Allelic Variants in Established Hypopituitarism Genes Expand Our Knowledge of the Phenotypic Spectrum.

We report four allelic variants (three novel) in three genes previously established as causal for hypopituitarism or related disorders. A novel homozygous variant in the growth hormone gene, GH1 c.171delT (p.Phe 57Leufs*43), was found in a male patient with severe isolated growth hormone deficiency (IGHD) born to consanguineous parents. A hemizygous SOX3 allelic variant (p.Met304Ile) was found in a male patient with IGHD and hypoplastic anterior pituitary. YASARA, a tool to evaluate protein stability, suggests that p.Met304Ile destabilizes the SOX3 protein (ΔΔG = 2.49 kcal/mol). A rare, heterozygous missense variant in the TALE homeobox protein gene, TGIF1 (c.268C>T:p.Arg90Cys) was found in a patient with combined pituitary hormone deficiency (CPHD), diabetes insipidus, and syndromic features of holoprosencephaly (HPE). This variant was previously reported in a patient with severe holoprosencephaly and shown to affect TGIF1 function. A novel heterozygous TGIF1 variant (c.82T>C:p.Ser28Pro) was identified in a patient with CPHD, pituitary aplasia and ectopic posterior lobe. Both TGIF1 variants have an autosomal dominant pattern of inheritance with incomplete penetrance. In conclusion, we have found allelic variants in three genes in hypopituitarism patients. We discuss these variants and associated patient phenotypes in relation to previously reported variants in these genes, expanding our knowledge of the phenotypic spectrum in patient populations.

High-throughput splicing assays identify missense and silent splice-disruptive POU1F1 variants underlying pituitary hormone deficiency.

Pituitary hormone deficiency occurs in ∼1:4,000 live births. Approximately 3% of the cases are due to mutations in the alpha isoform of POU1F1, a pituitary-specific transcriptional activator. We found four separate heterozygous missense variants in unrelated individuals with hypopituitarism that were predicted to affect a minor isoform, POU1F1 beta, which can act as a transcriptional repressor. These variants retain repressor activity, but they shift splicing to favor the expression of the beta isoform, resulting in dominant-negative loss of function. Using a high-throughput splicing reporter assay, we tested 1,070 single-nucleotide variants in POU1F1. We identified 96 splice-disruptive variants, including 14 synonymous variants. In separate cohorts, we found two additional synonymous variants nominated by this screen that co-segregate with hypopituitarism. This study underlines the importance of evaluating the impact of variants on splicing and provides a catalog for interpretation of variants of unknown significance in POU1F1.

The phenotypic spectrum associated with OTX2 mutations in humans.

Objective: The transcription factor OTX2 is implicated in ocular, craniofacial, and pituitary development. Design: We aimed to establish the contribution of OTX2 mutations in congenital hypopituitarism patients with/without eye abnormalities, study functional consequences, and establish OTX2 expression in the human brain, with a view to investigate the mechanism of action. Methods: We screened patients from the UK (n = 103), international centres (n = 24), and Brazil (n = 282); 145 were within the septo-optic dysplasia spectrum, and 264 had no eye phenotype. Transactivation ability of OTX2 variants was analysed in murine hypothalamic GT1-7 neurons. In situ hybridization was performed on human embryonic brain sections. Genetically engineered mice were generated with a series of C-terminal OTX2 variants. Results: Two chromosomal deletions and six haploinsufficient mutations were identified in individuals with eye abnormalities; an affected relative of one patient harboured the same mutation without an ocular phenotype. OTX2 truncations led to significant transactivation reduction. A missense variant was identified in another patient without eye abnormalities; however, studies revealed it was most likely not causative. In the mouse, truncations proximal to aa219 caused anophthalmia, while distal truncations and the missense variant were tolerated. During human embryogenesis, OTX2 was expressed in the posterior pituitary, retina, ear, thalamus, choroid plexus, and partially in the hypothalamus, but not in the anterior pituitary. Conclusions: OTX2 mutations are rarely associated with hypopituitarism in isolation without eye abnormalities, and may be variably penetrant, even within the same pedigree. Our data suggest that the endocrine phenotypes in patients with OTX2 mutations are of hypothalamic origin.

A Bayesian Approach to Diagnose Growth Hormone Deficiency in Children: Insulin-Like Growth Factor Type 1 Is Valuable for Screening and IGF-Binding Protein Type 3 for Confirmation.

BACKGROUND: The utility of insulin-like growth factor type 1 (IGF-1) is well established in the diagnosis of growth hormone deficiency (GHD), whereas IGF-binding protein type 3 (IGFBP-3) has a more controversial role. Most studies evaluated the value of these peptides by assessing their sensitivity and specificity but not considering the low prevalence of GHD among short children (<2%). OBJECTIVE: To evaluate the utility of basal IGF-1 and IGFBP-3 values in the GHD diagnosis process with a Bayesian approach, based on pre- and post-test probability. METHODS: We determined ROC curves, sensitivity, specificity, and positive and negative predictive values for IGF-1 and IGFBP-3 obtained from patients with GHD (n = 48) and GH-sufficient children (n = 175). The data were also analyzed by classifying the children into early childhood and late childhood (girls and boys younger and older than 8 and 9 years, respectively). RESULTS: The area under the curve (AUC) of the receiver operating characteristic curve of IGF-1-SDS (standard deviation score) was greater than that of IGFBP-3-SDS (AUC 0.886 and 0.786, respectively, p = 0.001). In early childhood, the AUC of IGFBP-3-SDS was significantly improved (0.866) and similar to IGF-1-SDS (0.898). IGF-1-SDS, in comparison to IGFBP-3-SDS, had a greater sensitivity (92 vs. 45.8%, respectively), lower specificity (69 vs. 93.8%, respectively), and lower positive predictive value (5.7 vs. 13.1%, respectively), with similar negative predictive values. CONCLUSION: IGF-1-SDS is a useful screening tool in the diagnosis of GHD. Although IGFBP-3-SDS lacks sensitivity, its high specificity supports the role to confirm GHD in short children, especially in early childhood. This strategy could simplify and reduce the necessity of a second laborious and expensive GH stimulation test to confirm the diagnosis of GHD.

Combined pituitary hormone deficiency caused by PROP1 mutations: update 20 years post-discovery.

The first description of patients with combined pituitary hormone deficiencies (CPHD) caused by PROP1 mutations was made 20 years ago. Here we updated the clinical and genetic characteristics of patients with PROP1 mutations and summarized the phenotypes of 14 patients with 7 different pathogenic PROP1 mutations followed at the Hospital das Clínicas of the University of Sao Paulo. In addition to deficiencies in GH, TSH, PRL and gonadotropins some patients develop late ACTH deficiency. Therefore, patients with PROP1 mutations require permanent surveillance. On magnetic resonance imaging, the pituitary stalk is normal, and the posterior lobe is in the normal position. The anterior lobe in patients with PROP1 mutations is usually hypoplastic but may be normal or even enlarged. Bi-allelic PROP1 mutations are currently the most frequently recognized genetic cause of CPHD worldwide. PROP1 defects occur more frequently among offspring of consanguineous parents and familial cases, but they also occur in sporadic cases, especially in countries in which the prevalence of PROP1 mutations is relatively high. We classified all reported PROP1 variants described to date according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP) guidelines: 29 were pathogenic, 2 were likely pathogenic, and 2 were of unknown significance. An expansion of the phenotype of patients with PROP1 mutations was observed since the first description 20 years ago: variable anterior pituitary size, different pathogenic mutations, and late development of ACTH deficiency. PROP1 mutations are the most common cause of autosomal recessive CPHD with a topic posterior pituitary lobe. Arch Endocrinol Metab. 2019;63(2):167-74.

Genetic diagnosis of congenital hypopituitarism by a target gene panel: novel pathogenic variants in GLI2, OTX2 and GHRHR.

AIM: Congenital hypopituitarism has an incidence of 1:3500-10,000 births and is defined by the impaired production of pituitary hormones. Early diagnosis has an impact on management and genetic counselling. The clinical and genetic heterogeneity of hypopituitarism poses difficulties to select the order of genes to analyse. The objective of our study is to screen hypopituitarism genes (candidate and previously related genes) simultaneously using a target gene panel in patients with congenital hypopituitarism. METHODS: Screening of 117 subjects with congenital hypopituitarism for pathogenic variants in 26 genes associated with congenital hypopituitarism by massively parallel sequencing using a customized target gene panel. RESULTS: We found three novel pathogenic variants in OTX2 c.295C>T:p.Gln99*, GLI2 c.1681G>T:p.Glu561* and GHRHR c.820_821insC:p.Asp274Alafs*113, and the previously reported variants in GHRHR c.57+1G>A and PROP1 [c.301_302delAG];[c.109+1G>A]. CONCLUSIONS: Our results indicate that a custom-designed panel is an efficient method to screen simultaneously variants of biological and clinical relevance for congenital GH deficiency. A genetic diagnosis was possible in 5 out of 117 (4%) patients of our cohort. We identified three novel pathogenic variants in GHRHR, OTX2 and GLI2 expanding the spectrum of variants associated with congenital hypopituitarism.

Combined pituitary hormone deficiency caused by PROP1 mutations: update 20 years post-discovery

ABSTRACT The first description of patients with combined pituitary hormone deficiencies (CPHD) caused by PROP1 mutations was made 20 years ago. Here we updated the clinical and genetic characteristics of patients with PROP1 mutations and summarized the phenotypes of 14 patients with 7 different pathogenic PROP1 mutations followed at the Hospital das Clínicas of the University of Sao Paulo. In addition to deficiencies in GH, TSH, PRL and gonadotropins some patients develop late ACTH deficiency. Therefore, patients with PROP1 mutations require permanent surveillance. On magnetic resonance imaging, the pituitary stalk is normal, and the posterior lobe is in the normal position. The anterior lobe in patients with PROP1 mutations is usually hypoplastic but may be normal or even enlarged. Bi-allelic PROP1 mutations are currently the most frequently recognized genetic cause of CPHD worldwide. PROP1 defects occur more frequently among offspring of consanguineous parents and familial cases, but they also occur in sporadic cases, especially in countries in which the prevalence of PROP1 mutations is relatively high. We classified all reported PROP1 variants described to date according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP) guidelines: 29 were pathogenic, 2 were likely pathogenic, and 2 were of unknown significance. An expansion of the phenotype of patients with PROP1 mutations was observed since the first description 20 years ago: variable anterior pituitary size, different pathogenic mutations, and late development of ACTH deficiency. PROP1 mutations are the most common cause of autosomal recessive CPHD with a topic posterior pituitary lobe. Arch Endocrinol Metab. 2019;63(2):167-74

IGF-1 assessed by pubertal status has the best positive predictive power for GH deficiency diagnosis in peripubertal children.

Background When evaluating peripubertal short stature patients, the interpretation of insulin-like growth factor 1 (IGF-1) levels based on chronological age (CA) can be inaccurate due to the influence of sex steroids and, presently, there is no evidence to support the assessment of IGF-1 values according to bone age (BA) and pubertal status (PS). Our objective was to assess the discriminatory performance of IGF-1 levels based on CA, BA and PS in the diagnosis of growth hormone (GH) deficiency. Methods We evaluated IGF-1 levels from 154 peripubertal short stature patients classified as GH deficient (GHD, n=23) or non-GHD (n=131). IGF-1 was assayed by a chemiluminescent immunometric assay and transformed into standard deviation scores (SDS) according to CA (IGF-1-SDS-CA), BA (IGF-1-SDS-BA) and PS (IGF-1-SDS-PS). Results The performances of IGF-1-SDS-CA, IGF-1-SDS-BA and IGF-1-SDS-PS in the receiver operator characteristics (ROC) curves were similar. There were greater accuracy and specificity of IGF-1-SDS-PS (98.4% and 93.3%, respectively) and IGF-1-SDS-BA (92.7% and 90.1%, respectively) when compared to IGF-1-SDS-CA (65.6% and 69.5%, respectively). The post-test probability of the IGF-1-SDS was also improved when compared to PS and BA - 44.8% (IGF-1-SDS-PS), 16.8% (IGF-1-SDS-BA) and 5.1% (IGF-1-SDS-CA), with similar negative predictive values. Conclusions The evaluation of IGF-1 levels based on CA has a higher sensitivity than those based on BA or PS, which justify its use as a screening tool. Additionally, IGF-1 assessed by PS has the best positive predictive power for GHD diagnosis in peripubertal age and could reduce the necessity of a second GH stimulation test.

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.

Molecular analysis of brazilian patients with combined pituitary hormone deficiency and orthotopic posterior pituitary lobe reveals eight different PROP1 alterations with three novel mutations.

BACKGROUND: Mutations in PROP1, HESX1 and LHX3 are associated with combined pituitary hormone deficiency (CPHD) and orthotopic posterior pituitary lobe (OPP). OBJECTIVE: To identify mutations in PROP1, HESX1 and LHX3 in a large cohort of patients with CPHD and OPP (35 Brazilian, two Argentinian). DESIGN AND METHODS: We studied 23 index patients with CPHD and OPP (six familial and 17 sporadic) as well as 14 relatives. PROP1 was sequenced by the Sanger method in all except one sporadic case studied using a candidate gene panel. Multiplex ligation-dependent probe amplification (MLPA) was applied to one familial case in whom PROP1 failed to amplify by PCR. In the 13 patients without PROP1 mutations, HESX1 and LHX3 were sequenced by the Sanger method. RESULTS: We identified PROP1 mutations in 10 index cases. Three mutations were novel: one affecting the initiation codon (c.1A>G) and two affecting splicing sites, c.109+1G>A and c.342+1G>C. The known mutations, c.150delA (p.Arg53Aspfs*112), c.218G>A (p.Arg73His), c.263T>C (p.Phe88Ser) and c.301_302delAG (p.Leu102Cysfs*8), were also detected. MLPA confirmed complete PROP1 deletion in one family. We did not identify HESX1 and LHX3 mutations by Sanger. CONCLUSION: PROP1 mutations are a prevalent cause of congenital CPHD with OPP, and therefore, PROP1 sequencing must be the first step of molecular investigation in patients with CPHD and OPP, especially in populations with a high frequency of PROP1 mutations. In the absence of mutations, massively parallel sequencing is a promising approach. The high prevalence and diversity of PROP1 mutations is associated with the ethnic background of this cohort.