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 potential alternatives to GH as therapeutic agents. There is wide interest in the possibility that elevating GH and IGF-I might increase muscle mass, physical strength and performance, and possible sleep and cognition in aging. The GH secretagogs, like GH, can produce a sustained stimulation of this axis; in contrast to GH, they preserve feedback regulation at the pituitary level and stimulate a near-physiologic pulsatile pattern of GH release. GHRP's and their nonpeptide analogs are also active when given orally, a significant practical advantage. Short-term 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 promote sleep; and that these agents are generally well tolerated. Longer-term studies assessing effects upon body composition and physical and psychological function are underway.
Merriam
G R
GR
VA Puget Sound Health Care System, American Lake Division, Tacoma, WA 98493, USA. merriam@u.washington.edu
Buchner
D M
DM
Prinz
P N
PN
Schwartz
R S
RS
Vitiello
M V
MV
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000187:drug effects* / Q000502:physiology; D005069:Evaluation Studies as Topic; D016330:Frail Elderly; D013006:Growth Hormone / Q000031:analogs & derivatives / Q000187:drug effects* / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000627:therapeutic use*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000187:drug effects / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000187:drug effects / Q000378:metabolism; D009842:Oligopeptides / Q000627:therapeutic use*
D018972:Insulin-Like Growth Factor Binding Protein 3; D009842:Oligopeptides; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone