What is Osteoporosis?
Bone is living tissue in the body that continually breaks down and is then restored. During the restoration process, the bone may lack some of the essential minerals that are critical to strengthening bones and increasing the density of the tissue. This lack of minerals can happen due to changes in diet or hormonal changes in the body. Osteopenia occurs when the bone density becomes diminished. When the loss of density becomes significant to the point that the bone is distinctly weakened and the risk of fractures increases, it is called osteoporosis (meaning porous bone).
What Are the Risks of Osteoporosis and Who Is at Risk?
Porous bones significantly increase the danger of fractures. These fractures most commonly occur in the hips, wrists, and spine, although other bones are also at risk. This degenerative condition can affect anyone of any age or race. However, women are at a much higher risk than men. Asian and Caucasian women are at higher risk than other ethnic groups. A telling statistic from the National Osteoporosis Foundation is that, in addition to the approximately ten million Americans who have osteoporosis, around 43 million Americans have decreased bone mass and are, therefore, more likely to develop the disease.
Most people who are at risk of developing the disease are unaware of it. It is often referred to as the “silent disease” as there are few noticeable symptoms until a bone fracture occurs. This type of fracture most commonly occurs in the hip bones, the spinal vertebrae, or the wrists. Very little pressure or stress can cause the bone to break, resulting in significant pain and extended rehabilitation. In some cases, permanent disability may result. In some instances, the fracture may cause severe debility, affect the general or overall health of the person with osteoporosis, and be a contributing factor in their death.
How Does Osteoporosis Develop?
Bones are generally comprised of calcium phosphate and type-1 collagen protein. The collagen protein forms the spongy network of tissue that is then mineralized by the calcium phosphate, adding strength and flexibility to the bone. This network of living tissue is continuously replaced over time. Osteoclasts dissolve the bone tissue on a microscopic level and enzymes then break down the collagen protein network. This process is referred to as bone resorption. Resorption is followed by the creation of new bone by osteoblast cells. The entire process of dissolving and rebuilding bone is called bone remodeling or bone turnover. This process continues throughout life, taking around ten years for the whole skeleton to be replaced.
In children, bone formation proceeds faster than bone resorption, so bone mass increases. At around the age of 20 years, the bone resorption rate and bone mass reach their peaks. Following this, bone resorption starts to overtake the process of bone formation, resulting in a decrease in bone mass with age. Factors that can contribute to the decline in bone mass and the development of osteoporosis later in life include:
- Vitamin D and calcium deficiencies, especially during childhood
- Using medications that have a high dose of glucocorticosteroids. These are doses exceeding what would be prescribed for the treatment of asthma or nasal allergies through an inhaler.
- Eating disorders such as anorexia or bulimia which lead to mineral deficiencies
- Gastrointestinal surgery that can affect the absorption of minerals
- Inactivity or lack of exercise
- Smoking and consuming alcohol in excess
Diseases that can affect bone health include:
- Cushing Disease
- Thyroid disease such as hyperthyroidism
- Rheumatoid Arthritis
- Kidney Disease
A genetic link has also been established, and those with a familial history may be predisposed and therefore at a greater risk of developing osteoporosis.
A decrease in the production of the hormone estrogen during menopause and in post-menopausal women increases the rate of bone loss. Early menopause can contribute to the loss of bone mass to an even greater degree. The National Osteoporosis Foundation says that 20% of bone mass can be lost in the first 5-7 years after menopause. A decrease in testosterone levels in men can also increase the risk of loss of bone mass.
What Are the Two Types of Osteoporosis?
Primary Osteoporosis is age-related and develops without there being any apparent underlying cause. Although it has a higher rate of incidence in women, it can also affect men, especially older ones. As mentioned above, the increased rate of bone loss after menopause in some women results in bone fractures being more likely to occur at a relatively younger age. However, in most cases, fractures only first occur between the ages of 60 and 80. The most common of these fractures occur on vertebrae due to compression of the spine. The progression of the disease may be decelerated by changes in lifestyle, calcium, Vitamin D supplements, and other medications to reduce bone loss can slow the progression of this type of osteoporosis.
Secondary osteoporosis is defined as bone loss that occurs due to any other cause that is not age-related. It can affect both men and women equally and may be caused by a wide range of medical conditions such as Cushing disease, chronic kidney disease, rheumatoid arthritis, hyperparathyroidism, or multiple myeloma. Some medications, such as glucocorticoids, lithium, and anti-epileptic prescription drugs, may also contribute to bone loss.
Testing for Osteoporosis
There are several goals to testing for osteoporosis:
- Does the patient have osteoporosis?
- Does the patient have low bone mass and an increased risk for osteoporosis?
- Is the patient menopausal, or is a hormone deficiency present?
- Does the patient have any other health or underlying condition that could be contributing to bone loss?
A bone density scan is the most common test that is performed to establish bone mass and whether bone loss has occurred. These scans are customarily performed after an unexpected bone fracture or to monitor the efficacy of osteoporosis treatment.
Guidelines for screening for osteoporosis have been established by a variety of different organizations, including:
- American College of Obstetricians and Gynecologists
- National Osteoporosis Foundation
- U.S. Preventative Services Task Force
These agencies recommend that all women over the age of 65 be screened for osteoporosis. However, screening at a younger age is recommended for women that have certain risk factors that may increase the likelihood of bone loss.
In addition, the National Osteoporosis Foundation recommends screening for all adult males over the age of 70 years. Where certain risk factors exist, screening should take place between the ages of 50 and 69 years for men.
Non-Laboratory Testing for Osteoporosis
A Bone Mineral Density (BMD) test is the most common and primary evaluation performed by a medical practitioner to identify low bone mass and diagnose osteoporosis. The BMD test is preferably performed using a Dexa-Scan (dual-energy X-ray absorptiometry or DXA) to measure the density of bone in the hip and spine using low energy-x-rays. A baseline or mean for reporting is established according to the peak bone mass reached in young adults as follows:
- A BMD value of 1 standard deviation below the young adult mean is normal.
- A BMD value of between -1 and -2.5 standard deviation below the mean indicates osteopenia.
- A BMD value of -2.5 standard deviation or more below mean may be indicative of osteoporosis.
A calculator developed by the World Health Organization has also become available to medical practitioners to evaluate the future risk of hip, spine, or wrist fractures after the age of 40 years. This tool, called the FRAX, can be used on paper or online and measures the mineral density and takes into account a number of different risk factors in an algorithm that is designed to estimate the probability of a bone fracture over the next ten years. The National Osteoporosis Foundation has adapted the FRAX tool for the U.S.A. and released it in their Clinician’s Guide.
Portable devices for BMD screening are available at some pharmacies, health fairs, and so on. These portable scanners use fingers or the heel of the foot to measure bone density. They are, however, not as accurate as the DXA scan, but if a low bone density is detected, a DXA scan may be used for confirmation.
Additional imaging tests that are available to measure BMD to diagnose osteoporosis include:
- CT scans or Computerized Tomography
Body composition analysis is a general screening test that determines the body weight relative to the percentage of fat, muscle, water, and bone. There are a number of ways to measure general body composition using a range of specialized instruments. If this type of screening is performed regularly, the results can be analyzed year by year and assist in the early detection of bone loss.
Another diagnostic test is a bone scan that evaluates the condition of the bones but is not the same as a BMD. A bone scan is invasive and uses nuclear medicine to identify serious bone disorders, unlike BMD testing, which is non-invasive and used to diagnose osteoporosis. The bone scan procedure involves injecting a radioactive tracer into a vein located in the arm. The tracer is absorbed into the bones as it travels through the bloodstream. The level of radioactivity in the bones is then measured to identify conditions such as Paget’s disease, metastatic cancer, infection, and other causes of unexplained bone pain. Bone scans detect bone conditions earlier than x-rays and may be ordered if a patient presents with frequent bone fractures.
Laboratory Testing for Osteoporosis
A medical practitioner may order the following blood tests if osteoporosis is suspected:
- Calcium levels in the blood, which are usually normal in osteoporosis, but elevated levels could be indicative of other bone diseases.
- Vitamin D deficiency may lead to lower absorption of calcium.
- T4 and Thyroid Stimulating Hormone (or TSH) thyroid testing to detect thyroid disease or disorders.
- Parathyroid hormone (or PTH) test to identify or eliminate hyperparathyroidism.
- Follicle Stimulating Hormone (or FSH) testing to detect menopause.
- Testosterone deficiency test for men.
- Protein electrophoresis to detect abnormal proteins that are a byproduct of multiple myeloma (a type of cancer) which can attack and break down bone tissue.
- Alkaline phosphatase (or ALP) testing to check for elevated levels that could be indicative of bone problems.
Bone markers are blood and urine tests which may sometimes be performed to determine and monitor bone resorption and formation rates. They are not, however, used as diagnostic tests.
Bone resorption tests are performed to measure the rate of bone loss over a period of time. Markers are checked before and after treatments to evaluate whether there has been a decrease in bone loss. These types of tests, used to monitor the efficacy of treatment, include:
- C-telopeptide (or CTx))
- Urinary collagen type 1 cross-linked N-telopeptide (or NTX)
- Deoxypyridinoline (or DPD)
- Pyridinium Crosslinks
- Urinary hydroxyproline
- Tartrate-resistant acid phosphatase (TRAP) 5b
- Bone sialoprotein (BSP)
Tests measuring bone formation (Bone formation markers) may be used to evaluate the rate at which the body produces bone. These tests include:
- Bone-specific alkaline phosphatase (or ALP)
- Osteocalcin (bone gla protein)
- Procollagen Type 1 N-Terminal Propeptide (or P1NP) and C-terminal (or C1NP)
Prevention and Treatment of Osteoporosis
Prevention is the best treatment for osteoporosis. Even though preventative measures can’t eliminate every case of osteoporosis, they can certainly help reduce the risk. Some preventative measures include eating foods with plenty of calcium and vitamin D (and supplements as required), weight-bearing exercise (like walking and resistance training), moderating alcohol consumption, and quitting smoking.
According to the American College of Obstetricians and Gynecologists, a woman should have a vitamin D level of at least 20 nanograms per milliliter (ng/mL). The earlier these lifestyle changes are implemented, the more they can help. Maximizing bone mass, and minimizing bone loss during aging, should help to prevent or reduce osteoporosis.
There is a variety of treatments available for those who are at increased risk of osteoporosis, those who have decreased bone mass, and those who have been diagnosed with osteoporosis (and who may have already suffered a bone fracture). These treatments include bone-forming (anabolic) mediations and antiresorptive medications.
It is vital for people who have osteoporosis to work with their physician to determine which treatments are appropriate and which lifestyle changes may help them conserve bone mass and prevent falls. People who take medications that can lead to bone density loss, such as prednisone or other glucocorticoids and some anticonvulsant medications, should speak with their physician about alternative medications.