Growth hormone responses to varying doses of oral arginine.
Intravenous (IV) arginine invokes an increase in growth hormone (GH) concentrations, however, little is known about the impact of oral arginine ingestion on the GH response.


OBJECTIVE
The purpose of this study was to determine the dose of oral arginine that elicits an optimal GH response and to determine the time course of the response.


METHODS
Eight healthy males (18-33 years - 24.8+/-1.2 years) were studied on 4 separate occasions. Following an overnight fast at 0700 h, a catheter was placed in a forearm vein. Blood samples were taken every 10 min for 5 h. Thirty minutes after sampling was initiated, the subject ingested a dose of arginine (5, 9 or 13 g) or placebo (randomly assigned).


RESULTS
Mean resting GH values for the placebo, 5, 9 and 13 g day were 0.76, 0.67, 2.0 and 0.79 microg/L (n=6), respectively. Integrated area under the curve was not different with 13 g (197.8+/-65.7 min microg/L), yet it increased with 5 and 9 g compared with the placebo (301.5+/-74.6, 524.28+/-82.9 and 186.04+/-47.8 min microg/L, respectively, P<0.05). Mean peak GH levels were 2.9+/-0.69, 3.9+/-0.85, 6.4+/-1.3 and 4.73+/-1.27 microg/L on each day for the placebo, 5, 9 and 13 g days.


CONCLUSIONS
In conclusion, 5 and 9 g of oral arginine caused a significant GH response. A 13 g dose of arginine resulted in considerable gastrointestinal distress in most subjects without augmentation in the GH response. The rise in GH concentration started approximately 30 min after ingestion and peaked approximately 60 min post ingestion.
Collier
Scott R
SR
Department of Exercise Science, Syracuse University, 820 Comstock Avenue, Room 201, Syracuse, NY 13244, USA.
Casey
Darren P
DP
Kanaley
Jill A
JA
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology*; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D008297:Male
D019382:Human Growth Hormone; D001120:Arginine