Endocrine Abstracts

The improvement of physical function and mobility in a continuously expanding elderly population emerges as high priority of medicine today. Muscle mass, strength and maximal exercise capacity are major determinant of physical function and all have been shown to decline with aging which may contribute to the increase incidence of frailty and disability observed in elderly men whereas the decline in exercise capacity may facilitate the accumulation of body fat and insulin resistance.

Muscle adaption to exercise seems to be modulated by anabolic circulating endocrine hormones and by autocrine/paracrine local growth factors, which are all load sensitive. GH, IGF1 and T are directly involved in muscle adaptation to exercise as promote muscle protein synthesis whereas T and a locally expressed IGF1 has been reported to activate muscle stem cells called satellite cells. While exercise improves physical function, elderly men fail to sustain an exercise program and a suitable program has yet to be established. GH/IGF1 axis function and T levels decline markedly with aging, which indeed may explain the blunted response of muscle adaptation to exercise observed in elderly men.

Several studies have reported that administration of T improves muscle function in health elderly men. Conversely, GH failed to improve physical function despite the amelioration of detrimental somatic changes of aging. There are evidence of synergistic anabolic action of GH and T and few studies that used this approach have reported greater efficacy. Future studies would need to assess the clinical applicability of these findings as gathering evidence support the indispensable role of endocrine function on physical function integrity.