Finally, in addition to producing improved metabolic effects, short-term use of GH produces a number of important clinical benefits in patients with catabolic illnesses. However, although certain effects of GH therapy, such as improved nitrogen balance and enhanced rates of protein synthesis, suggest that GH may be useful in the hospital setting, efficacy studies measuring infection rates, length of hospital stay, and mortality are needed to define who will most benefit from GH therapy. Because it is not known whether GH stimulates neoplastic growth, it should not be given to patients with malignant disorders. Potential side effects mandating cautious use of the hormone in diabetics and patients with a propensity toward fluid retention include hyperglycemia and enhanced sodium retention at the renal tubule. In addition, one study showed that cancer patients undergoing major surgery achieved a more rapid positive nitrogen balance if their diet was supplemented with 25 g of arginine daily, as compared with control patients receiving an isonitrogenous glycine supplement.
Arginine appears to enhance immune function in both animals and humans.
Peripheral blood lymphocytes from healthy human males demonstrated, in vitro, that increasing concentrations of arginine increased the activity of natural killer cells and lymphokine-activated killer cells. Supplemental parenteral or enteral arginine has been shown to stimulate secretion of GH, insulin, and prolactin in humans. This study suggests potentially beneficial roles for arginine supplementation in the elderly, who frequently have decreased T cell numbers and function and reduced serum IGF-1 levels. Another large randomized, double-blind, controlled study in which a tube feeding enriched with arginine, fish oil, nucleotides, and antioxidants was used showed that the median hospital stay was significantly shorter with the experimental formula. Further studies to define which specific nutrient additives were responsible for the observed immunologic, metabolic, and clinical effects are indicated.