Age-Related Decreases in Growth Hormone and Insulin-Like Growth Factor (IGF)–1: Implications for Brain Aging

There is abundant empirical and scientific evidence to support the hypothesis that functional deterioration of tissue with age is closely related to a decline in hormone concentrations and/or hormone action, but the specific etiology and/or consequences of these deficiencies remain elusive. Growth hormone (GH) and insulin-like growth factor–1 (IGF-1) are two potent anabolic hormones that decrease with age, and contribute to the loss in tissue function associated with normal aging. In this review, (1) basic age-related changes in the regulation of these hormones are detailed and information related to mechanisms of tissue resistance to GH are presented; (2) the potential use of GH as a therapeutic intervention to delay physiological changes associated with age is discussed; and (3) current information on the relationship among GH, IGF-1, microvascular rarefaction, and brain aging is detailed. Finally, our findings of beneficial actions of GH and IGF-1 are reconciled with other investigators using dwarf mod...