A practical approach to the diagnosis of growth hormone (GH) deficiency in patients transitioning to adulthood using GH stimulation testing.

To establish the diagnosis of adult growth hormone deficiency (GHD), GH-deficient children transitioning to adulthood are evaluated by two separate stimuli 2 or more weeks after ceasing GH therapy. While 20-88% of children diagnosed with idiopathic GHD retest with normal values, those with proven genetic defects in GH production/secretion/bioactivity and patients with panhypopituitarism consistently test deficient. The US Food and Drug Administration (FDA) defines GHD in adults by stimulated peak serum GH concentrations <5 ng/ml if measured by polyclonal radioimmunoassays (RIA) or lower if measured by monoclonal assays. Some investigators define severe GHD by a peak GH concentration <3 ng/ml. Adult responses to arginine and glucagon testing are similar to the responses to insulin tolerance testing; clonidine, pyridostigmine, and galanin cause lesser peaks of GH. Growth hormone-releasing hormone (GHRH) combined with arginine, GH releasing peptide-6 (GHRP-6), or hexarelin leads to higher peak responses than GHRH alone. Thus the choice of testing methods impacts the diagnosis of GHD in transition patients.