POTENTIAL APPLICATIONS OF GH SECRETAGOGS IN THE EVALUATION AND TREATMENT OF THE AGE-RELATED DECLINE IN GROWTH-HORMONE SECRETION

The two classes of GH secretagogs-GH-releasing hormone (GHRH) and the GH-releasing peptides and their analogs (GHRP's)-retain their ability to endogenous GH secretion in healthy and frail elderly subjects. They have very limited utility in assessment of the state of the GH/IGF-I axis except to confirm an intact pituitary, but they are attractive po tential alternatives to GH as therapeutic agents. There is wide intere st in the possibility that elevating GH and IGF-I might increase muscl e mass, physical strength and performance, and possibly sleep and cogn ition in aging, The GH secretagogs, like CH, can produce a sustained s timulation of this axis; in contrast to GH, they preserve feedback reg ulation at the pituitary level and stimulate a near-physiologic pulsat ile pattern of GH release. GHRP's and their nonpeptide analogs are als o active when given orally, a significant practical advantage. Short-t erm treatment studies have shown that GHRH and the GHRP's can enhance GH secretion and elevate IGF-I and IGFBP-3 levels; that GHRH may promo te sleep; and that these agents are generally well tolerated, Longer-t erm studies assessing effects upon body composition and physical and p sychological function are underway.