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

摘要

There is clear evidence that human ageing is associated with reduced activity of the growth hormone(GH)/insulin-growth factor-I (IGF-I) axis, the so called “somatopause”. Although this condition is likely to contribute toage-related changes in body composition, structure functions and metabolism, we are now in face of the paradox oflifelong GH/IGF-I deficiency or resistance resulting in prolonged life expectancy. This evidence questions whether GHdeficiency is or is not a beneficial adaptation to ageing. On the other hand, neuroendocrine studies provided evidence thatbrain ageing is associated to peculiar age-related alterations in the control of GH/IGF-I axis, mostly including GHRHdeficiency and SS hyperactivity, reflecting the age-related cholinergic impairment. This hormonal pattern is present innormal and demented elderly subjects, and a neuroendocrine distinction among these conditions is impossible. Thisreview will focus on the age-related decline in the activity of GH/IGF-I axis as a function of either normal or pathologicalbrain ageing. Particularly, the influence of GH/IGF-I axis on cognitive functions and related disorders will be discussed.