Pegvisomant-primed glucagon stimulation test in assessing GH reserve and GH/IGF kinetics in adults suspected of GH deficiency

Purpose: The accuracy of the glucagon stimulation test (GST) in diagnosing adult GH deficiency (GHD) has recently been questioned. Because pegvisomant (PegV) increases endogenous GH secretion, we hypothesized that priming PegV to the GST (PegV-GST) 72 h beforehand would improve the diagnostic accuracy of this test. This pilot study aimed to prospectively compare PegV-GST to two other diagnostic tests for adult GHD. Methods: Adults suspected of GHD underwent PegV-GST, GST and insulin tolerance test (ITT) in random order. Growth hormone levels (measured by a PegV insensitive assay) during PegV-GST, GST and ITT were compared, and acute effects of PegV on GH/IGF kinetics were assessed. Results: Ten subjects with hypothalamic-pituitary disease and 1–4 pituitary hormone deficiencies were studied. Basal and peak GH levels with the PegV-GST were comparable to those of the GST and ITT. The five subjects that failed the GST and ITT were the same subjects that failed the PegV-GST, using the peak GH cutpoint of