[Hormones and osteoporosis update. Insulin/IGF-I and bone].

Insulin and insulin-like growth factor-I (IGF-I) are potent bone anabolic factors through the balance of distinct signals of the two adaptor molecules, insulin receptor substrate (IRS) -1 and IRS-2 : IRS-1 for maintenance of bone turnover by up-regulating anabolic and catabolic functions of osteoblasts, while IRS-2 for retaining the predominance of the anabolic function over the catabolic function.