion in 1q25.2q25.3, including the LHX4 gene. Haploinsufficiency of LHX4 likely explains the predominant pituitary phenotype in the proposita and we suggest variable intrafamilial penetrance of the inherited microdeletion. To the best of our knowledge, we are the first to report on heart failure as a rare nonspecific symptom of treatable CPHD in the newborn. Variably penetrant pituitary insufficiency, including this severe and atypical presentation, can be correlated with LHX4 insufficiency and highlights the role of LHX4 for pituitary development.

PITX2 AND PITX1 regulate thyrotroph function and response to hypothyroidism

Pitx2 is a homeodomain transcription factor required in a dose-dependent manner for the development of multiple organs. Pitx2-null homozygotes (Pitx2(-/-)) have severe pituitary hypoplasia, whereas mice with reduced-function alleles (Pitx2(neo/neo)) exhibit modest hypoplasia and reduction in the developing gonadotroph and Pou1f1 lineages. PITX2 is expressed broadly in Rathke's pouch and the fetal pituitary gland. It predominates in adult thyrotrophs and gonadotrophs, although it is not necessary for gonadotroph function. To test the role of PITX2 in thyrotroph function, we developed thyrotroph-specific cre transgenic mice, Tg(Tshb-cre) with a recombineered Tshb bacterial artificial chromosome that ablates floxed genes in differentiated pituitary thyrotrophs. We used the best Tg(Tshb-Cre) strain to generate thyrotroph-specific Pitx2-deficient offspring, Pitx2(flox/-;)Tg(Tshb-cre). Double immunohistochemistry confirmed Pitx2 deletion. Pitx2(flox/-);Tg(Tshb-cre) mice have a modest weight decrease. The thyroid glands are smaller, although circulating T(4) and TSH levels are in the normal range. The pituitary levels of Pitx1 transcripts are significantly increased, suggesting a compensatory mechanism. Hypothyroidism induced by low-iodine diet and oral propylthiouracil revealed a blunted TSH response in Pitx2(flox/-);Tg(Tshb-cre) mice. Pitx1 transcripts increased significantly in control mice with induced hypothyroidism, but they remained unchanged in Pitx2(flox/-);Tg(Tshb-cre) mice, possibly because Pitx1 levels were already maximally elevated in untreated mutants. These results suggest that PITX2 and PITX1 have overlapping roles in thyrotroph function and response to hypothyroidism. The novel cre transgene that we report will be useful for studying the function of other genes in thyrotrophs.

Detection of genetic hypopituitarism in an adult population of idiopathic pituitary insufficiency patients with growth hormone deficiency

Idiopathic pituitary insufficiency (IPI) is diagnosed in 10% of all hypopituitary patients. There are several known and unknown aetiologies within the IPI group. The aim of this study was to investigate an adult IPI population for genetic cause according a screening schedule. From files of 373 GH deficient (GHD) patients on GH replacement 50 cases with IPI were identified. Of the 39 patients that approved to the study, 25 patients were selected for genetic investigation according to phenotype and 14 patients were not further tested, as sporadic isolated GHD (n = 9) and GHD with diabetes insipidus (n = 5) have low probability for a known genetic cause. Genotyping of all coding exons of HESX1, LHX4, PROP1, POU1F1 and GH1 genes were performed according to a diagnostic algorithm based on clinical, hormonal and neuroradiological phenotype. Among the 25 patients, an overall rate of 8% of mutations was found, and a 50% rate in familial cases. Among two sibling pairs, one pair that presented with complete anterior pituitary insufficiency, had a compound heterozygous PROP1 gene mutation (codons 117 and 120: exon 3 p Phe 117 Ile (c349 T>A) and p Arg 120 Cys (c358 C>T)) with a phenotype of very late onset ACTH-insufficiency. In the other sibling pair and in the sporadic cases no mutation was identified. This study suggests that currently known genetic causes are rare in sporadic adult IPI patients, and that systematic genetic screening is not needed in adult-onset sporadic cases of IPI. Conversely, familial cases are highly suspect for genetic causes.

Pituitary stem cell update and potential implications for treating hypopituitarism

Stem cells have been identified in organs with both low and high cell turnover rates. They are characterized by the expression of key marker genes for undifferentiated cells, the ability to self-renew, and the ability to regenerate tissue after cell loss. Several recent reports present evidence for the presence of pituitary stem cells. Here we offer a critical review of the field and suggest additional studies that could resolve points of debate. Recent reports have relied on different markers, including SOX2, nestin, GFRa2, and SCA1, to identify pituitary stem cells and progenitors. Future studies will be needed to resolve the relationships between cells expressing these markers. Members of the Sox family of transcription factors are likely involved in the earliest steps of pituitary stem cell proliferation and the earliest transitions to differentiation. The transcription factor PROP1 and the NOTCH signaling pathway may regulate the transition to differentiation. Identification of the stem cell niche is an important step in understanding organ development. The niche may be the marginal zone around the lumen of Rathke's pouch, between the anterior and intermediate lobes of mouse pituitary, because cells in this region apparently give birth to all six pituitary hormone cell lineages. Stem cells have been shown to play a role in recurrent malignancies in some tissues, and their role in pituitary hyperplasia, pituitary adenomas, and tumors is an important area for future investigation. From a therapeutic viewpoint, the ability to cultivate and grow stem cells in a pituitary predifferentiation state might also be helpful for the long-term treatment of pituitary deficiencies.

The role of homeodomain transcription factors in heritable pituitary disease

The anterior pituitary gland secretes hormones that regulate developmental and physiological processes, including growth, the stress response, metabolic status, reproduction and lactation. During embryogenesis, cellular determination and differentiation events establish specialized hormone-secreting cell types within the anterior pituitary gland. These developmental decisions are mediated in part by the actions of a cascade of transcription factors, many of which belong to the homeodomain class of DNA-binding proteins. The discovery of some of these regulatory proteins has facilitated genetic analyses of patients with hormone deficiencies. The findings of these studies reveal that congenital defects-ranging from isolated hormone deficiencies to combined pituitary hormone deficiency syndromes-are sometimes associated with mutations in the genes encoding pituitary-acting developmental transcription factors. The phenotypes of affected individuals and animal models have together provided useful insights into the biology of these transcription factors and have suggested new hypotheses for testing in the basic science laboratory. Here, we summarize the gene regulatory pathways that control anterior pituitary development, with emphasis on the role of the homeodomain transcription factors in normal pituitary organogenesis and heritable pituitary disease.

[Genetic aspects of growth hormone deficiency]

Congenital growth hormone deficiency (GHD) is a rare cause of growth delay. It should be suspected when other causes of hypopituitarism (sellar tumor, postsurgical or radioinduced hypopituitarism, etc.) have been ruled out. GHD can be isolated (IGHD) or associated with at least one other pituitary hormone deficiency (CPHD) including thyrotroph, lactotroph, corticotroph, or gonadotroph deficiencies. CPHD is caused by mutations of genes coding for pituitary transcription factors involved in pituitary ontogenesis or in the hypothalamic-pituitary axis. Clinical presentation varies, depending on the type and severity of GHD, the age at diagnosis, the association with other pituitary hormone deficiencies, or extrapituitary malformations. Clinical, biological, and radiological work-up is very important to determine for which transcription factor the patient should be screened. There is a wide variety of phenotypes depending on the transcription factor involved: PROP1 (somatolactotroph, thyrotroph, gonadotroph, and sometimes corticotroph deficiencies ; pituitary hyper- or hypoplasia), POU1F1 (somatolactotroph and thyrotroph deficiencies, pituitary hypoplasia), HESX1 (variable pituitary deficiencies, septo-optic dysplasia), and less frequently LHX3 (somatolactotroph, thyrotroph, and gonadotroph deficiencies, deafness, and limited head and neck rotation), LHX4 (variable pituitary deficiencies, ectopic neurohypophysis, cerebral abnormalities), and OTX2 (variable pituitary deficiencies, ectopic neurohypophysis, ocular abnormalities). Mutations of PROP1 remain the first identified cause of CPHD, and as a consequence the first to be sought. POU1F1 mutations should be looked for in the postpubertal population presenting with GH/TSH deficiencies and no extrapituitary malformations. Once genetic diagnosis has been concluded, a strict follow-up is necessary because patients can develop new deficiencies (for example, late-onset corticotroph deficiency in patients with PROP1 mutations). Identification of gene defects allows early treatment of pituitary deficiency and prevention of their potentially lethal consequences. If untreated, the main symptoms include short stature, cognitive alterations, or delayed puberty. An appropriate replacement of hormone deficiencies is therefore required. Depending on the type of transmission (recessive transmission for PROP1 and LHX3, dominant for LHX4, autosomal dominant or recessive for POU1F1 and HESX1), genetic counseling might be proposed. Genotyping appears highly beneficial at an individual and familial level.

17q21.31 microdeletion in a patient with pituitary stalk interruption syndrome

We report the case of a 26-month-old boy with mental retardation, facial dysmorphism, childhood feeding difficulties, short stature, bilateral cryptorchidism, micropenis, and heart defect. Endocrinal evaluation revealed complete growth hormone deficiency (GHD) and gonadotropic deficiency, and pituitary magnetic resonance imaging showed partial pituitary stalk interruption syndrome (PSIS). A de novo 493 kb microdeletion on chromosome 17q21.31 was identified using array comparative genomic hybridization (array-CGH) analysis. This is the first report of PSIS in the phenotypical spectrum of 17q21.31 microdeletion syndrome, although other midline abnormalities have previously been described. Our report suggests that GHD should be investigated in patients with 17q21.31 microdeletion syndrome and short stature, defined by a body height below - 2 standard deviation scores (SDS) for age and sex. This finding also opens new avenues of research on the etiopathogenesis of PSIS, for which the genetic mechanisms remain unknown.

Pituitary transcription factors in the aetiology of combined pituitary hormone deficiency

The somatotropic axis is the central postnatal regulator of longitudinal growth. One of its major components--growth hormone--is produced by the anterior lobe of the pituitary, which also expresses and secretes five additional hormones (prolactin, thyroid stimulating hormone, follicle stimulating hormone, luteinizing hormone, adrenocorticotropic hormone). Proper development of the pituitary assures the regulation of critical processes such as metabolic control, puberty and reproduction, stress response and lactation. Ontogeny of the adenohypophysis is orchestrated by inputs from neighbouring tissues, cellular signalling molecules and transcription factors. Perturbation of expression or function of these factors has been implicated in the aetiology of combined pituitary hormone deficiency (CPHD). Mutations within the genes encoding for the transcription factors LHX3, LHX4, PROP1, and POU1F1 (PIT1) that act at different stages of pituitary development result in unique patterns of hormonal deficiencies reflecting their differential expression during organogenesis. In the case of LHX3 and LHX4 the phenotype may include extra-pituitary manifestations due to the function of these genes/proteins outside the pituitary gland. The remarkable variability in the clinical presentation of affected patients indicates the influence of the genetic background, environmental factors and possibly stochastic events. However, in the majority of CPHD cases the aetiology of this heterogeneous disease remains unexplained, which further suggests the involvement of additional genes. Identification of these factors might also help to close the gaps in our understanding of pituitary development, maintenance and function.

Mutation and gene copy number analyses of six pituitary transcription factor genes in 71 patients with combined pituitary hormone deficiency: identification of a single patient with LHX4 deletion

CONTEXT

Mutations of multiple transcription factor genes involved in pituitary development have been identified in a minor portion of patients with combined pituitary hormone deficiency (CPHD). However, copy number aberrations involving such genes have been poorly investigated in patients with CPHD.

OBJECTIVE

We aimed to report the results of mutation and gene copy number analyses in patients with CPHD.

SUBJECTS AND METHODS

Seventy-one Japanese patients with CPHD were examined for mutations and gene copy number aberrations affecting POU1F1, PROP1, HESX1, LHX3, LHX4, and SOX3 by PCR-direct sequencing and multiplex ligation-dependent probe amplification. When a deletion was indicated, it was further studied by fluorescence in situ hybridization, oligoarray comparative genomic hybridization, and serial sequencing for long PCR products encompassing the deletion junction.

RESULTS

We identified a de novo heterozygous 522,009-bp deletion involving LHX4 in a patient with CPHD (GH, TSH, PRL, LH, and FSH deficiencies), anterior pituitary hypoplasia, ectopic posterior pituitary, and underdeveloped sella turcica. We also identified five novel heterozygous missense substitutions (p.V201I and p.H387P in LHX4, p.T63M and p.A322T in LHX3, and p.V53L in SOX3) that were assessed as rare variants by sequencing analyses for control subjects and available parents and by functional studies and in silico analyses.

CONCLUSIONS

The results imply the rarity of abnormalities affecting the six genes in patients with CPHD and the significance of the gene copy number analysis in such patients.

Molecular mechanisms of pituitary organogenesis: In search of novel regulatory genes

Defects in pituitary gland organogenesis are sometimes associated with congenital anomalies that affect head development. Lesions in transcription factors and signaling pathways explain some of these developmental syndromes. Basic research studies, including the characterization of genetically engineered mice, provide a mechanistic framework for understanding how mutations create the clinical characteristics observed in patients. Defects in BMP, WNT, Notch, and FGF signaling pathways affect induction and growth of the pituitary primordium and other organ systems partly by altering the balance between signaling pathways. The PITX and LHX transcription factor families influence pituitary and head development and are clinically relevant. A few later-acting transcription factors have pituitary-specific effects, including PROP1, POU1F1 (PIT1), and TPIT (TBX19), while others, such as NeuroD1 and NR5A1 (SF1), are syndromic, influencing development of other endocrine organs. We conducted a survey of genes transcribed in developing mouse pituitary to find candidates for cases of pituitary hormone deficiency of unknown etiology. We identified numerous transcription factors that are members of gene families with roles in syndromic or non-syndromic pituitary hormone deficiency. This collection is a rich source for future basic and clinical studies.

Genetic regulation of pituitary gland development in human and mouse

Normal hypothalamopituitary development is closely related to that of the forebrain and is dependent upon a complex genetic cascade of transcription factors and signaling molecules that may be either intrinsic or extrinsic to the developing Rathke's pouch. These factors dictate organ commitment, cell differentiation, and cell proliferation within the anterior pituitary. Abnormalities in these processes are associated with congenital hypopituitarism, a spectrum of disorders that includes syndromic disorders such as septo-optic dysplasia, combined pituitary hormone deficiencies, and isolated hormone deficiencies, of which the commonest is GH deficiency. The highly variable clinical phenotypes can now in part be explained due to research performed over the last 20 yr, based mainly on naturally occurring and transgenic animal models. Mutations in genes encoding both signaling molecules and transcription factors have been implicated in the etiology of hypopituitarism, with or without other syndromic features, in mice and humans. To date, mutations in known genes account for a small proportion of cases of hypopituitarism in humans. However, these mutations have led to a greater understanding of the genetic interactions that lead to normal pituitary development. This review attempts to describe the complexity of pituitary development in the rodent, with particular emphasis on those factors that, when mutated, are associated with hypopituitarism in humans.