Growth hormone receptor polymorphisms.

Many variables influence the outcome of growth hormone (GH) therapy (GH dose and duration, height - SDS at treatment start or at puberty onset, bone age, mid parental height, growth velocity, age, etc.). Nevertheless, all these factors only partially explain the interindividual variability in response to GH in GH deficiency (GHD) and in short non-GHD subjects. To this regard, genes coding for factors involved in GH action could play an important role. GH acts through the GH receptor (GHR), and therefore the GHR gene could be the first candidate to influence the response to GH. Polymorphisms of the GHR have been described in exons 3, 6 and 10. The first one consists in the deletion (d3) or retention (fl) of the entire exon 3. The d3 polymorphism has been recently associated with a better growth response to GH in idiopathic short stature subjects and in short children born small for gestational age. Subsequent studies on the same and other categories of short children (idiopathic short stature, small for gestational age, GHD, Turner syndrome) have reported controversial results, with some confirming the role of d3 and others showing no effect. This review analyses these studies trying to explain the apparent discrepancies, mainly due to different selection criteria and different dose regimens in treating GHD and non-GHD short subjects.