 Osteoporosis is a major health problem in postmenopausal women. At age 50, half of women will suffer an osteoporotic fracture in their remaining lifetime, causing increased disability and mortality. Vitamin D deficiency, defined as a serum 25OHD 15 ngmL, contributes to osteoporosis via decreased calcium absorption CaAb, secondary hyperparathyroidism HPT, increased bone resorption and decreased bone mineral density BMD. Thus, experts agree that patients with vitamin D deficiency should receive vitamin D therapy. 