osteoporosis (ŏs´tēō´pərō´sĬs), disorder in which the normal replenishment of old bone tissue is severely disrupted, resulting in weakened bones and increased risk of fracture; osteopenia results when bone-mass loss is significant but not as severe as in osteoporosis. Although osteoporosis can occur in anyone, it is most common in thin white women after menopause.

Bone mass is typically at its greatest during a person's mid-twenties; after that point there is a gradual reduction in bone mass as bone is not replenished as quickly as it is resorbed. In postmenopausal women the production of estrogen, a hormone that helps maintain the levels of calcium and other minerals necessary for normal bone regeneration, drops off dramatically, resulting in an accelerated loss of bone mass of up to 3% per year over a period of five to seven years. Smoking, excessive alcohol consumption, and a sedentary lifestyle increase the risk of bone-mass loss; a diet high in protein and sodium also speed calcium loss. The disorder also has a genetic component. A vitamin D receptor gene that affects calcium uptake and bone density has been identified, and the different forms of this gene appear to correlate with differences in levels of bone density among osteoporosis patients.

Osteoporosis has no early symptoms and is usually not diagnosed until a fracture occurs, typically in the hip, spine, or wrist. A diagnostic bone density test is thus recommended as a preventive measure for women at high risk. Treatment can slow the process or prevent further bone loss. Estrogen replacement therapy for postmenopausal women is effective but has potential side effects. Calcitonin, a thyroid hormone, is administered in some cases. Nonhormonal drugs for the treatment of osteoporosis include alendronate (Fosamax) and risedronate (Actonel), bisphosphonates that decrease bone resorption, and raloxifene (Evista), a selective estrogen receptor modulator that can increase bone mineral density. Teriparatide (Forteo), which consists of the biologically active region of human parathyroid hormone, stimulates the activity of osteoblasts, the specialized cells that form new bone. Dietary and supplemental calcium and vitamin D are usually recommended for people at risk, but a seven-year study of more than 36,000 women over 50 that was released in 2006 found that supplements conferred little benefit. Exercise, including weight training, has been found to strengthen bones directly and to improve muscle strength and balance and thus minimize the chance of falls.

See M. Hegsted, Advances in Nutrition Research, Vol. 9: Nutrition and Osteoporosis (1994).

The Columbia Encyclopedia, 6th ed. Copyright© 2016, The Columbia University Press.

Osteoporosis: Selected full-text books and articles

Primary Care of the Older Adult: A Multidisciplinary Approach By Mary M. Burke; Joy A. Laramie Mosby, 2000
Librarian’s tip: Chap. 11 "Osteoporosis"
Arthritis: A Take Care of Yourself Health Guide for Understanding Your Arthritis By James F. Fries Perseus Books, 1999 (5th edition)
Librarian’s tip: Chap. 12 "Osteoporosis: Brittle Bones"
The Evolving Female: A Life-History Perspective By Mary Ellen Morbeck; Alison Galloway; Adrienne L. Zihlman Princeton University Press, 1997
Librarian’s tip: Chap. 10 "The Cost of Reproduction and the Evolution of Postmenopausal Osteoporosis"
Natural Menopause: The Complete Guide By Susan Perry; Kate O'Hanlan Perseus Books, 1997 (Revised edition)
Librarian’s tip: Chap. 6 "Understanding Osteoporosis"
Debating Biology: Sociological Reflections on Health, Medicine, and Society By Simon J. Williams; Lynda Birke; Gillian A. Bendelow Routledge, 2003
Librarian’s tip: Chap. 16 "A Normal Biological Process? Brittle Bones, HRT, and the Patient-Doctor Encounter"
Beyond the 120-Year Diet: How to Double Your Vital Years By Roy L. Walford Four Walls Eight Windows, 2000 (Revised edition)
Librarian’s tip: "Osteoporosis" begins on p. 131
Selling Sickness: How the Drug Companies Are Turning Us All into Patients By Ray Moynihan; Alan Cassels Allen & Unwin, 2005
Librarian’s tip: Chap. 8 "Testing the Markets: Osteoporosis"
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