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Pathophysiology, Prevention, and Treatment of Osteoporosis
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Posted on: 11/28/2007
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Osteoporosis, thinning of the bones, occurs in about 25 percent of all American Caucasians. Many more have low bone density and are at risk of developing osteoporosis.
Bones develop through modeling; they adapt according to the amount and type of stress to which they are subjected. This is done with the help of calcium, some hormones such as estrogen and androgens, vitamin D, parathyroid hormone, and growth factors. Bone mineral density peaks in young adulthood and begins to decline. How much and how quickly it declines depends on several factors.
The better the bone mass at the peak, the less dramatic the loss of density. According to the author, men usually lose bone at a rate of 0.3 percent per year and women at 0.5 percent per year. Once a woman reaches menopause, the rate rises to two to three percent per year for six to 10 years. After this, the rate of loss drops again to about 0.5 percent.
The author points out several factors that play an important role in bone density: vitamin D, parathyroid hormone, calcitonin, estrogen, glucocorticoids, and thyroid hormone.
Estrogen plays an important role early in life as well. If a girl misses several periods or has no menstruation at all, she may be losing bone mass every year rather than gaining it. This loss of bone mass cannot be recouped later on.
If a doctor suspects a patient may have osteoporosis, a thorough evaluation is necessary. This begins with a medical history and physical examination, followed by blood tests (to exclude other diseases), and imaging studies to examine the bones and their density. These include x-rays of the spine, a single-beam densitometry of the forearm, computed tomography scanning (CT scan) of the spine, and/or dual energy x-ray absorptiometry (DEXA). If necessary, a bone biopsy may also be needed.
Prevention of osteoporosis starts with lifestyle changes. These include eating a diet rich in calcium. Recommended daily allowances of calcium vary with age: 1000 mg per day for a healthy adult under the age of 65 years, and 1500 mg per day for women who are post-menopausal. Physical activity is important while children are growing for bone building; in adulthood, exercise can help maintain bone density. The author also mentions the use of hip protectors to help prevent hip fractures.
Medications may help reduce the risk of fractures. Supplements of calcium and vitamin D (500 to 1000 mg per day) may slow the rate of bone mass loss in the elderly who do not consume enough dietary calcium. A recent study showed that although vitamin D itself did not provide a reduction in fractures, vitamin D did help reduce risk if combined with calcium. Hormone replacement therapy (HRT) is also used. The author points out that several small studies have confirmed the efficacy of HRT in raising the BMD and reducing the risk of spinal fracture by 50 percent, while another study found a reduction of 37 percent in fractures of the vertebrae. The serious adverse effects of HRT do, however, limit the patients who may benefit.
Selective receptor modulators (SERMs) are medications that act like estrogen, but without some of the effects that estrogen has on other parts of the body. These are promising for osteoporosis management. As well, a drug class called bisphosphonates can reduce the chances of spinal fractures, as can supplementation with calcitonin. Finally, for some patients, injections of parathyroid hormone may help, as may the use of strontium.
The author concludes with the following recommendations for orthopedic surgeons who see patients with osteoporosis:
- counseling for women at risk
- counseling regarding dietary needs for bone strength and to avoid alcohol and tobacco
- recommending weigh-bearing exercises for bone and muscle strength
- BMD testing for women over 65 years
- BMD testing for women who are postmenopausal and who have had a fracture
- begin therapy in women who are considered to be at risk for osteoporosis
- consider osteoporosis treatment for postmenopausal women who have had a spinal or hip fracture
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References:
Pankaj Kumar. Osteoporosis: Current Concepts. In Journal of Orthopedics. December 2007. Vol. 4. No. 3.
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