The IGF1 response to recombinant human growth hormone (rhGH) showed some individual variability and the responsible factors for this behavior remain unknown. Some studies have emphasized the possible role of isoforms of the GH receptor (GHR), showing conflicting results.
Therefore, we investigated the possible influence of the isoforms of the GHR to the diagnosis of GHD and in determining adult hormone replacement therapy responsiveness.
We studied 69 patients with GHD (M: 37, F: 32, mean age 40.9, median age 41) treated with rhGH using an identical standardized protocol in a single centre, with a duration of follow-up (median) up to 60 months.
We have observed that there is no significant difference in terms of IGF1 and GH peak at diagnosis of GHD, while the presence of the d3-GHR in homozygosity is related to a significant increase in IGF1 levels at 6 and 12 months of therapy; main determinants of the increase of IGF1 at both 6 and 12 months appear to be the dose of rhGH, the patients age at diagnosis and the genotype of the GH receptor. No differences between genotypes were found in the long-term follow-up.
GHR isoforms seem to affect the IGF1 response to rhGH in short term follow-up, but further prospective studies will clarify whether this hypothesis may have a predominant role in the variability of patient response to hormone replacement therapy.