The National Institute of Arthritis, Musculoskeletal and Skin Diseases states that more than 10 million Americans suffer from osteoporosis, or brittle bone disease. Bone remodeling occurs continuously, as new bone tissue replaces old bone tissue. With osteoporosis, the rate of bone loss outpaces the production of new bone, weakening the internal structure of bones and raising the risk of fractures. Multiple factors contribute to the likelihood of developing osteoporosis.
Low Peak Bone Mass
According to the Mayo Clinic, bone mass peaks at around the age of 30. Higher peak bone mass lowers the odds that patients will develop osteoporosis as they age. The National Institute of Arthritis, Musculoskeletal and Skin Diseases explains that weight-bearing activities like running, dancing or weight-lifting help to build strong bones because bone, like muscle, is living tissue that strengthens in response to exercise. The Mayo Clinic says that a sedentary life-style increases the risk for osteoporosis.
A diet rich in bone-building vitamin and minerals, especially vitamin D and calcium, proves critical to building and maintaining bone mass. Vitamin D-rich foods include liver, salt-water fish and egg yolks. Exposure to sunlight, for as little as 15 minutes a day, can stimulate the body to produce sufficient levels of its own vitamin D. The need for calcium varies and peaks at ages 9 to 18. Pregnant, breast-feeding and post-menopausal women and older men need between 1000 to 1200 mg/day of calcium to retain strong bones, according to the National Institute of Arthritis, Musculoskeletal and Skin Diseases.
Bone Loss
Cells called osteoclasts ("bone-breakers") remove minerals from bone and chemically degrade bone components during remodeling. Their counter-parts, the bone building cells called osteoblasts, deposit calcium and produce collagen, the major structural component of bone. Osteoporosis can occur because of osteoclast hyperactivity or because of sluggish osteoblast activity. Scientists have identified some of the factors that can tip the balance towards bone loss.
As outlined by Drs. Rifas and Weitzmann in the November 2009 issue of "Arthritis and Rheumatology", immune factors called cytokines stimulate the production of osteoclasts, increasing the pace of bone loss. In that same issue, Dr. Dalle Carbonare and colleagues found that patients with osteoporosis have differences in mesenchymal stem cells, the parent cells of osteoblasts, which can limit their production.
Hormone Levels
The Mayo Clinic outlines the role of hormones in osteoporosis. Bone loss accelerates as levels of estrogen fall, particularly at menopause. In older men, low levels of estrogen and testosterone increase the risk of osteoporosis. People with a hyperactive thyroid gland; hyperthyroidism, or people on thyroid replacement drugs for low thyroid function; hypothyroidism, are more likely to develop osteoporosis because high levels of thyroid hormone deplete bones. Diseases that increase the levels of the adrenal hormone cortisol or use of corticosteroid medications also increase the rate of bone loss, raising the risk of osteoporosis.
References
- National Institute of Arthritis, Musculoskeletal and Skin Diseases: Osteoporosis
- Mayo Clinic.com: Osteoporosis
- Arthritis and Rheumatology; "A novel T cell cytokine, secreted osteoclastogenic factor of activated T cells, induces osteoclast formation in a RANKL-independent manner"; L. Rifas and M. Weitzmann; November 2009.
- Arthritis and Rheumatology; "Circulating mesenchymal stem cells with abnormal osteogenic differentiation in patients with osteoporosis"; L. Dalle Carbonare et al.; November 2009.
