Osteoporosis: Cause, Diagnosis and Treatment
Osteoporosis is a skeletal disorder characterized by bone strength loss leading to fragility fractures.
i. optimal strength if the skeleton not achieved during growth and development of bones
ii. Rate of bone resorption is greater than the deposition during bone remodelling
iii. Failure to replace the lose bone material
iv. Oestrogen, calcium, calcitonin and Vitamin D deficiency
v. Age related and post menopausal
Pathogenesis of Osteoporosis
i. Increased osteoclast activity
The osteoclast occupies the Howship lacunae (caused by the erosion of bone by the osteoclast enzymes) in the trabeculae during bone remodelling. This induces the bone erosion when there is increased osteoclast activity compared to osteoblast activity.
ii. Role of vitamin D, calcitonin and parathyroid hormones
Vitamin D helps in absorption of calcium from intestine which is deposited in the bone with the help of calcitonin during bone development and parathyroid (PTH) extracts the calcium from bone to blood. They together act to maintain the blood calcium level normal Therefore, decreased Vitamin D, Calcitonin and calcium level or increased PTH level will induced the removal of calcium from bone to blood.
iii. Role of estrogen
Estrogen help to maintain the optimal blood calcium level by promoting it's absorption from intestine as well as by inhibiting it's elimination by kidney. In estrogen deficiency, the blood calcium depletes that activates the PTH, followed by the removal of calcium from the bone. The receptor activator of nuclear factor-$\kappa \beta$ ligand (RANKL) is activated by estrogen following T cell activation and TNF-$\alpha$ activation by estrogen. RANKL belongs to the tumour necrosis factor (TNF) super family and capable of activating the osteoclast generation that plays major role in bone erosion. In post menopausal women the estrogen level is depleted and this further induces the osteoporosis.
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