Screening of GHSR, GHRHR, GH1 genes in isolated growth hormone deficiency disease in Egyptian patients

Abstract

Isolated growth hormone deficiency (IGHD) is a hereditary disorder that causes significant short stature. GHD has a reported incidence of 1/4000–1/10,000 births. It is caused by mutations in the major somatotroph axis genes, involving GH1, codes for growth hormone, GHSR, and GHRHR, codes for growth hormone secretagogue receptor and growth hormone-releasing hormone receptor, respectively. The present study aims to examine the clinical phenotype and investigate the genetic etiology of ten Egyptian patients with type I isolated growth hormone insufficiency. Patients recruited for the study were clinically diagnosed by two provocation tests and were subjected to a thorough history, clinical examination, and anthropometric measurements. Sanger sequencing and mutational analysis of the three genes, GH1, GHSR, and GHRHR, was our approach, performed in all enrolled IGHD patients. The variants identified were analyzed using the biological, population, sequence variants, and clinical genetics databases. Prediction of the pathogenicity of the novel variants was done by in silico prediction tools following the American College of Medical Genetics and Genomics (ACMG) guidelines. Sanger sequencing revealed a previously reported pathogenic mutation (NM_000823.4: c.1069C > T; p.Arg357Cys) in the GHRHR gene in one patient and a novel frameshift variant (NM_198407.2: c.1043dup; Ser349Leu fs*6) in the GHSR gene in another patient. This is the fourth report highlighting the autosomal dominant inheritance of the GHSR mutation as a cause of isolated growth hormone deficiency. A number of previously reported variants, but of rare frequency, were identified in this study. In our IGHD cases, 90% of the patients were underweight, 50% had anemia, and 80% showed hypovitaminosis D. Our findings broaden the mutational spectrum underlying the IGHD in Egyptian patients and point out the importance of mutation screening of the GHSR and GHRHR genes. This study also acknowledges the autosomal dominant mode of inheritance of the GHSR mutation as a cause for dwarfism.