Unidade de Endocrinologia do Desenvolvimento, Laboratorio de Hormonios e Genetica Molecular, LIM/42, Disciplina de Endocrinologia, Hospital das Clinicas, Faculdade de Medicina da Universidade de São Paulo, São Paulo 05403-900, Brazil.
J Clin Endocrinol Metab. 2011 Sep;96(9):E1457-60. doi: 10.1210/jc.2011-0170. Epub 2011 Jun 29.
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.
The aim of this study was to identify mutations in GHRH in a large cohort of patients with IGHD.
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 peak GH after 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.
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.
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.
尽管已经有许多关于 GH1 和 GHRHR（生长激素释放激素受体）基因突变导致孤立性生长激素缺乏症（IGHD）的报道，但生长激素释放激素本身的突变尚未见报道，但却是生长激素缺乏症的明显候选原因。
本研究旨在鉴定 IGHD 大样本患者中的 GHRH 突变。
从国家和国际中心诊断为 IGHD 的 151 例患者中分离出 DNA。72 例患者满足以下所有标准：严重身材矮小（身高标准差评分≤-2.5）、刺激后 GH 峰值低（峰值≤5ng/ml）、正常后叶垂体和 GH1 和 GHRHR 突变缺失，因此是 GHRH 突变的强候选者。使用内含子引物通过 PCR 扩增 GHRH 的编码序列和剪接位点，并进行测序。
在 151 例患者中的 5 例（来自巴西的 42 例中的 4 例）中，发现 GHRH c.223 C>T，p.L75F 杂合突变。该变体先前被报道为一种多态性，在非洲人群中比在欧洲和亚洲人群中更为常见。在 5 例患者中鉴定出 6 种等位基因变异体（5 种新变异体），不预测氨基酸或剪接位点变化：c.147 C>T，p.S49S，IVS1-70 G>A，IVS1-74 T>C，IVS3-47 del1 和 IVS3+7 G>A/IVS3+41 G>A。在该队列中未发现功能突变。
在 IGHD 的选定患者队列中未发现 GHRH 突变，这表明如果存在，它们可能是 IGHD 的极罕见原因。在我们的队列中，其他尚未确定的遗传因素可能与 IGHD 的遗传病因有关。
