The Exon 3-Deleted Growth Hormone Receptor (d3GHR) Polymorphism - a Favorable Backdoor Mechanism for the GHR Function

Abstract

Growth hormone (GH) is a peptide hormone that plays a crucial role in controlling growth, development, and lifespan. Molecular regulation of GH is accomplished via the GH receptor (GHR) gene, which is the main factor influencing human development and is essential to optimal functioning of the GH/IGF-I axis. Two GHR isoforms have been studied, according to the presence (flGHR) or absence (d3GHR) of exon 3. The d3GHR variant, which has recently been related to longevity, is associated with enhanced signal transduction and higher receptor function. Many of these studies indicated that the growth response to GH treatment may be affected. Individuals carrying the d3GHR isoform have higher receptor activity, improved signal transduction, and alterations in the treatment response and efficacy compared with those carrying the WT isoform. Further, studies performed in patients with acromegaly, Prader-Willi syndrome, Turner syndrome, small for gestational age (SGA), and growth hormone deficiency (GHD) suggested that the d3GHR variant may have an impact on the relationship between GH and IGF-I levels, height, weight, BMI, and other variables. Other research, however, revealed inconsistent results, which might have been caused by confounding factors, including limited sample sizes and different experimental methods. In this review, we lay out the complexity of the GHR isoforms and provide an overview of the major pharmacogenetic research conducted on this ongoing and unresolved subject.