ORNITHINE INGESTION AND GROWTH-HORMONE RELEASE IN BODYBUILDERS

Amino acid supplements are popular among bodybuilders because of unproven, yet attractive claims that pharmacologic dosages can elicit the release of growth hormone, an anabolic substance. Three female and nine male bodybuilders in training served as subjects. After an overnight fast, subjects were administered 40, 100 or 170 mg·kg-1 L-ornithine hydrochloride by mouth (oral route) in a random fashion over three successive Saturdays. Blood samples were drawn at baseline (T=0), 45 and 90 minutes post-administration. Regardless of dosage, mean 45 and 90 minute values for serum ornithine level were significantly (p<0.01) greater than baseline (T=0) values. Mean serum growth hormone levels tended to rise with ornithine ingestion, but only rose significantly (p<0.05) at 90 minutes post-administration at the 170 mg·kg-1 dosage. The findings indicate that oral ornithine is absorbed and systemic blood levels rise as a direct function of intake level. However, only at the highest dosage did ornithine elicit a predictable rise in serum growth hormone level. © 1990 Pergamon Press plc.