Osteoporosis

Osteoporosis (porous bone) is a condition in which there is loss of bone mass (density) and bone tissue deteriorates. Bones become weak, brittle, fragile and can break easily. The bones most at risk for breaking because of osteoporosis include those in the hip, spine, wrist and leg.

Bone is a living tissue. There are two main types of bone cells that work together to form and shape bone. Osteoblasts make bone and osteoclasts dissolve it. Bone also contains minerals, such as calcium, that make bones hard and dense. The body needs enough calcium and other minerals and hormones to maintain bone density and strength.

Bone is constantly being renewed as old bone is removed and replaced by new bone, especially until we reach about age 30. This is when our bones are their strongest. Then, as part of the aging process, bones slowly decrease in density and bone is broken down faster than new bone can be formed.

Incidence

One in 4 Canadian women and one in 8 Canadian men over the age of 50 has osteoporosis, but the disease can occur at any age. The prevalence of osteoporosis is expected to rise because of our growing and aging population.

Risk factors

There are many risk factors for osteoporosis and bone fractures:

• low bone mineral density
• a history of fractures
  • A break in the bone that happens because the bone is too weak to stand any type of force is called a fragility fracture (or osteoporotic fracture). Having a fragility fracture after age 40 can increase the risk for another one.
  • A family history of fragility hip fracture, especially in a parent, can signal a risk for osteoporosis.
• increasing age
  • The older someone is, the greater the risk of osteoporosis. The greatest risk is in people 65 years of age or older.
• a tendency to fall
  • People with osteoporosis have a higher risk of fractures if they also have a tendency to fall or are at risk for falling. Some medications can cause drowsiness and increase the risk of falling, especially in the elderly.
• early menopause
  • Women who go through menopause early (before age 45) are especially at risk for osteoporosis because of the important role that estrogen plays in keeping bones healthy.
  • A woman's estrogen levels decline during menopause and she can lose bone tissue more quickly.
• certain types of cancer treatments
  • Long-term corticosteroid use (for more than 3 months), as a cancer treatment or to treat lung conditions associated with cancer or its treatment, can increase the risk of osteoporosis.
  • Some hormonal therapies that are used to block or decrease the body's production of certain hormones (estrogen or testosterone, for example) can increase the risk of osteoporosis. These hormones are thought to cause some cancers (breast or prostate cancer) to grow, but they also play a role in maintaining strong bones. Hormonal therapies that lower the levels of these hormones, such as aromatase inhibitors and luteinizing hormone–releasing hormone (LHRH) agonists, can increase bone loss.
  • Cancer treatments that cause early (premature) menopause, by stopping normal ovarian function and decreasing estrogen levels, contribute to loss of bone density. These treatments may include surgery to remove both ovaries (oophorectomy), chemotherapy drugs and radiation therapy to the pelvis.
  • Some anticonvulsants (anti-seizure medications), such as phenytoin (Dilantin), may be given to prevent seizures in people with brain tumours. These drugs can increase the risk of osteoporosis.
• other medical conditions, such as hyperparathyroidism (overactive parathyroid gland), rheumatoid arthritis (disease of the joints) and hyperthyroidism (overactive thyroid gland)
• low calcium and vitamin D intake
• too little exercise
• smoking
• too much alcohol
  • Having more than 2 drinks of alcohol a day on a regular basis can increase the risk of osteoporosis.
• too much caffeine
  • Having more than 4 cups of coffee a day on a regular basis may increase the risk of osteoporosis.

The more risk factors a person has, the higher the chances they will develop osteoporosis at some point in their life.

Symptoms

Osteoporosis can exist for years without symptoms, and a person may not realize they have osteoporosis until they break a bone. That is why it is called a silent disease. Some people with osteoporosis may also have:

• a loss of height over time
• a stooped posture
• rounding of the upper back (called kyphosis)
• bone tenderness or pain

Usually bone loss related to osteoporosis happens slowly and occurs after age 65. But people who have received cancer treatments that put them at high risk for bone loss may develop osteoporosis sooner. It can be difficult to determine exactly when osteoporosis might occur in someone with cancer or when they may notice symptoms.

Diagnosis

A bone mineral density test is done to measure the density of bones and check for osteoporosis. The most common bone density test is the dual-energy x-ray absorptiometry (DXA or DEXA).

• A person lies on a table and low dose x-rays are taken of the bone, usually at the lower spine and hip.
• The results tell the doctor how dense the bones are. The results may be reported as a T-score. A T-score compares the person's bone density to that of a young adult. The lower the result (often shown with a minus sign), the lower the bone density and higher the risk of fracture.

Categories of osteoporosis and T-scores

*World Health Organization (WHO) classification of osteoporosis based on bone mineral density.

The doctor may order a bone mineral density test before starting some cancer treatments in order to:

• provide a baseline to compare follow-up tests against
• watch for changes in bone density
• see how well a person is responding to osteoporosis treatment

Blood and urine tests may also be done to see how much osteoporosis is affecting the bones.

Prevention and management

There is no cure for osteoporosis, but there are ways to prevent and control bone loss.

Early detection

Detecting bone loss early is important in preventing fractures due to osteoporosis. It is recommended that women and men over 50 be assessed for risk factors for osteoporosis. Also, people should talk to their doctor about being tested for osteoporosis, especially if they have risk factors.

Calcium and vitamin D

Calcium is important for building bones, keeping them healthy and maintaining bone density. The main sources of calcium are milk and milk products such as cheese and yogurt. Broccoli, oranges, canned fish with bones and some grain products also contain small amounts of calcium.

Vitamin D helps the body use calcium, so it plays a role in keeping bones healthy. Vitamin D is naturally made by the skin when it is exposed to the sun. However, it is important to protect yourself from the damaging effects of sun exposure. Some foods naturally contain vitamin D, including oily fish such as salmon, tuna, sardines and herring. Milk and some margarines have vitamin D added to them. Vitamin D can also be obtained through supplements.

People at risk for osteoporosis should consider:

• Including more foods that contain calcium and vitamin D in their diet, especially oily fish and milk products.
• Talking to their doctor or pharmacist about taking calcium and vitamin D supplements, because dietary sources of these nutrients may not be enough to meet the amount needed to maintain health and prevent osteoporosis.
  • The doctor or pharmacist can suggest which supplement to take and how to take it.
    • Take supplements with food and do not take more than 500 mg of elemental calcium at one time.
    • The body can only absorb 500 mg of calcium at once, so divided doses may be needed.
    • Elemental calcium is the amount of calcium in a calcium supplement. For example, 1250 mg of calcium carbonate provides 500 mg of elemental calcium.
• Checking with a healthcare professional the recommended amount of calcium and vitamin D.
  • The recommended average daily intake (adequate intake or AI) differs according to age, sex and special circumstances like pregnancy and breast-feeding.
  • All sources of calcium and vitamin D must be included when adding up daily amounts, including diet and supplements.
  • The recommended daily intake for calcium and vitamin D is higher for osteoporosis prevention and treatment, based on age and risk.
  • Many experts are also considering that higher amounts of vitamin D may be necessary for optimal health.

Recommended daily intake of calcium and vitamin D for adults

Source: Dietary Reference Intakes. Health Canada. 2006.

Note: Based on the current growing body of scientific evidence that vitamin D may reduce the risk of some types of cancer, the Canadian Cancer Society has increased it recommendations for vitamin D intake. Canadian adults should consider taking a vitamin D supplement of 1000 international units (IU) a day during fall and winter months. Adults at higher risk of having lower vitamin D levels (such as the elderly, people with dark skin, people who don't go outside very much, or wear clothing that covers most of their skin) should consider taking a vitamin D supplement of 1000 IU a day all year round.

Physical activity

Regular physical activity can help prevent osteoporosis and reduce the risk of falls and fractures. Regular exercise can:

• help maintain bone density and may even improve it
• help people maintain a healthy body weight
• improve muscle strength, balance and coordination

Physical activity for a minimum of 30 minutes at least 3 to 4 times a week can help prevent osteoporosis. It is important to choose a variety of activities and intensities. Different types of physical activity include:

• weight-bearing exercises, such as walking, climbing stairs, low-impact aerobics, dancing and playing tennis
• strengthening exercises, such as using free weights, weight machines, rowing machines and stretch bands
• stretching or balancing exercises, such as yoga and Tai Chi

People who have been diagnosed with osteoporosis or who have had a fracture should talk to their doctor about a specialized exercise program.

Smoking and alcohol

Stop smoking and limit alcohol intake to maintain bone health and decrease the risk of osteoporosis.

Drug therapy

There are a variety of medications that may be used to help decrease bone loss and reduce fractures. The doctor will consider a person's medical history and current medications when discussing drug treatment options for osteoporosis.

Bisphosphonates

Bisphosphonates are drugs that bind to the surface of the bones and slow down the bone-eroding cells called osteoclasts. They strengthen the bone and may be used to prevent and treat osteoporosis. The main bisphosphonates used for osteoporosis are:

• alendronate (Fosamax)
• risedronate (Actonel)
• etidronate (Didrocal, Didronel)

Other types of bisphosphonates may also be used to treat cancer that has spread to the bone (bone metastases) or a type of cancer called multiple myeloma. They are used to reduce the number of bone fractures and reduce pain caused by bone metastases. These bisphosphonates include:

• clodronate (Bonefos, Ostac)
• pamidronate (Aredia)
• zoledronic acid (Zometa, Zoledronate)

Raloxifene

Raloxifene (Evista) is a type of selective estrogen receptor modulator (SERM). SERMs act like the hormone estrogen in some parts of the body, such as the bones, and act against estrogen in other parts of the body. Raloxifene helps increase bone density and is used to prevent and treat osteoporosis in post-menopausal women.

Hormone replacement therapy

Hormone replacement therapy (HRT) may be used to relieve the symptoms of menopause. Because estrogen plays such an important role in protecting a woman's bones, HRT may also be considered to prevent and treat osteoporosis. However, women who have had cancer should discuss the risks and benefits of HRT with their doctor. Other options for osteoporosis treatment are often explored first.

Teriparatide

A drug similar to parathyroid hormone, called teriparatide (Forteo), is a new drug used to treat osteoporosis. It helps new bone to be made. Teriparatide is used for severe osteoporosis or for people who cannot tolerate other osteoporosis treatments. It is also used when other treatments have failed.

Calcitonin

Calcitonin is a hormone made by the thyroid gland that controls the activity of the osteoclasts. Calcitonin slows down the osteoclasts, so it helps maintain bone density and increases it to a small extent. Calcitonin does not prevent osteoporosis, but it may be used to treat it and also helps relieve pain associated with fractures of the backbone (vertebrae).

Support

Osteoporosis Canada provides information about osteoporosis and support for people living with this condition.