Objective: The aim of this investigation was to study the effect of relatively high dose IGF-I therapy given for several months, on serum levels of IGF-I, IGF-II and IGFBP-3, and on IGF-I pharmacokinetics in patients with growth hormone insensitivity due to GH receptor dysfunction.
Design and patients: Two adolescent subjects from Ecuador were treated with recombinant IGF-I at a dosage of 120 micrograms/kg s.c. twice daily, in combination with a GnRH analogue for 8 months.
Measurements: Serum was sampled at baseline and at 3-8 months, for determination of IGF-I, IGF-II and IGFBP-3 by radioimmunoassay, and for evaluation of IGFBPs and IGFBP-3 protease activity by Western ligand blot and protease assay, respectively.
Results: Peak serum IGF-I levels ranged from 272 to 492 micrograms/l. Mean serum IGF-II levels were decreased concurrently with the increase in IGF-I. Serum IGFBP-3 levels failed to rise with prolonged IGF-I treatment. There was no apparent change in the half-life of IGF-I during the treatment period.
Conclusions: IGF-I administration does not increase serum levels of IGFBP-3 or significantly alter IGF-I pharmacokinetics.