Diagnosing and treating anterior pituitary hormone deficiency in pediatric patients.

Hypopituitarism, or the failure to secrete hormones produced by the anterior pituitary (adenohypophysis) and/or to release hormones from the posterior pituitary (neurohypophysis), can be congenital or acquired. When more than one pituitary hormone axis is impaired, the condition is known as combined pituitary hormone deficiency (CPHD). The deficiency may be primarily due to a hypothalamic or to a pituitary disorder, or concomitantly both, and has a negative impact on target organ function. This review focuses on the pathophysiology, diagnosis and management of anterior pituitary hormone deficiency in the pediatric age. Congenital hypopituitarism is generally due to genetic disorders and requires early medical attention. Exposure to toxicants or intrauterine infections should also be considered as potential etiologies. The molecular mechanisms underlying the fetal development of the hypothalamus and the pituitary are well characterized, and variants in the genes involved therein may explain the pathophysiology of congenital hypopituitarism: mutations in the genes expressed in the earliest stages are usually associated with syndromic forms whereas variants in genes involved in later stages of pituitary development result in non-syndromic forms with more specific hormone deficiencies. Tumors or lesions of the (peri)sellar region, cranial radiation therapy, traumatic brain injury and, more rarely, other inflammatory or infectious lesions represent the etiologies of acquired hypopituitarism. Hormone replacement is the general strategy, with critical periods of postnatal life requiring specific attention.

Nocturnal salivary cortisol is an accurate non-invasive test to assess endogenous hypercortisolism in children with obesity and a clinical phenotype suspicious for Cushing's syndrome.

INTRODUCTION: Cushing's syndrome (CS) constitutes one of the most challenging diagnostic assessments for paediatric endocrinologists. The clinical presentation of some children with exogenous obesity overlaps with those observed in hypercortisolism states. Accurate, non-invasive first-line tests are necessary to avoid false-positive results in the obese. We aimed to evaluate the diagnostic accuracy of salivary cortisol to assess endogenous hypercortisolism in children with obesity and clinical overlapping signs of Cushing's syndrome. METHODS: Case-control study that included children aged 2-18 years, BMI-SDS ≥ 2.0 and a follow-up >2 years. Patients were assigned to three categories: Group A, features strongly indicative of paediatric CS (growth failure combined with increasing weight); Group B, features suggestive of CS (e.g. moon face and striae); and Group C, less specific features overlapping with CS (e.g. hypertension, hirsutism, insulin resistance). Children in categories A and B formed the control group. Ten patients with confirmed CS were the case group. All children collected saliva samples on the same day in the morning between 7 to 8 am (morning salivary cortisol: mSC) and at 11 pm (nocturnal salivary cortisol: nSC). The mSC and nSC results were used to calculate the percentage decrease of cortisol at night (%D). Main outcomes by ROC for nSC and the %D were sensitivity, specificity, positive (P) and Negative (N) predictive values (PV) and their corresponding 95%IC. Salivary cortisol was measured by electrochemiluminiscence assay (lower limit of quantification: 2.0 nmol/L). RESULTS: 75/112 children met the inclusion criteria, whereas 22/75 children were eligible for the control group. Only controls decreased nSC [median and interquartile range: 2.0 (2.0-2.5) nmol/L] compared to mSC [6.9 (4.8-10.4) nmol/L], p< 0.0001. A cut-off for nSC ≥8 nmol/L confirmed CS within a sensitivity: 1.0 (0.69 to 1.0), specificity: 1.0 (0.85 to 1.0), PPV: 1.0 (0.69 to 0.99) and NPV: 1.0(0.85 to 0.99), achieving a diagnostic efficiency of 100%. The cut-off obtained for %D was 50%. No child with CS had a %D ≥50%, but 6/22 children in the control group had a %D below the cut-off, resulting in a lower overall diagnostic accuracy of 81% compared to nSC. CONCLUSION: Salivary cortisol at 11 pm is an accurate, feasible and non-invasive first-line test to assess endogenous hypercortisolism in children with obesity and clinical suspicion of Cushing's syndrome. The nSC was also useful in showing that the circadian rhythm of cortisol was preserved in children with exogenous obesity. In patients with nSC ≥8.0 nmol/L, other biochemical assessments and imaging studies are needed to further confirm the aetiology.

Sistema de la hormona de crecimiento y factores de crecimiento en niños y adolescentes / Growth hormone and growth factors system in children and adolescents

El crecimiento y la maduración física del niño y del adolescente transcurre por diversas etapas observándose cambios en la talla y velocidad de crecimiento característicos que son consecuencia entre otros factores, de cambios hormonales en el sistema o eje de la hormona de crecimiento (GH). Los principales componentes de este eje con utilidad clínica en la etapa infanto-juvenil son la GH, el factor de crecimiento insulino símil tipo I (IGF-I) y las proteínas de transporte. La GH es secretada por la hipófisis en forma de pulsos a la circulación y esto es uno de los principales factores que condicionan su utilidad como marcador de deficiencia de GH. La medición de GH en condiciones basales únicamente tiene valor diagnóstico cuando se obtiene en hipoglucemia y especialmente si se trata de un neonato. Es necesario entonces, en el resto de los casos, evaluar la capacidad de secreción de GH mediante pruebas funcionales de estímulo estandarizadas. Los factores dependientes de GH son considerados biomarcadores fidedignos de la acción de GH. Sin embargo, su concentración varía ampliamente durante la etapa pediátrica obligando su interpretación en el contexto de valores de referencia establecidos según la edad, sexo y desarrollo puberal. El presente trabajo revela los profundos cambios fisiológicos en los componentes del sistema de la GH que ocurren en la etapa pediátrica y los recaudos que deben tenerse en cuenta cuando se utilizan en el diagnóstico de la deficiencia de GH

Among other factors, the postnatal growth and physical maturation of children and adolescents (characterized by changes in the size and growth velocity rates) are influenced by components of the growth hormone (GH) system. GH, the type I insulin-like growth factor (IGF-I) and their transport proteins constitute the more relevant biochemical tools for the GH deficiency (GHD) diagnosis in pediatrics. The GH is secreted by the pituitary gland into the circulation in pulses and this pulsatility limits its usefulness, with the exception of a random basal GH in neonates under hypoglycaemia. Therefore, it is necessary to evaluate GH secretion status in standardized functional tests. IGF-I and IGFBP-3 are considered reliable biomarkers of GH action. However, these GH-dependant biomarkers widely vary in the paediatric period, forcing their interpretation in the context of confident reference values according to age, sex and pubertal development. The present revision reveals the profound physiological changes in the components of the GH system throughout the whole pediatric period and the situations that must be taken into account when they are used in the diagnosis of GHD

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.

El receptor de la hormona de crecimiento humana (hGH) y la proteína de transporte de alta afinidad de la hGH / Human Growth Hormone (GH) Receptor and the High Affinity GH-Binding Protein

La hormona de crecimiento humana (hGH) circula parcialmente unida a su proteína de transporte de alta afinidad (GHBP) la cual resulta del clivaje proteolítico del dominio extracelular del receptor de GH. Recientemente la enzima TACE se identificó como la metaloproteasa responsable del clivaje y liberación de GHBP a circulación. Aunque aún se desconoce la función específica de esta proteína de transporte, distintos trabajos en la literatura demuestran efectos que potencian y efectos inhibitorios sobre la acción de GH. Por otro lado, existen evidencias que demuestran una fuerte relación entre la GHBP y el nivel de receptor de GH en el hígado en situaciones fisiológicas y patológicas. Esto permitió proponer a la determinación de GHBP en suero como un marcador periférico de la abundancia del receptor de GH en los tejidos. La determinación de la concentración de GHBP sería de especial interés para evaluar pacientes con diagnóstico probable de insensibilidad a la acción de GH y orientar el posterior estudio de anormalidades en el gen del receptor de GH. En la presente revisión, también se abordan dificultades metodológicas relacionadas a la medición de GHBP sérica.

Human circulating growth hormone (GH) is partly bound to a high-affinity binding protein (GHBP) which is derived from proteolytical cleavage of the extracellular domain of the GH receptor. Recently, the metalloproteinase TACE has been identified as an important enzyme responsive for inducing GHBP shedding. Although the specific function of GHBP is not fully known, both enhancing and inhibitory roles of this binding protein on GH action have been proposed. Many reports have demonstrated a close relationship between GHBP and the liver GH receptor status in physiological conditions and diseases. Moreover, serum GHBP measurement has been proposed as an useful peripheral index of the GH receptor abundance. Related to the latter, circulating GHBP concentration would be of special interest for the evaluation of GH insensitivity due to GH receptor gene abnormalities. In addition, the present review also focus on methodological problems concerning serum GHBP measurement.