Does growth hormone prevent aging in the healthy elderly with low serum insulin-like growth factor-I ?

Aging is associated with a gradual decline in the function of a number of endocrine glands. While there are phenotypic similarities seen in the changes of aging with some endocrine hormone deficiency states, the relationship between the decline in growth hormone (GH) secretion, and the decrease in serum insulin-like growth factor-I (IGF-I), with these body composition changes is far from clear. The decline in serum IGF-I, unlike that of thyroxine and estradiol, is not accompanied by an increase in pituitary GH secretion. The recent enthusiastic recommendation for GH 'replacement' in the aging population with low serum IGF-I remains highly controversial. The evidence is still unclear on any significant beneficial effect of such replacement in healthy fit elderly men and women. There is some early evidence of beneficial effects of such replacement in the frail elderly. There are no studies that have investigated the effect of GH on longevity in humans, but results from animal studies on caloric restriction and longevity do not suggest that GH administration will increase life span. There is still insufficient evidence that treatment with exogenous GH in the healthy elderly that attains serum IGF-I levels similar to that of young adults is beneficial or safe.