Can Growth Hormone Prevent Aging?

Abstract

Does growth hormone prevent aging? An article by Rudman et al. that appeared in the Journal in 1990 1 reported the effect on body composition of administering human growth hormone for six months to 12 older men. This article incited a proliferation of "antiaging" clinics and lay publications, such as "Grow Young with HGH," extolling the benefits of growth hormone in reversing or preventing aging. There are several Web sites that attempt to sell various oral and inhaled formulations of growth hormone; none of these formulations have been shown to be efficacious. In fact, since growth hormone is a peptide subject to degradation by gastric acid, oral preparations would not be expected to be effective. Other Web sites are selling oral formulations (branched-chain amino acids) that are claimed to release growth hormone. These oral formulations are based on studies of intravenous arginine. Intravenous arginine increases serum concentrations of growth hormone transiently (for less than one hour). The effect of oral branched-chain amino acids is akin to that of eating a steak. Clinical medicine is practiced on the basis of established evidence regarding outcomes. What is the evidence supporting the use of growth hormone to prevent aging? First, it is necessary to recall exactly what the study by Rudman et al. demonstrated. Twelve healthy men, 61 to 81 years of age, who had serum concentrations of insulin-like growth factor I below those found in normal young men received growth hormone for six months. (Insulin-like growth factor I mediates the action of growth hormone, and its concentration reflects the circulating concentration of growth hormone.) The weekly dose of growth hormone was approximately twice as high as the dose used in adult men with a growth hormone deficiency. The administration of growth hormone in older men resulted in a 4.7-kg increase in lean body mass, a 3.5-kg decrease in adipose mass, and an increase of 0.02 g per square centimeter in lumbar-spine density; systolic blood pressure and the fasting glucose concentration increased significantly. The study was not double-blind (there was a control group consisting of nine men who received no treatment); there were no assessments of muscle strength, exercise endurance, or quality of life. This study is the basis for claims that growth hormone reverses aging. My editorial accompanying the article by Rudman et al.2 concluded that such studies in older adults "should be viewed as an important beginning," with the implication that subsequent studies would determine the benefits and risks of growth hormone treatment in older adults.