Human Ageing and the Growth Hormone/Insulin-Like Growth Factor-I(GH/IGF-I) Axis - The Impact of Growth Factors on Dementia

Publisher Summary This chapter focuses on the age-related changes in the activity of the growth hormone/insulin-like growth factor-I (GH/IGF-I) axis as function of either normal or pathological brain aging. Particularly, the influence of the GH/IGF-I axis on cognitive functions and related disorders is considered along with its potential clinical implications. The strong influence of GH on body composition, metabolism, and structure functions, including central functions, is definitely demonstrated by how adult GHD patients benefit from rhGH replacement. Although somatopause is likely to contribute to age-related changes in body composition, structure functions, and metabolism, the paradox is lifelong GH/IGF-I deficiency or resistance, resulting in prolonged life expectancy and GH replacement at advanced age, probably exerting antiaging effects. However, neuroendocrine studies provides evidence that brain aging is associated with peculiar age-related alterations in the control of the GH/IGF-I axis, reflecting the age-related cholinergic impairment. This hormonal pattern is present in normal and demented elderly subjects and also in adults with Down syndrome; however, neuroendocrine distinction among these conditions is, at present, impossible.