Pegvisomant interference in GH assays results in underestimation of GH levels

Introduction: Pegvisomant use in acromegaly negates the use of GH levels to monitor disease activity. To achieve antagonism, plasma concentrations must be ~1000-fold greater than GH which with the high homology between the peptides makes GH measurement a challenge when pegvisomant is present. Objective: We investigated the effect of pegvisomant on GH measured using commercially available assays. Methods: Pooled serum samples with GH concentrations Results: With baseline GH Conclusion: The presence of pegvisomant resulted in artefactually low measured GH in most assays. We speculate this fall is due to assay antibody-binding pegvisomant, reducing the amount of available antibody to bind actual GH thereby producing less sandwich formation: the ‘high-dose hook’ effect. In most assays, this effect is modest and results in lower GH, but the level of interference makes them unsuitable for studies on the influence of pegvisomant on GH neuroregulation.