Definition : It is reduction in bone tissue mass causing weakness of skeletal strength (G. osteon = bone, pros = pore, oisis = condition.)
1. Excessive resorption of Ca+2 from bones : It results from excessive resorption of calcium and phosphorus from the bone, which leads to vertical compression or crush fracture of the vertebrae.
2. Menopause and Ca+2 absorption : Osteoporosis occurs in postmenopausal women and elderly men. It may result from defective intestinal calcium absorption.
3. Environmental factors : Possible environmental factors include smoking, excessive drinking and decreased exercise. Osteoporosis is more common in women than in men, and in old than middle aged persons.
4. Sex hormones : Imbalances of some hormones, thryocalcitonin, parathormone etc also cause osteoporosis.
5. Vitamin D : Deficiency of vitamin D causes osteoporosis.