Growth Hormone: A Physiological Fountain of Youth?

Abstract

During childhood and early adult life, growth hormone (GH), secreted by the anterior pituitary, is involved in the growth of bones and muscles and other organs as well. Aging is characterized by a decrease in muscle mass and bone strength and an increase in adipose, similar to the effects of pathological hyposecretion of GH in the young. Aging is also accompanied by a gradual decrease in the output of GH, like the drying of an internal fountain, until in the eighth decade of life, it is secreted at less than one-fifth of the youthful level. The GH hypothesis of aging posits that with the availability of human recombinant growth hormone and human recombinant insulin-like growth factor-I, which mediates most of the effects of GH, the GH hypothesis has become testable. Initial experiments involving short term administration of GH in a group of elderly men did indeed show modest improvement in lean body mass and adipose tissue. These studies are sometimes—and incorrectly—taken as proof of the correctness of...