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What is osteoporosis? Think of it this way: Healthy bones are in a state of continuous breakdown and rebuilding. This process, called remodeling, is performed by specialized cells called osteoclasts, which resorb (break down) old bone, and osteoblasts, which form new bone.
In young adults, remodeling happens in a balanced fashion that maintains bone density over time. But as we age, and particularly when women reach menopause and estrogen levels plummet, the process is no longer balanced—more bone is broken down, and bone building is unable to keep up. The result is reduced bone density, an increased risk of bone mineral density (BMD) test scores of osteoporosis -2.5 or osteoporosis -3 bone density T score—and brittle bones that are more prone to fracture.
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How Your Bone Density Is Measured
The standard approach for measuring bone density is dual energy X-ray absorptiometry (DEXA, also written as DXA), which measures the density of bones in the spine, hip, and wrist, since these are the areas most likely to be affected by osteoporosis and by the osteoporotic fractures that can result from a bone density score in the range of osteoporosis -2.5 and or osteoporosis -3.
A DXA scan takes about 20 minutes and is painless. It is essentially an X-ray procedure that measures how many grams of calcium and other bone minerals are packed into a segment of bone (typically the spine, hip, or forearm, since these are the bones most likely to fracture due to osteoporosis). Bone mineral density is calculated on the basis of how much of the X-ray beam passes through the bone.
Other methods of measuring bone density include ultrasound (also called a sonogram), and computed tomography (CT) scans. An ultrasound utilizes high-frequency sound waves that travel through soft tissue but “bounce” off dense surfaces such as bones. As the sound waves bounce, they give off an echo that is shown as a darker shade of gray on the resulting images. In a CT scan, a series of X-rays are taken from different angles, and then combined to produce a cross-sectional image of soft tissue or bones. However, the results from ultrasound may not be as precise as the results from a DXA, while CT scans expose the body to more radiation than DXA.
A smaller type of bone scanner can be used to measure peripheral bone mineral density in the finger, wrist, or heel. These types of machines, often available in pharmacies, don’t provide an accurate a measure of bone density; still, if a peripheral test is positive, discuss with your doctor whether you should have a follow-up scan of your hip or spine.
How Your Bone Density Is Calculated
DXA results compare your bone density to that of a healthy 30-year-old adult and come back as what’s called a “T-score.” An osteoporosis T score in the range of -1 and above indicates normal bone density, and between -1 and -2.5 indicates low bone density, which is sometimes referred to as osteopenia. Osteoporosis -2.5 indicates that you do have you may be on the threshold of full osteoporosis, and if your T score is osteoporosis -3, you have osteoporosis -3 there’s usually no question you are suffering from the condition.
These bone density T scores roughly reflect how much bone you’ve lost—for example, osteoporosis -2.5 equates to 25 percent bone density loss, and osteoporosis -3 equates to 30 percent bone density loss.
Protecting Yourself Against Fractures
It’s especially important to protect yourself from fractures as you get older—a 2016 study carried out by researchers at the University of California-San Francisco (UCSF) suggested that one in every two older adults who suffers a hip fracture will never fully regain their health, mobility, and independence.
“The likelihood of recovery to pre-fracture level of function was less than 50 percent regardless of one’s previous level of function,” says study author Victoria L. Tang, MD, assistant professor of medicine in UCSF’s Division of Geriatrics. “The likelihood of returning to a high level of function was particularly low in those who were older than age 85, had multiple comorbid conditions, or had dementia.”
Do you need a bone density test to help monitor your bone health and warn you if you are at risk for fractures? Your doctor can help you decide if and when you might need one. In general, this testing is recommended for women age 65 and older along with younger postmenopausal women who have further risk factors for osteoporosis. Additional risk factors include lower body weight (less than 154 pounds, which means you might start out with less bone mass), a family history of osteoporosis, and a previous fracture after age 50. Smoking and three or more alcoholic beverages daily also raise your risk.
Your doctor also may advise that you be screened for osteoporosis -2.5 or osteoporosis -3 if you have certain co-morbidities, such as an overactive thyroid, or a gastrointestinal condition that impedes the absorption of calcium (for example, Crohn’s disease).
Some medications, including corticosteroids such as prednisone (Deltasone, Liquid Pred), some antidepressants, and proton pump inhibitors (PPIs), which are used to treat heartburn, also may weaken your bones.
The National Osteoporosis Foundation (NOF) also recommends bone density testing every one to two years for women taking osteoporosis medications. If you’ve recently started taking these meds, your doctor will likely refer you for a repeat DXA after one year to monitor your bone density scan results.
Bone Density Screening for Men
Just because osteoporosis is more common in older women doesn’t mean that men shouldn’t take care of their bone health and also have their bone density checked. The American College of Physicians recommends that men get regularly assessed for osteoporosis risk factors, starting at age 50. The Endocrine Society advises men to get a routine T score for osteoporosis when they reach 70 years of age.
Mary Ruppe, MD, an endocrinologist at Houston Methodist, says that osteoporosis treatment options for men are similar to those available for women who have an osteoporosis -2.5 or osteoporosis -3 bone density test score.
There are several approved medications that alter the cycle of bone formation and loss to help preserve bone strength—Dr. Ruppe emphasizes that the key is diagnosing the condition so that a treatment regimen can begin. “Each year, approximately 80,000 men will suffer a hip fracture, and studies have shown they have a higher mortality rate after a hip fracture than women of the same age,” Dr. Ruppe notes.
“Such data underscores the importance of routine osteoporosis screening for men.” Dr. Ruppe adds that if a man is diagnosed with osteoporosis, his physician can begin treatment and order additional screenings to identify causes of low bone density that can cause other medical issues, such as vitamin D deficiency or low testosterone levels.
Originally published May 2016 and updated.