Osteoporosis is a disease which is characterized by the involution of the bone matrix. This is mainly due to the excessive activity of the osteoclasts (responsible for the bone resorption). Decreased density of bone tissue causes increased incidents of fractures. Fractures are most prominent in distal forearm (colles’ fracture), vertebral bodies and hip.
Osteoporosis can be divided into two categories,
1) type 1 (postmenopausal)
2) type 2 (age related)
Type 1- Occurs mainly in the post menopausal women. After the menopause, blood estrogen levels decrease. This fosters the development of osteoclasts and causes rapid decrease in the bone density.
Type 2- This occurs due to the age related decrease in the peak bone mass and associated with,
Impaired function of the senescent osteoblasts (associated with the deposition of the bone)
Increased PTH levels
In postmenopausal women activity of the osteoclasts can be decreased by the estrogen replacement therapy. (But this has questionable results and should be started only after a careful risk and benefit assessment.)
Increased intake of calcium and moderate exercise from the very young age may help to prevent osteoporosis.
Patients who are immobile and under glucocorticoid treatment are predisposed to osteoporosis. Patients with high circulating levels PTH due to primary or secondary hyperparathyroidism is also at risk.