What is osteoporosis?
Osteoporosis is a disorder of the bones characterized by a progressive loss of bone tissue, with a resulting increase in the risk of bone fractures. Normal bone is composed of a framework made of protein (called collagen) and calcium salts. Osteoporosis depletes both the calcium salts and the protein in the bone. The bone then becomes weaker and is more prone to breakage (fracture), either by cracking or collapsing (compression). Bone fracture in osteoporosis can occur with only a minor fall or injury that normally would not cause a bone fracture.
Normal bone has two layers. The outer layer, called the "cortical bone", is very dense and compact. The inner layer, called the "trabecular bone," is far less compact than the cortical bone, and has a honeycomb structure. The bones of the spine (vertebrae) are mainly composed of trabecular bone, while bones of the neck of the hip bone (femur) are mostly made of cortical bone. Different types of osteoporosis affect different proportion of trabecular and cortical bone. In postmenopause osteoporosis, the spine is more commonly affected than the hip. In contrast, in senile (due to aging) osteoporosis, both cortical and trabecular bones are affected. Osteoporosis leads to bone fractures. Fractures of the spine cause loss of height due to compression of the vertebrae (the building blocks of the spine).
Over 20 million people have osteoporosis in the United States, and approximately 1.3 million people each year will suffer a broken bone as a result of osteoporosis. The osteoporosis process can operate silently for decades. The patients may not be aware of their brittle osteoporotic bones until suffering a fracture. In 1993, the United States incurred an estimated loss of 10 billion dollars due to loss of productivity and health care costs related to osteoporosis.
What factors determine bone mass?
Bone mass (or bone density) is the amount of bone present in the skeletal structure. The higher the bone mass and density, the stronger the bones. Bone mass is primarily determined by genetic factors. Men have a higher bone mass than women. Black Americans have a higher bone mass than white or Asian Americans. A vitamin D receptor gene has been found in the human chromosomes that regulates bone mass. Adequate dietary intake of calcium and physical exercise can increase bone mass.
Normally, bone mass is accumulated during childhood and reaches a peak by age 25. Bone mass is then maintained for ten years. After age 35, both men and women will lose 0.3-0.5% of their bone mass per year as part of the normal aging process.
Estrogen is important in maintaining bone mass, especially in the trabecular bone of the spine. When estrogen levels drop after menopause, bone loss accelerates. During the first five to ten years after menopause, women can suffer up to two to four percent loss of trabecular bone mass per year! This can result in the loss of up to 25-30% of their trabecular bone mass during that time period. Accelerated bone loss after menopause is a major cause of osteoporosis in women.
What are the risk factors for osteoporosis?
Many factors will increase the risk of developing osteoporosis. These factors are related to genetics, life style, hormones, and certain medications. Genetic factors include female gender, Caucasian or Asian race, thin and small body frames, and a family history of osteoporosis.
Life style risk factors include cigarette smoking, excessive alcohol and caffeine consumption, lack of exercise, and a diet low in calcium.
Hormone related risk factors include menopause, early surgical removal of both ovaries, a pituitary gland tumor in the brain, hyperthyroidism (the presence of too much thyroid hormone), hyperparathyoidism (the presence of too much parathyroid hormone), and a lack of vitamin D.
Low estrogen levels caused by menopause or surgical removal of both ovaries can lead to osteoporosis in women. Similarly, low testosterone levels in men can also cause osteoporosis. Tumors of the pituitary gland in the brain can cause a reduction in the production of estrogen. They can also release excessive amounts of a hormone, called prolactin, which can cause osteoporosis.
Hyperthyroidism, a condition wherein too much thyroid hormone is produced by the thyroid gland (as in Grave's disease), can cause osteoporosis. Osteoporosis can also result from taking too much thyroid hormone medication.
Hyperparathyroidism is a disease wherein there is excessive parathyroid hormone production by the parathyroid gland. Normally, the parathyroid hormone maintains blood calcium levels by, in part, removing calcium from the bone. In untreated hyperparathyroidism, excessive parathyroid hormone causes too much calcium to be removed from the bone, which can lead to osteoporosis.
Vitamin D helps the body absorb calcium. When vitamin D is lacking, the body cannot absorb adequate amounts of calcium to prevent osteoporosis. Vitamin D deficiency can result from lack of intestinal absorption as in celiac sprue and in primary biliary cirrhosis. In celiac sprue, the damaged small bowel lining cannot absorb vitamin D. In primary biliary cirrhosis, insufficient bile from the liver prevents the absorption of vitamin D.
Certain common medications can cause osteoporosis. These include heparin (a blood thinner), anti-seizure medications phenytoin (DILANTIN) and phenobarbital. Corticosteroids (such as PREDNISONE) are used for many conditions such as asthma, rheumatoid arthritis, and ulcerative colitis. When administered over long periods of time, corticosteroids can cause osteoporosis.
What are the symptoms of osteoporosis?
Patients with osteoporosis generally have no symptoms until bone fractures occur. Fractures of the spinal vertebrae are usually a result of the compression of bone (vertebral compression fractures). Spine vertebral fractures can occur without pain. However, they can often cause a severe "band-like" pain that radiates around from the spine to both sides of the body. Over many years, the spinal fractures cause a loss of height of the spine resulting in the person becoming shorter. A curvature of the spine can also occur, giving the individual a hunched-back appearance. This can lead to chronic backaches.
Fractures of the other bones in the body can cause severe pain at the site of the fracture. The trauma causing the fracture can be relatively minor. When fracture occurs during the "stress" of normal activity, it is called a stress fracture. For example, some patients with osteoporosis can develop stress fractures of the feet while walking or stepping off a curb.
Hip fractures usually occur as a result of a fall. Since the bone can become so weakened in osteoporosis, hip fractures can occur with trivial accidents. Hip fractures in the elderly can lead to other medical complications. The weak, osteoporotic bone may be difficult to heal after surgical repair of the fracture. Pneumonia and blood clots in the leg veins that can travel to the lungs (pulmonary embolism) can complicate hip fracture recovery due to prolonged bed rest. Aggressive physical therapy after repair of the hip fracture can decrease these complications. Despite these measures, up to 30% of patients will require long-term nursing home care following a hip fracture.
How is osteoporosis diagnosed?
A routine x-ray examination can reveal osteoporotic bones, which appear much thinner and lighter than normal bones. Unfortunately, by the time x-rays can detect osteoporosis, at least 30% of the bone mass has already been lost.
Bone densitometry can be used to calculate the bone density and can detect osteoporosis earlier than routine x-rays. There are several ways to perform bone densitometry. Computerized tomography or CT scans are useful in evaluating the spine. Single photon absorptiometry (SPA) typically evaluates bone mass in the forearm and is fairly precise in gauging bone loss. The best technique currently available in measuring bone mass is dual energy x-ray absorptiometry (DEXA). DEXA measures bone mass in the hip and the spine. The test takes only 5-10 minutes to perform, uses very little radiation (less than one tenth the amount used on a standard chest x-ray), and is quite precise. DEXA can also be used repeatedly over a period of time to follow changes in bone density.
How is osteoporosis treated?
The best treatment for osteoporosis is prevention. Quitting smoking and curtailing alcohol intake are helpful. Exercise against gravity can reduce bone loss and can even stimulate new bone formation. Additionally, exercise increases agility, strength, and endurance; factors that can reduce accidents. Exercise programs are individualized and should be regular; at least several times weekly. For patients with underlying musculoskeletal disorders, combining exercising with joint protection techniques is important.
Calcium supplements are useful, especially in women. Average women in the United States receive less than 500 milligrams of calcium per day in their diet. The recommended daily allowance (RDA) of calcium intake is 800mg per day. The National Institute of Health Consensus Conference on Osteoporosis has recommended a calcium intake for postmenopausal women of 1000mg per day if they are also taking estrogen and 1500mg per day if they are not taking estrogen.
Estrogen replacement in postmenopausal women is important in the prevention of accelerated bone loss. Estrogen can even reverse the bone loss that occurs after menopause. Estrogen is available orally (PREMARIN) or as a skin patch (ESTRADERM). Women with certain conditions, such as a history of breast cancer, phlebitis, or stroke may not be candidates for estrogen because of the potential for worsening or inducing recurrences of these conditions.
Calcitonin (CALCIMAR) is a drug that is FDA approved for the treatment of postmenopausal osteoporosis. Calcitonin is a natural hormone that slows the rate of bone loss. Calcitonin increases bone density and can occasionally relieve bone pain. Common side effects of calcitonin include nausea and flushing. Calcitonin can be given by an injection under the skin every other day. Recently, a nasal spray form of calcitonin (MIACALCIN) has become available. Nasal sprays seem to have fewer side effects than injectable calcitonin.
Etidronate (DIDRONEL) is a drug that increases bone density and decreases the rate of recurrence of fractures in patients with osteoporosis. It currently is not FDA approved for the treatment of osteoporosis, but is approved for use in another bone disorder called Paget's disease. Despite its lack of FDA approval for use in osteoporosis, it has been used extensively over the past few years to treat osteoporosis.
Alendronate (FOSAMAX) is a new medication that has recently been approved by the FDA for the treatment of postmenopausal osteoporosis. Alendronate decreases the accelerated rate of bone loss that occurs after menopause. It has been shown to increase lumbar spine bone density by 10% and hip bone density by 6%. Alendronate is taken in the morning, on an empty stomach thirty minutes before breakfast, with a glass of water. Side effects are usually mild, but can include upset stomach. Alendronate is chemically referred to as a biphosphonate drug. Other biphosphonates are being studied for both postmenopausal and cortisone-induced osteoporosis. These include risedronate for which preliminary studies are encouraging.
Vitamin D supplementation has been shown to be of benefit in elderly patients, particularly those in nursing homes. This is probably due to the fact that many patients in nursing homes are vitamin D deficient.
Medications that are undergoing testing for osteoporosis include sodium flouride and parathyroid hormone. Flouride appears to decrease the incidence of fractures and increase bone density. Parathyroid hormone given daily in low dosages appears to significantly increase bone density.
As the population of the United States continues to age, the number of people with osteoporosis and subsequent fractures will increase exponentially. The pain, suffering, and economic costs will be enormous. It is vitally important for people to become aware of osteoporosis and its prevention and treatment to limit its impact. With continued research, there will hopefully be even better and more effective treatment options for osteoporosis.
Good Sources of
Information provided by MedicineNet Used here with permission.
The materials and information on this server are intended for educational and informational purposes only. The materials and information are not intended to replace the services of a trained health professional or to be a substitute for medical advice of physicians and/or other health care professionals. The International Still's Disease Foundation is not engaged in rendering medical or professional medical services. You should consult your physician on specific medical questions, particularly in matters requiring diagnosis or medical attention. The International Still's Disease Foundation makes no representations or warranties with respect to any treatment, action, application medication or preparation by any person following the information offered or provided within this website. Any information used from other websites was done so with permission from each site, with an exception to those of "public domain", whereas we believe any site without a cited reference was a "public domain site" and for our use. The International Still's Disease Foundation is a non-profit organization. This page was last updated on January 17, 2001
Copyrightę 1999-2001 International Still's Disease Foundation