Abstract
Osteoporosis is mainly treated with estrogen as the hormone replacement therapy in the United States and Europe. Intestinal calcium absorption is decreased in calcium deficiency in old age due to an impaired action of vitamin D and vitamin D derivatives that are capable of correcting these abnormalities (1, 2). Despite these facts, treatment with the metabolically active hormonal form of vitamin D has never been seriously considered as a candidate for an agent in hormone replacement therapy because of the conflicting results so far obtained on the effect of vitamin D derivatives on osteoporosis. In Japan, on the other hand, vitamin D has been most widely used for osteoporosis over the last 10 years, whereas scarcely any estrogen has been used. According to the 1990 Consensus Statement on Osteoporosis announced in Copenhagen, “The positive effect of 1,25-(OH)2 vitamin D3 and 1α-hydroxy vitamin D3 on fracture incidence disclosed in some studies in osteoporotic subjects may reflect promotion of calcium absorption, especially in the elderly and those on low calcium intake.” The discrepancy in the usefulness of vitamin D derivatives in different parts of the world may be explained, at least in part, by the various degrees of calcium and vitamin D deficiency in each area. As a step toward properly evaluating the usefulness of vitamin D derivatives in the treatment of osteoporosis, reports made so far on the effect of vitamin D derivatives in osteoporotics are reviewed for evaluation and analysis.
Intestinal Ca absorption decreases with advancing age, and such a decrease is especially pronounced in osteoporotics (3). The decrease in calcium absorption is associated with postmenopausal estrogen deficiency and may be corrected by estrogen administration (4).
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