Brief Answer: Increased Resorption and Decreased Redeposition. Detailed Answer: Hello, I have gone through your query and understand your concern. Simply saying, in normal adults, 2 process takes place in bone. 1. Bone resorption - A small amount of bone minerals regularly and daily. 2. Bone redeposition- An equal deposition of new mineral in the bone. At old age, this balance between 2 process does not occur ie.. Bone resorption exceeds redeposition. Thus bones weaken (osteopenia) and over time can become brittle and prone to fracture (osteoporosis). There are plenty of factors which increases the risk of Osteoporosis are age, Inactive lifestyle, History of broken bones, Family history of osteoporosis, Low body weight and small thin frame, Menopause, Diet low in calcium and/or vitamin D, Smoking and Alcohol abuse, Steroid use etc. Thus old age itself is the main risk factor in developing Osteoporosis. As one reaches menopause, there is also estrogen deficiency, this lead to accelerated bone resorption. Also in old age, the function of intestine, kidney and skin are also decreases. This lead to decreased Vitamin D production by skin and decreased absorption of calcium by intestine and reabsorbtion by kidney. Further as one grow old, the bone forming cells called Osteoblasts and their activity also decreases. You have not mentioned about any symptoms or other reports for understanding and answering the query. I would be happy to help you if you want to discuss further.

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