Calcium and vitamin D deficiency increase age-related bone loss by causing secondary hyperparathyroidism. Reduced endogenous vitamin D synthesis exacerbates the problem of dietary deficiency and involves elderly people living in their own homes, who are just as much at risk as those living in institutionalized care. The effects of secondary hyperparathyroidism may be offset by hypercalcaemia of the increased bone turnover of immobility, which has a direct adverse effect on the skeleton causing osteoporosis. Active vitamin D analogues are effective in suppressing secondary hyperparathyroidism caused by vitamin D deficiency. However, simple deficiency is optimally treated with parent vitamin D, which has a greater safety margin than active vitamin D therapy (1,25 dihydroxyvitamin D), which requires close monitoring in the elderly.