Healthy bones are maintained by vitamin D, calcium and sex hormones. Calcium is the major component of bone that confers strength. Low calcium can lead to osteoporosis. In osteoporosis, there is disruption of the architectural framework of bone, which weakens bone. There is increased likelihood for fractures in osteoporosis. Adequate intake of calcium and vitamin D is necessary to slow down or prevent osteoporosis.
How Calcium is Regulated
The absorption of calcium from the intestines is facilitated by vitamin D. Calcium is regulated by the parathyroid and thyroid glands. These glands produce parathyroid hormone and calcitonin, respectively. Low blood calcium stimulates the parathyroid gland to produce parathyroid hormone, which acts on bone, causing it to break down and thereby release calcium into the bloodstream. Excess parathyroid hormone further complicates an already weak bone. The thyroid gland produces calcitonin in response to elevated calcium in the blood; calcitonin causes the removal of calcium from the blood.
Osteoporosis can occur due to low blood calcium or due to increased breakdown of bone. Diseases that lead to osteoporosis prevent the use of calcium in maintaining bone. It's important to maintain both adequate intake of calcium and the intake of vitamin D, since vitamin D is needed for calcium absorption.
Risk Factors
The risk for osteoporosis increases with advanced age in both men and women. The female sex is also a risk factor for osteoporosis. In women, the sex hormone estrogen becomes deficient in menopause, leading to a rapid loss in bone strength; in males, a drop in the male sex hormone testosterone has less effect on bone.
Excess alcohol and smoking are major risk factors for osteoporosis that can be avoided. Other risk factors include vitamin D deficiency and malnutrition. Being physically inactive can also cause a major loss in bone strength.
Associated Signs and Symptoms
Osteoporosis has no specific symptom but is associated with bone fractures that occur without significant stress on bone. Fractures can occur anywhere throughout the body. A fracture that occurs in the back can affect posture and reduce mobility. Fracture of a long bone, such as in the thigh, is a serious complication that requires surgery.
Elderly persons have an increased risk of falling, and osteoporosis increases the likelihood of fractures associated with falls.
Methods of Prevention
Osteoporosis can be prevented by making lifestyle changes. Quitting smoking and drinking are big steps in preventing osteoporosis. Bone weakens with advancement of age but regular exercise such as walking and jogging slows down the loss in bone strength. Exercise should be at least 30 minutes a day at least four days per week. Proper dietary intake of vitamin D and calcium can prevent osteoporosis. Diet should include intake of fish, eggs, vitamin D-fortified milk and cod liver oil; these are abundant sources of vitamin D. Vitamin D is synthesized under the skin in direct sunlight. Adequate sunlight exposure helps to prevent osteoporosis.
Treatment
Bisphosphonates such as sodium alendronate (Fosamax), risedronate (Actonel) or ibandronate (Boniva) are preferred treatments for confirmed osteoporosis. These drugs are very effective in reducing the risk of fracture. Oral bisphosphonates must be taken on an empty stomach. Bisphosphonates are not found over the counter; they must be prescribed by a physician.
Estrogen is important in maintaining normal bone density in women. Post-menopausal women are unable to make estrogen, thereby increasing their risk for osteoporosis; in these women, estrogen replacement is effective in preventing osteoporosis.
Vitamin D and calcium must be used in conjunction with other treatment modalities, since studies have not consistently demonstrated their effectiveness in preventing osteoporotic fractures. Vitamin D should be supplemented at doses of 400 to 600 international units, or IUs, per day; calcium should be supplemented at doses of 500 to 1,200 mg per day.
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