Age and gender are main determinants of senile osteoporosis. Do what extent are age-related endocrine changes involved? Traditionally androgens are considered to protect men against osteoporosis. Testosterone is indeed important for peak bone mass acquisition in men. The role of testosterone deficiency with respect to age- related bone loss is however less clear. In most of the recent large cohort studies men do not experience severe age-related testosterone deficiency. Testosterone deficiency may however be more prevalent with impact on bone in a subset of frail elderly men. Testosterone deficiency may also contribute in these men to muscle strength and risk of falls. Estradiol deficiency is the established cause of postmenopausal osteoporosis in women. Relative estradiol deficiency may also contribute to bone formation during puberty as well bone loss after puberty in men. Moreover, low estradiol concentrations are associated with fracture risk in men. Aging is also associated with an increase of sex hormone binding globulin in men. Sex hormone globulin has been linked to bone loss in elderly men. IGF-I levels are also associated with fracture risk as well as sex hormone binding globulin in elderly men. Finally age- related bone loss, fractures as well falls are associated with vitamin D deficiency as evaluated by serum 25 hydroxyvitamin D concentrations in both sexes. Serum 1.25 dihydroxyvitamin D3 however appear inversely related to bone density in elderly men. In conclusion, aging of bone/ muscle is a multifactorial process which appears to be affected by multiple endocrine changes such as estrogen, testosterone growth hormone as well as vitamin D. Differences in sex steroid concentrations during ageing as well during peak bone mass acquisition may explain some of the gender protection of men against osteoporosis.