Age-related changes in growth hormone secretion: Should the somatopause betreated?

Growth hormone (GH) secretion declines progressively with aging, and many a ge-related changes resemble those of the adult GH deficiency (GHD) syndrome , including a decrease in lean body mass; an increase in body fat, especial ly in the visceral/abdominal compartment; adverse changes in lipoproteins; and a reduction in aerobic capacity. The increase in central obesity can fu rther inhibit GH secretion. GPI replacement is effective in reversing many of these changes in adult GHD, and GH is now FDA approved for treatment of adults with documented GHD or hypopituitarism, although there is still only limited experience with its long-term benefits, side effects, and risks. T his early experience with GHD has led to speculation that replacing GH or s timulating its secretion may also be beneficial in normal aging, and to wid espread off-label use of GH in this context; however, there are still very few well controlled studies of the effects and side effects of GH or GH sec retagogues in aging. All published studies are of 6 months or shorter treat ment periods. From this limited experience there is a consensus that GH has effects on body composition, but reports disagree on effects on psychologi cal or physical functional performance. Older adults are much more suscepti ble to the dose-related side effects of GH, including peripheral edema, car pal tunnel syndrome, and a variable decrease in insulin sensitivity; and it is not known whether chronic GH treatment affects the risk of malignancy o r has other long-term risks. Thus while short-term results are somewhat enc ouraging, the evidence on risks and clinically pertinent benefits is still lacking to support the use of GH in normal aging outside of clinical studie s. Ln evaluating patients with clinical features suggesting GHD, which can be quite nonspecific, it is important to assess the presence or absence of true GH deficiency by the context (pituitary disease or its treatment, chil dhood GHD) and by appropriate GH stimulation tests before considering GH re placement.