Concomitant, specific determination of growth hormone and pegvisomant in human serum

Growth hormone (GH) and the GH receptor blocker, pegvisomant are usually circulating in high concentration in pegvisomant treated acromegalic patients. This and the close similarity between the peptides make determination of either difficult. In the present methodological study, endogenous GH in serum is initially isolated and determined in a slightly modified commercial immunometric assay, whereafter the now GH free medium allows measurement of pegvisomant. Inter-individual steady state levels of serum pegvisomant vary remarkably in both acromegalic patients and healthy controls, while the intra-individual variations are negligible.