Osteoporosis is a condition in which bone mass, and therefore, bone strength, is decreased. This results in an increased risk of fracture. Primary osteoporosis occurs due to normal, predictable changes within the body during the aging process. Secondary osteoporosis occurs as a result of some other specific disease process that produces osteoporosis as one of its symptoms.

To understand osteoporosis, it is helpful to understand the basics of bone formation. Bone is formed on a protein base (collagen) by the deposition of minerals, particularly calcium. This laying down of bone is carried out by specialized cells called osteoblasts. The formation of new bone occurs most effectively along lines of stress/weight that are experienced by the bone. Other cells, osteoclasts, are responsible for reabsorbing (taking up) bone. These cells actually digest already-formed bone.

This active reabsorbtion-formation cycle within bone occurs throughout life, so that old bone is always...