689 resultados para GHRH-récepteur


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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Context: Although numerous reports of mutations in GH1 and GHRHR (GHRH receptor) causing isolated GH deficiency (IGHD) have been published, mutations in GHRH itself have not been hitherto reported but are obvious candidates for GH deficiency. Objective: The aim of this study was to identify mutations in GHRH in a large cohort of patients with IGHD. Patients and Methods: DNA was isolated from 151 patients diagnosed with IGHD at national and international centers. Seventy-two patients fulfilled all the following criteria: severe short stature (height SD score <= -2.5), low peakGHafter stimulation (peak <= 5 ng/ml), eutopic posterior pituitary lobe, and absence of mutations in GH1 and GHRHR and therefore were strong candidates for GHRH mutations. The coding sequence and splice sites of GHRH were amplified by PCR with intronic primers and sequenced. Results: In five of 151 patients (four of 42 from Brazil), the GHRH c. 223 C>T, p. L75F change was identified in heterozygosity. This variant has been previously reported as a polymorphism and is more frequent in African than European and Asian populations. Six allelic variants (five novel) that do not predict change of amino acids or splice sites were identified in five patients: c. 147 C>T, p.S49S, IVS1 -70 G>A, IVS1 -74 T>C, IVS3 -47 del1, and IVS3 +7 G>A/IVS3 + 41 G>A. No functional mutations were found in this cohort. Conclusions: GHRH mutations were not identified in a selected cohort of patients with IGHD, suggesting that, if they exist, they may be an extremely rare cause of IGHD. Other, as-yet-unidentified genetic factors may be implicated in the genetic etiology of IGHD in our cohort. (J Clin Endocrinol Metab 96: E1457-E1460, 2011)

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Growth hormone (GH) influences bone mass maintenance. However, the consequences of lifetime isolated GH deficiency (IGHD) on bone are not well established. We assessed the bone status and the effect of 6 months of GH replacement in GH-naive adults with IGHD due to a homozygous mutation of the GH-releasing hormone (GHRH)-receptor gene (GHRHR). We studied 20 individuals (10 men) with IGHD at baseline, after 6 months of depot GH treatment, and 6 and 12 months after discontinuation of GH. Quantitative ultrasound (QUS) of the heel was performed and serum osteocalcin (OC) and C-terminal cross-linking telopeptide of type I collagen (ICTP) were measured. QUS was also performed at baseline and 12 months later in a group of 20 normal control individuals (CO), who did not receive GH treatment. At baseline, the IGHD group had a lower T-score on QUS than CO (-1.15 +/- 0.9 vs. -0.07 +/- 0.9, P < 0.001). GH treatment improved this parameter, with improvement persisting for 12 months post-treatment (T-score for IGHD = -0.59 +/- 0.9, P < 0.05). GH also caused an increase in serum OC (baseline vs. pGH, P < 0.001) and ICTP (baseline vs. pGH, P < 0.01). The increase in OC was more marked during treatment and its reduction was slower after GH discontinuation than in ICTP. These data suggest that lifetime severe IGHD is associated with significant reduction in QUS parameters, which are partially reversed by short-term depot GH treatment. The treatment induces a biochemical pattern of bone anabolism that persists for at least 6 months after treatment discontinuation.