Growth hormone receptor polymorphism and the effects of pegvisomant in acromegaly

Background: Sensitivity to pegvisomant therapy is highly variable in patients with acromegaly but determinants of this variability are still unknown. Lack of exon 3 (d3-) of the growth hormone (GH) receptor (GHR) has been associated with increased biological activity of GH. Objective: To assess whether the presence of d3-GHR haplotype may have a role in predicting dose regimen and response to pegvisomant in acromegaly. Design: Case series. Setting: Institutional referral center at a tertiary care hospital. Patients: Ninenteen acromegalic patients with active disease after unsuccessful neurosurgery and somatostatin analog therapy. Measurements: before and 1, 3, 6 and 12 months after treatment with pegvisomant, IGF-I; GH receptor genotype, determined from peripheral blood by polymerase chain reaction. All patients started treatment with pegvisomant at 10 mg/daily and then increased the dose, according to a fixed schedule, during a 12-month follow-up until normalization of IGF-I levels. Results: d3-GHR patients required a significant lower dose of pegvisomant and shorter treatment time to normalize IGF-I. Conclusion: the GHR genotype could be useful in predicting dose and individual response to pegvisomant in acromegaly.