Influence of the Exon 3-Deleted/Full-Length Growth Hormone (GH) Receptor Polymorphism on the Response to GH Replacement Therapy in Adults with Severe GH Deficiency

Abstract

There is considerable individual variation in the clinical response to GH replacement therapy in GH deficient (GHD) adults. Useful predictors of treatment response are lacking. The aim of the study was to assess the influence of the exon 3-deleted (d3-GHR) and full-length (fl-GHR) GH receptor isoforms on the response to GH replacement therapy in adults with severe GHD. A total of 124 adult GHD patients (79 men; median age, 50 yr) were studied before and after 12 months of GH therapy. GHD patients were divided into those bearing fl/fl alleles (group 1) and those bearing at least one d3-GHR allele (group 2), and the genotype was related to the effects of GH therapy on IGF-I levels and total body fat (BF). GH dose was individually titrated to obtain normal serum IGF-I levels. GHR genotype was determined by PCR amplification, IGF-I levels by immunoassay, and BF by a four-compartment model. Seventy-two (58%) patients had fl/fl genotype and were classified as group 1, whereas 52 (42%) had at least one d3-GHR allele and were classified as group 2 (40 were heterozygous and 12 were homozygous). At baseline, there were no significant differences in the study groups. Changes in IGF-I and BF after 12 months of GH treatment did not differ significantly between the two genotype groups. The presence of d3-GHR allele did not influence the response to GH replacement therapy in our cohort of adults with severe GHD.