A Simple Test for Growth Hormone Deficiency in Adults

GH deficiency (GHD) in adults is a well recognized clinical syndrome that results in significant metabolic and psychological morbidity. GH replacement therapy not only reverses these changes but improves the quality of life and results in a significant improvement in well being. There is no single simple and safe test to assess GHD. GHD in adults is diagnosed biochemically by provocative testing of GH secretion, and the insulin tolerance test (ITT) is accepted to be the test of choice. However, the ITT has many contraindications, needs multiple blood samples, and is potentially dangerous, requiring regular monitoring of patients in a specialized investigation unit. The aim of our study was to evaluate the GH-releasing effect of a combination of the hypothalamic secretagogue GHRH with a small dose of the synthetic peptide GHRP-2, to diagnose GHD. We have compared the GH response to ITT and GHRH/GHRP in a large group of adults with hypothalamic/pituitary disease (n = 36; 22 males and 14 females; age, 18 -59 yr) and in healthy volunteers (n = 30; 15 males and 15 females; age, 22-66 yr). The GHRH/GHRP test produces a measurable GH secretory response in normal, hypopituitary and GH-deficient patients. The test has no side effects. Using the ITT as our 'gold standard' with a GH response of 9 mU/L as our cut-off to define GHD, we compared the clinical efficacy of these two tests. Choosing an arbitrary cut-off of 17 mU/L to define GHD in the GHRH/GHRP test, this new test proved to have 78.6% sensitivity and 100% specificity even when we only used the 30-min datum point.