Menopause and age-related

reduction MK-1775 in vivo of estrogen levels in women may also impact muscle strength because estrogen is converted to testosterone, which has an anabolic effect on muscle protein synthesis. Further, both sex hormones may suppress inflammatory cytokines that exert catabolic effects on muscle. Thus, hormone replacement has always received considerable interest as a therapy for sarcopenia. In women, trials of estrogen and testosterone therapy have failed to yield any meaningful increases of muscle strength [96]. Studies of testosterone replacement therapy in men has had mixed results, depending on age of the subjects. Several studies have shown that administration of testosterone in hypogonadal younger men produced significant increases in lean body mass and muscle strength [97–99]. Strength increases ranged from 20% to 60% but tended to be smaller than the increases produced by resistive exercise training. selleck kinase inhibitor Anabolic effects of testosterone therapy on older hypogonadal men tend to be weaker,

with most studies reporting minimal changes in body composition and no increases in muscle strength [96]. However, some studies have reported moderate strength improvements ranging from 10% to 25%, but unlike the negative results, all of these trials lacked control groups. However, it should be noted that testosterone is administered to older men in much lower doses than to younger men because of increased risk of prostate cancer and other side effects [96]. Considerable interest has also been devoted to testing the effect of GH on sarcopenia. Growth hormone exerts an Protein Tyrosine Kinase inhibitor indirect anabolic effect on muscle by stimulating production of IGF-1 in the liver. Levels of growth hormone are systematically lower in the elderly, and thus it was hypothesized that GH would be effective in combating muscle loss in elderly subjects. However, most studies Pregnenolone have shown

that GH treatment is ineffective in the elderly, both from the standpoint of muscle mass and muscle strength. The failure of GH treatment to augment muscle strength in elderly subjects has led to other approaches, such as treatment with growth-hormone-releasing hormone, which was found to increase GH production and produce moderate increases in muscle strength [96–100]. Additionally, others have tried direct administration of IGF-1. By complexing IGF-1 to its primary circulating binding protein IGFBP-3, it is possible to significantly increase the IGF-1 dose while eliminating the side effect of hypoglycemia that occurs with IGF-1 alone [101]. Boonen et al.