Osteoporosis
Osteoporosis
, bone condition characterized by a decrease in mass, resulting in bones that are more porous and more easily fractured than normal bones. Fractures of the wrist, spine, and hip are most common; however, all bones can be affected. White females are the most susceptible, but other risk factors include low calcium intake; inadequate physical activity; certain drugs, such as corticosteroids, (see Corticosteroids); and a family history of the disease. This explanation is given as part of SLE symptoms.The most common form of the disease, primary osteoporosis, includes postmenopausal (see Menopause), or estrogen-deficient, osteoporosis (Type I), which is observed in women whose ovaries have ceased to produce the hormone estrogen; age-related osteoporosis (Type II), which affects those over the age of 70; and idiopathic osteoporosis, a rare disorder of unknown cause that affects premenopausal women and men who are middle-aged or younger. Secondary osteoporosis may be caused by bone disuse as a result of paralysis or other conditions, including weightlessness in space; endocrine and nutritional disorders, including anorexia nervosa; specific disease processes; and certain drug therapies.
Recent research has shown that the development of osteoporosis is also related to a gene that determines the type of vitamin D receptor (VDR) a person inherits. The VDR gene exists in two forms, one of which produces a receptor that stores calcium more efficiently than the other. People who inherit two copies of the more efficient VDR gene develop high bone densities. Those who inherit two copies of the less efficient gene have somewhat less strong bones.
Prevention and treatment of osteoporosis include synthetic estrogen or progestin therapy or both for postmenopausal women, intake of calcium and other nutrients, weight-bearing exercise, and drugs such as calcitonin and alendronate sodium, a nonhormonal treatment for osteoporosis. In December 1997 a new synthetic estrogen called raloxifene was approved for treating osteoporosis. Like other estrogen therapies, raloxifene increases bone density, but with fewer side effects than earlier types of synthetic estrogen.
