Associated hormonal decline in aging: is there a role for GH therapy in aging men?

Aging is associated with decline in the somatotroph axis, a decline that has been considered to cause many of the catabolic sequelae of normal aging. Consequently, IGF-I levels decline progressively: this mainly reflects the impaired GH secretion, but decline in gonadal sex steroids and malnutrition also play a role. Decreases in GH secretion may partially explain the age-related changes in metabolism, bones, muscles, cardiovascular system, central nervous system, the immune system and sense of well-being. Normal aging and GH deficiency (GHD) share several clinical signs and symptoms: the endocrine pattern of aging is, however, distinct from the decrease of GH and/or IGF-I levels associated with hypopituitarism. Owing to clinical similarities between aging and GHD, the relative GH insufficiency of elderly subjects has been postulated as one important factor contributing to their frailty. However, it is currently unclear whether treatment with exogenous GH, or IGF-I can retard or reverse age-related changes in body structure and function. Several studies enrolling healthy elderly subjects showed that GH treatment was followed by increase of lean mass, decrease of fat mass and improvement of bone turnover, but other studies failed to confirm these data. The treatment with natural or synthetic GH secretagogues, that could represent a physiological approach to restore the GH and IGF-I secretion, requires further investigations. In conclusion, there is not sufficient evidence for a clear therapeutic role of rhGH, IGF-I, and secretagogues in aging. Further studies are needed to evaluate the real benefit of somatotropic treatment in aging men.