Oral arginine-lysine does not increase growth hormone or insulin-like growth factor-I in old men.
BACKGROUND
Older adults tend to have reduced growth hormone (GH) secretion and insulin-like growth factor I (IGF-I) levels as well as changes in body composition which are partially reversed by GH injections. Arginine stimulates GH release, and lysine may amplify this response. We investigated whether oral arginine/lysine could be used to increase basal IGF-I and GH levels in non-obese old men (age 69 +/- 5 years; mean +/- SD) to values similar to those of untreated young men (age 26 +/- 4 years).


METHODS
Two groups of 8 healthy old men were treated with 3 g of arginine plus 3 g of lysine or with placebo capsules twice daily for 14 days. Before and on day 14 of each treatment GH levels were determined in blood samples taken at 20-minute intervals from 2000-0800 h, IGF-I was measured at 0800 h, and a 1 microgram/kg GHRH stimulation test was done.


RESULTS
At baseline, mean GH peak amplitude (p < .02) and serum IGF-I (p < .0001) were lower, whereas GHRH responses were similar, in old vs young men. Arginine/lysine did not significantly alter spontaneous or GHRH-stimulated GH levels, or serum IGF-I. Arginine absorption was age-independent. The correlation (p < .005) between measured increments in serum arginine and increases in serum GH after a single dose of arginine/lysine was similar in old and young groups.


CONCLUSIONS
Our data suggest that oral arginine/lysine is not a practical means of chronically enhancing GH secretion in old men.
Corpas
E
E
Gerontology Research Center, Baltimore, MD 21224.
Blackman
M R
MR
Roberson
R
R
Scholfield
D
D
Harman
S M
SM
D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D001120:Arginine / Q000008:administration & dosage* / Q000494:pharmacology; D004338:Drug Combinations; D013006:Growth Hormone / Q000097:blood*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008239:Lysine / Q000008:administration & dosage* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged
D004338:Drug Combinations; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine; D008239:Lysine