Update on new GH-IGF axis genetic defects

ABSTRACT The somatotropic axis is the main hormonal regulator of growth. Growth hormone (GH), also known as somatotropin, and insulin-like growth factor 1 (IGF-1) are the key components of the somatotropic axis. This axis has been studied for a long time and the knowledge of how some molecules could promote or impair hormones production and action has been growing over the last decade. The enhancement of large-scale sequencing techniques has expanded the spectrum of known genes and several other candidate genes that could affect the GH-IGF1-bone pathway. To date, defects in more than forty genes were associated with an impairment of the somatotropic axis. These defects can affect from the secretion of GH to the bioavailability and action of IGF-1. Affected patients present a large heterogeneous group of conditions associated with growth retardation. In this review, we focus on the description of the GH-IGF axis genetic defects reported in the last decade. Arch Endocrinol Metab. 2019;63(6):608-17

Genetic causes of isolated short stature

ABSTRACT Short stature is a common feature, and frequently remains without a specific diagnosis after conventional clinical and laboratorial evaluation. Longitudinal growth is mainly determined by genetic factors, and hundreds of common variants have been associated to height variability among healthy individuals. Although isolated short stature may be caused by the combination of variants, with a deleterious impact on the growth of individuals with polygenic inheritance, recent studies have pointed out some monogenic defects as the cause of the growth disorder observed in nonsyndromic children. The majority of these defects are in genes related to the growth plate cartilage and in the growth hormone (GH) - insulin-like growth factor 1 (IGF-1) axis. Affected patients usually present the mildest spectrum of some forms of skeletal dysplasia, or subtle abnormalities of laboratory tests, suggesting hormonal resistance or insensibility. The lack of specific characteristics, however, does not allow formulation of a definitive diagnosis without the use of broad genetic studies. Thus, molecular genetic studies including panels of genes or exome analysis will become essential in investigating and identifying the causes of isolated short stature in children, with a crucial impact on treatment and follow-up.

Molecular characterization in a case of isolated growth hormone deficiency and further prenatal diagnosis of an unborn sibling.

Familial isolated growth hormone deficiency (GHD) type 1 is characterized by an autosomal recessive pattern of inheritance with varying degrees of phenotypic severity. We report a proband, with isolated GHD (IGHD) with very early growth arrest and undetectable levels of GH. Homozygous complete deletion of the GH1 gene was identified by real‑time/quantitative polymerase chain reaction (RT/q‑PCR) and confirmed by an independent molecular genetic method; the multiplex ligation‑dependent probe amplification (MLPA) technique. Prenatal diagnosis was offered for the subsequent pregnancy in the mother of our proband. Identical heterozygous deletion of the GH1 gene was detected in both parents. The fetus had a similar homozygous deletion of the GH1 gene. We thus report a unique case with a confirmed mutation in GH1 gene in the proband followed by prenatal detection of the same mutation in the amniotic fluid which to our knowledge hitherto has not been documented from India.

Deficiência da STAT5B: uma nova síndrome de insensibilidade ao hormônio de crescimento associada a acometimento imunológico / STAT5B deficiency: a new growth hormone insensitivity syndrome associated to immunological dysfunction

Uma nova apresentação da insensibilidade ao hormônio de crescimento (IGH), causada por mutações em homozigose no gene STAT5B (transdutor de sinal e ativador de transcrição tipo 5B), foi caracterizada nos últimos anos. Sua particularidade é a associação com quadros de disfunção imunológica grave, sendo o mais característico a pneumonite intersticial linfocítica. A presença concomitante de doenças crônicas imunológicas pode fazer com que a baixa estatura seja erroneamente considerada uma consequência do quadro clínico, levando ao subdiagnóstico dessa forma de IGH. O objetivo desta revisão é divulgar o conhecimento atual sobre essa rara patologia, facilitando o reconhecimento de pacientes com IGH secundária a mutações no gene STAT5B em ambulatórios de endocrinologia e de outras especialidades.

A new presentation of growth hormone insensitivity (GHI) caused by homozygous mutations in STAT5B (signal transducer and activator of transcription 5B) gene has been characterized in the last years. Its particularity is the association with severe immune dysfunction, especially with lymphocytic interstitial pneumonitis. This may mislead physicians into considering short stature as secondary to chronic immunological disease and consequently into underdiagnosing this form of GHI. The objective of this review is to propagate current knowledge about this rare pathology, facilitating the diagnosis of patients with GHI due to STAT5B mutations in endocrinology and other specialties clinics.

Type IA isolated growth hormone deficiency (IGHD) consistent with compound heterozygous deletions of 6.7 and 7.6 Kb at the GH1 gene locus / Deficiência isolada de hormônio do crescimento tipo IA (DIGH) consistente com deleções heterozigotas compostas de 6,7 e 7,6 Kb no locus gênico GH1

Isolated growth hormone deficiency (IGHD) may result from deletions/mutations in either GH1 or GHRHR genes. The objective of this study was to characterize the molecular defect in a girl presenting IGHD. The patient was born at 41 weeks of gestation from non-consanguineous parents. Clinical and biochemical evaluation included anthropometric measurements, evaluation of pituitary function, IGF-I and IGFBP-3 levels. Molecular characterization was performed by PCR amplification of GH1 gene and SmaI digestion of two homologous fragments flanking the gene, using genomic DNA from the patient and her parents as templates. At 1.8 years of age the patient presented severe growth retardation (height 61.2 cm, -7.4 SDS), truncal obesity, frontal bossing, doll face, and acromicria. MRI showed pituitary hypoplasia. Laboratory findings confirmed IGHD. GH1 gene could not be amplified in samples from the patient while her parents yielded one fragment of the expected size. SmaI digestion was consistent with the patient being compound heterozygous for 6.7 and 7.6 Kb deletions, while her parents appear to be heterozygous carriers for either the 6.7 or the 7.6 Kb deletions. We have characterized type IA IGHD caused by two different GH1 gene deletions, suggesting that this condition should be considered in severe IGHD, even in non-consanguineous families. Arq Bras Endocrinol Metab. 2012;56(8):558-63.

A deficiência isolada do hormônio do crescimento (DIGH) pode ser resultado de deleções/mutações no gene GH1 ou no gene GHRHR. O objetivo deste estudo foi caracterizar o defeito molecular em uma menina que apresenta DIGH. A paciente nasceu às 41 semanas de gestação de pais não consanguíneos. As avaliações clínica e bioquímica incluíram medidas antropométricas, avaliação da função pituitária e concentrações de IGF-I e IGFBP-3. A caracterização molecular foi feita por meio de amplificação do GH1 por PCR e digestão com SmaI de dois fragmentos homólogos flanqueando o gene, usando-se DNA genômico da paciente e de seus pais como padrões. Com 1,8 ano de idade, a paciente apresentou atraso grave no crescimento (altura 61,2 cm, -7.4 DP), obesidade central, protuberância frontal, face de boneca e acromicria. A RM mostrou hipoplasia pituitária. Os achados laboratoriais confirmaram a DIGH. O gene GH1 não pôde ser amplificado nas amostras da paciente, enquanto as amostras de seus pais produziram um fragmento do tamanho esperado. A digestão com SmaI foi consistente com a paciente ser heterozigota composta para deleções para 6,7 e 7,6 Kb, enquanto seus pais parecem ser carreadores heterozigotos para deleções de 6,7 ou 7,6 Kb. Caracterizamos a DIGH tipo IA causada por duas deleções diferentes no gene GH1, sugerindo que essa condição pode ser considerada na DIGH grave, mesmo em famílias não consanguíneas. Arq Bras Endocrinol Metab. 2012;56(8):558-63.

Talla alta, sindrome XYY: presentación de un caso / High -Class, XYY Syndrome: case report

Los niños y hombres con el síndrome 47 XYY tienen dos cromosomas Y en vez de uno. Esto significa que tienen 47 cromoso- mas en lugar de 46. El cromosoma adicional se obtuvo durante la formación del esperma que se juntó con el óvulo al formar el feto o durante el desarrollo temprano del feto, justo después de la concepción. El cromo - soma extra no puede ser removido nunca. El síndrome 47 XYY ocurre al azar. (1). Algunos médicos genetistas cuestionan si el uso del término «síndrome¼ es apropiado para ésta anomalía, porque el fenotipo es normal. (2). Las personas 47 XYY , presentan un aspecto físico normal, y se caracterizan por una estatura alta, que se hace más evidente en la adolescencia. (1, 2, 3)...(AU)

Pesquisa de mutações no gene do receptor do secretagogo de hormônio de crescimento (GHSR) em crianças com baixa estatura idiopática e deficiência isolada de hormônio de crescimento / Growth hormone secretatogue receptor gene (GHSR) analysis in patients with idiopathic short stature (ISS) and patients with isolated growth hormone deficiency

A ghrelina, hormônio secretado principalmente por células gástricas, liga-se ao seu receptor, o receptor de secretagogo de GH (GHSR - Growth hormone secretagogue receptor), localizado no hipotálamo e na hipófise, estimulando a síntese e secreção do GH. Recentemente foram identificadas mutações no gene GHSR em crianças com baixa estatura idiopática (BEI) e com deficiência isolada de GH (DGH). No presente estudo investigamos a presença de mutações no gene GHSR em crianças com DGH isolada de causa não identificada e crianças com BEI, incluindo um subgrupo de crianças com atraso constitucional de crescimento e desenvolvimento (ACCD). Foram selecionados 14 pacientes com deficiência isolada de GH sem alterações anatômicas da região hipotálamo-hipofisária e 96 pacientes com BEI, destes 31 (32%) apresentavam ACCD. Também foram estudados 150 controles adultos e 197 crianças controle com crescimento e puberdade normais. A região codificadora do GHSR foi amplificada utilizando-se oligonucleotídeos iniciadores específicos, seguida de purificação enzimática e seqüenciamento automático. Encontramos 6 variantes alélicas em heterozigose no GHSR: nenhuma delas presente nos controles estudados, e quatro destas variantes estão localizadas em regiões conservadas do gene. Uma variante foi encontrada em uma paciente do grupo DGH (p.Val249Leu) e as outras cinco (c.-6 G>C, p.Ser84Ile, p.Val182Ala, p.Ala169Thr e p.Ala358Thr) foram encontradas em pacientes do subgrupo ACCD do grupo BEI. As variantes missense foram submetidas a estudo funcional que evidenciou que as mutações p.Ser84Ile e p.Val182Ala possuem diminuição na atividade basal associadas à diminuição da expressão do receptor na superfície celular. Adicionalmente, a mutação p.Ser84Ile também apresenta redução na atividade do GHSR induzida pelo ligante. A variante p.Val249Leu foi encontrada em uma paciente do sexo feminino com diagnóstico de DGH isolado...

Ghrelin, hormone secreted by gastric cells, stimulates growth hormone secretion by acting on its receptor GHSR, located in the hypothalamus and pituitary. Recently, mutations in the GHSR gene were described in patients with growth hormone deficiency (GHD) and idiopathic short stature (ISS). In the present study we analyzed the GHSR gene in patients with isolated GHD and patients with ISS, including a subgroup of patients with constitutional delay of growth and puberty (CDGP). We studied 14 GHD patients with normal pituitary magnetic resonance imaging and 96 patients with ISS, 31 of them with CDGP. We also studied 150 adults and in 197 children with normal stature. The entire coding region as well as the exon-intron boundaries of GHSR were PCR amplified in all patients and control group and PCR products were bidirectionally sequenced. Six different heterozygous variants in GHSR were identified: none of them were found in the control group and four of these amino acid substitutions occurred at a conserved position within the GHSR. One variant (p.Val249Leu) was found in a GHD patient and the other five (c.-6 G>C, p.Ser84Ile, p.Val182Ala, p.Ala169Thr e p.Ala358Thr) were found in patients with CDGP. The missense variants were submitted to functional studies. Two of these variants (p.Ser84Ile and p.Val182Ala) result in a decrease in basal activity that was in part explained by a reduction in cell surface expression. The p.Ser84Ile mutation was also associated with a defect in ghrelin potency. The p.Val249Leu variant, found in a female patient with isolated GHD, did not segregate with the phenotype in the family and had no functional impairment in vitro. This suggests that p.Val249Leu is not the cause of the GHD in the family and may be a rare allelic variant. The other variants (c.-6 G>C, p.Ser84Ile, p.Val182Ala, p.Ala169Thr e p.Ala358Thr) were identified only in patients with CDGP (3 male and 2 female)...

Bone age is the best predictor of growth response to recombinant human growth hormone in Turner’s syndrome.

BACKGROUND AND OBJECTIVES: Recombinant human growth hormone (rhGH) is approved for use in children with Turner’s syndrome (TS) in most industrialized countries and is recommended in the recently issued guidelines. We determined the growth responses of girls who are treated with rhGH for TS, with an aim to identify the predictors of growth response. MATERIALS AND METHODS: Fifty-six prepubertal girls with TS, documented by peripheral blood karyotype, were enrolled. All the patients received biosynthetic growth hormone therapy with a standard dose of 30 IU/m2/week. The calculated dose per week was divided for 6 days and given subcutaneously at night. RESULTS: This study showed that rhGH therapy provides satisfactory auxological results. Bone age delay is to be considered as a predictive factor which may negatively influence the effect of rhGH therapy on final height. The growth velocity in the preceding year is the most important predictor of rhGH therapy response. CONCLUSION: These observations help us to guide rhGH prescription, to reduce the risks and costs.

Evaluación de los niveles séricos de la proteína de unión de alta afinidad de la hormona de crecimiento humana (GHBP) y del polimorfismo del exón 3 del gen del receptor de GH en niños con talla baja idiopática / Evaluation of serum levels of the high affinity binding protein of human growth hormone (GHBP) and exon 3 polymorphism of the GH receptor gene in children with idiopathic short stature

La talla baja idiopática (TBI) incluye a un grupo heterogéneo de pacientes con fallas en su crecimiento. Una causa probable de TBI puede ser la insensibilidad a la GH (IGH). La proteína de unión de GH de alta afinidad (GHBP) se genera por el clivaje proteolítico de la porción extracelular del receptor de GH (GHR) y su determinación se propone como un marcador periférico del nivel de GHR en los tejidos. El objetivo de este trabajo fue evaluar los niveles de GHBP circulantes y su asociación con factores de crecimiento y el polimorfismo del exón 3 del gen GHR en niños con TBI. Los niños con TBI presentaron talla, IMC, IGF-I, IGFBP-3, ALS y niveles de GHBP significativamente más bajos que un grupo de niños de edad comparable (p<0.001). El genotipo del exón 3 del GHR no fue un factor determinante de las diferencias observadas. La máxima respuesta de GH de los tests de estímulo de secreción correlacionó negativa y significativamente con los niveles de GHBP (r= -0.28, p= 0.012). Los perfiles de distribución de la concentración de GHBP, IGF-I, ALS y BP3 expresadas en score de desvío estándar (SDE) en la TBI, mostraron un sesgo hacia niveles bajos. En conclusión, los marcadores de acción de GH y los niveles de GHBP fueron bajos en la TBI, independientemente del genotipo del exón 3 del gen GHR. En un subgrupo de niños con TBI, niveles disminuidos de GHBP y de componentes del sistema de los IGFs, colaborarían en la evaluación de la IGH sugiriendo la búsqueda de defectos en el GHR.

Idiopathic Short Stature (ISS) includes a heterogeneous group of children with growth failure. One possible explanation for the growth failure is a reduced responsiveness to growth hormone (GH). Human circulating GH is partially bound to a highaffinity binding protein (GHBP) which is derived from proteolytical cleavage of the extracellular domain of the GH receptor. Many reports have demonstrated a close relationship between GHBP and liver GH receptor status in physiological conditions and diseases. Moreover, serum GHBP measurement has been proposed as an useful peripheral index of GH receptor abundance. Our objective was the evaluation of serum GHBP levels and its probable association with serum growth factors (IGF-I, IGFBP-3 and ALS) and the exon 3 polymorphism of the extracellular domain of the GHR gene in ISS children. Children with ISS presented significantly lower height SDS, BMI SDS, serum components of the IGFs system and GHBP concentration as compared to an age-matched control group of normal children (p<0.001). Interestingly, exon 3 genotype did not influence the differences observed in these parameters. The maximal GH response obtained after two GH provocative tests inversely and significantly correlated to GHBP serum levels (r= -0.28, p= 0.012). A frequency study showed a deviation to low SDS values of serum GHBP, IGF-I, IGFBP-3 and ALS. Conclusion: 1- in children with ISS the exon 3 genotype of the GHR gene is not a factor that could explain the lower levels observed in circulating GHBP concentration and components of the IGFs system; 2- low serum GHBP together with low IGF-I, IGFBP-3 or ALS levels would help pointing to GH insensitivity due to GH receptor gene abnormalities in ISS.

Farmacogenética do tratamento com hormônio de crescimento (GH) em crianças com deficiência de GH / Growth hormone pharmacogenetics in children with growth hormone deficiency

O hormônio de crescimento (GH) recombinante humano (rhGH) é o único tratamento disponível para crianças com deficiência de GH (DGH). Embora os resultados sejam em média satisfatórios, existe uma ampla variabilidade individual, de forma que alguns indivíduos ainda falham em atingir uma estatura normal ou dentro do seu potencial genético, mesmo quando diagnosticados e tratados sob as mesmas recomendações. Parte dessa variabilidade tem sido atribuída à falta de individualização da dose, uma vez que a terapia é baseada em doses fixas de rhGH ajustadas somente pelo peso. As variáveis clínicas preditivas de resposta ao tratamento com rhGH conhecidas até o momento explicam apenas 50% da variabilidade observada, sugerindo que outros parâmetros preditivos ainda estejam por ser reconhecidos. Apesar do intenso progresso de estudos moleculares, variáveis genéticas envolvidas na modulação da capacidade de resposta ao tratamento com rhGH permanecem amplamente desconhecidas. Sendo assim, o objetivo do presente estudo foi avaliar a influência de variantes gênicas comuns, presentes em genes envolvidos nos mecanismos de ação do GH, sobre a capacidade de resposta de crescimento de crianças com DGH tratadas com rhGH, de forma a fornecer ferramentas para a individualização do tratamento. Quatro polimorfismos de importância funcional presentes em três genes envolvidos nos mecanismos de ação do GH foram correlacionados à capacidade de resposta ao tratamento com rhGH em 84 crianças pré-púberes com DGH. Os achados moleculares foram correlacionados com a velocidade de crescimento no primeiro ano (n=84) e com a altura ao final (n=37) após tratamento com rhGH. As análises estatísticas foram ajustadas para as demais variáveis clínicas relacionadas à resposta ao tratamento com rhGH. Três desses polimorfismos a presença (GHRfl) ou ausência (GHRd3) do exon 3 do gene do receptor de GH (GHR); as repetições (CA)n, da região promotora do gene do fator de crescimento insulina-símile...

Recombinant human growth hormone (rhGH) is the standard treatment for children with growth hormone deficiency (GHD). Although growth outcomes are usually satisfactory, there is a wide range of individual variability, so that some children do not achieve normal adult height or fail to reach final heights near their genetic potential, even when diagnosed and treated according to the same recommendation. Part of this variability has been attributed to the lack of treatment individualization, since therapy is based on fixed rhGH doses adjusted only by body weight. Clinical variables which predict growth responses to rhGH so far explain only 50% of the variability observed, suggesting that other influential factors may be missing from current prediction models. Despite the striking progress of molecular studies, genetic variables which are involved in modulation of rhGH responsiveness remain largely unknown. Thus, the aim of the present study was to evaluate the influence of common genetic variants present in genes involved in GH actions on the rhGH responsiveness of children with GHD. We assessed the influence of four functional polymorphisms in three genes involved in GH actions on treatment outcomes after rhGH treatment in 84 prepubertal children with GHD. Genotypes were correlated to first year growth velocity (n = 84) and final height after treatment (n = 37). Statistical analyses were adjusted for other clinical influential factors. Our results demonstrated that three of these polymorphisms the presence (GHRd3) or absence (GHRfl) of GH receptor (GHR) gene exon 3; the (CA)n repeats, in the insulin-like growth factor-1 (IGF1) promoter region; and the -202 A/C polymorphism, in the promoter region of insulin-like growth factor binding protein -3 (IGFBP3) gene can independently and interactively influence the rhGH responsiveness of children with GHD...

Investigação de baixa estatura: aspectos clínicos, laboratoriais e moleculares da insensibilidade ao hormônio de crescimento / Short stature investigation: clinical, laboratorial and genetic aspects concerning the trowth hormone insensitivity (GHI)

Neste artigo são descritos os aspectos clínicos, laboratoriais e genéticos da investigação da baixa estatura, dando ênfase para o diagnóstico da insensibilidade ao hormônio de crescimento (IGH). O paciente apresentado possuía características clínicas típicas de pacientes com IGH e em idade pré-púbere seus achados laboratoriais eram compatíveis com este diagnóstico (IGF-1 e IGFBP3 baixos, GH basal e pós-estímulo elevados). No entanto, quando avaliado durante a puberdade, as dosagens de IGF-1 e IGFBP-3 foram normais, dificultando o diagnóstico. O estudo molecular identificou mutação no exon 7 do gene do receptor do hormônio de crescimento (S226I). Discutiram-se os passos realizados para identificar a mutação e demonstrar que ela é responsável pelo fenótipo observado no paciente. Também será feita revisão dos casos de IGH descritos no Brasil e dos novos defeitos moleculares descritos nesta doença.

It is reported in this study the clinical, laboratory and genetic aspects of short stature investigation with emphasis to the diagnostic approach of growth hormone insensitivity (GHI). This patient in case presented typical clinical features of GHI and his laboratory findings at prepubertal age were typical of those observed in GHI patients (low IGF-1 and IGFBP-3 levels, with high basal and stimulated GH levels). However, during the puberty, he presented normal IGFBP-3 and IGF-1 levels that hindered the diagnosis. The molecular study disclosed a mutation in exon 7 of growth hormone receptor gene (S226I). The steps that demonstrated the causative effect of this mutation are shown here, and also a review of Brazilian GHI cases is given and new molecular defects in this field are discussed as well.