Genetic characterization of growth hormone 1 gene in patients with isolated growth hormone deficiency

Growth hormone (GH) secretion and release is a complex and highly regulated process. Any alteration disturbing synthesis, secretion or biological action of GH, results into growth hormone deficiency (GHD). GHD is of two types-isolated growth hormone deficiency (IGHD) and combined pituitary hormone deficiency (CPHD), of which IGHDis more common. The genes implicated in its etiology are growth hormone 1(GH1) and receptor of growth hormone-releasing hormone (GHRHR). Mutations within the coding region and/or either entire or partial deletions of the GH1gene lead to IGHD. In addition, GH1 possesses upstream regulatory elements and a promoter with binding sites for various transcription factors, which control its expression.

The study was planned with an aim to identify entire GH1 locus deletion, mutations in the GH1 coding region and sequence variations (polymorphisms) in the promoter region of the gene in patients with IGHD.

Thirty patients clinically diagnosed with IGHD and 30 healthy individuals who formed the controls were enrolled for the study. Genomic DNA was isolated from peripheral blood sample and processed for amplification of the desired regions followed by direct sequencing and/or restriction endonuclease digestion.

Out of the 30 IGHD patients screened, 20% of the cases showed consanguinity and 16% had a positive family history. Seven percentage of the patients showed homozygous deletion of the GH1gene while rest of them had heterozygous deletion. Screening of the coding region of GH1 showed sequence variations in exon 1 in 20% of the patients whereas the promoter region showed the presence of polymorphisms-rs2005171 in 20%, rs2005172 in 15% and rs11568828 in 18% of the cases. The haplotype comprising rs2005171 and rs2005172 was observed in four patients.

The present study is an attempt to characterize the GH1 locus in IGHD patients. To the best of our knowledge this is the first study of its kind where entire GH1locus, upstream regulatory elements and promoter region have been studied. Such an analysis would provide valuable information on the etiology of IGHD.