The Difference Between Osteoporosis, Hyperparathyroidism, and Osteomalacia.
Other diseases can cause lessening in bone mass. Hyperparathyroidism and osteomalacia (rickets) both do. Hypocalcaemia (or hypocalcemia) is low serum calcium condition that is often co-morbid with these other diseases, and can by itself cause a loss in bone mass. In osteoporosis, however, the blood levels of calcium and phosphorus are in the normal range. In osteoporosis there is no increase in unmineralized osteoid, unlike in rickets.
The major features of osteoporosis as they present in the clinic are fragile bones and an increase in the rate of fracture. Under a microscope you can see the tiny changes in the bone tissue. Long columns of calcified structure in the bone include bony spicules, and in osteoporosis-afflicted bone, the spicules are thinner than normal. Some orthogonal joiners disappear, leading to a weaker overall structure. Transient osteoporosis of the hip is a rare form of osteoporosis that seems to have a separate etiology from most osteoporosis.
Bone, like other living tissue, is always being removed. The bony part (calcium compounds) are resorbed into the blood stream while new structure is formed. Why do bones lose mineral mass? Either the rate of resorption increases or the rate of deposition declines. Each happens in osteoporosis but in change in resorption rate is larger.
Genetics plays the biggest role in determining the risk of osteoporosis, but diet, exercise, and illness can also play factors. Calcium supplements have been shown to increase bone density in the short term, although it is not clear whether the effect persists after the supplements are stopped.
Arthritis
Osteoarthritis (also called degenerative disease) is the wearing down of joints. Literally the joint can wear out - overuse in sports or repetitive work can cause this condition. The cartilage goes away. Aging is the main cause, and pretty much everyone has some osteoarthritis by age 70. Rheumatoid arthritis is a different disease. It's an autoimmune disease that is thought to have genetic and environmental causes.
Cartilage is made of collagen (protein fibers), proteoglycans (fibers of proteins and sugars), and chondrocytes (living cells), as well as water.
The NIH Osteoporosis and Related Bone Diseases National Resource Center has a webpage about the difference between osteoporosis and arthritis here.
This NIH page also has information.
See also: osteoporosis and cancer.
Last updated: Nov 6, 2011
