It’s a question I hear all the time now, from my patients, my
friends, and my relatives: “Should I get a bone density test?” You may
have heard about bone density testing, or DEXA scanning, or your doctor
may have prescribed the test for you as you entered your menopausal
years. This article will help you to understand what the test is, who
should have it, and how it is interpreted. —Beverly
Vaughn, MD, Medical Coordinator, Menopause and You Program
Why does bone density matter?
In childhood and adolescence, a normal female’s bones increase in both
length and density, growing both bigger and stronger. Once full height
is reached, usually in the mid-teens for girls, bones continue to become
denser until around the age of 30, when peak bone density is reached.
Successful growth of bones requires sufficient calcium and vitamin D
intake, sufficient weightbearing activities, and the interaction of
several hormones, including thyroid hormone, parathyroid hormone, and,
notably, estrogen. If all has gone well, peak bone density means bones
are strong and hard. They can stand up to a great deal. It takes quite a
fall or other injury to fracture such a bone.
After peak density is reached, bones decline in density about one half
of one percent yearly for the following five years. After that, the rate
of loss levels out to a slower, steady rate. The actual amount of bone
lost during the first few years of menopause depends, again, on calcium
and vitamin D intake, and on the levels of the previously mentioned
hormones. Sometimes medications taken can also change the rate of loss.
For instance, hormone replacement therapy decreases the rate of bone
loss, while long-term use of steroid medications, certain diuretics and
certain progesterones increases the rate. Other factors, such as
exercise, smoking, and alcohol intake, also play a role, as do genetics:
A woman whose mother or sisters have bone loss is more likely to also
have bone loss. Finally, a woman whose peak bone density was low to
begin with because of illness, malnutrition, or medication will end up
in menopause with a lower bone density than her cohorts.
Does loss of bone density mean osteoporosis and fractures?
Clearly, not every woman in menopause develops osteoporosis. Some women
retain a normal, healthy bone density well into older adulthood, and
some women have mild declines in bone density that we refer to as
osteopenia. It is important to find out if you have osteoporosis, or
osteopenia that is headed toward osteoporosis, because the condition
puts women at risk for painful spontaneous collapse of the vertebrae,
spine deformity, or fracture of the hip and other bones with minimal
impact, which may in turn lead to disability and other complications.
The only reliable way to determine your bone density is to have a DEXA
What exactly is a DEXA scan?
DEXA stands for dual energy X-ray absorptiometry. The test measures the
amount of X-ray beams absorbed by the subject’s bones, telling the
reader how dense the bone material is. The test takes only moments, is
completely noninvasive, and exposes the patient to much less radiation
than a chest X-ray.
A computerized report is generated, which compares the density of the
subject’s bones to that of the average for her age (a result known as
the Z-score) as well as to that of a normal woman at peak bone density
(the T-score). The T-score is the important score, because it is the
decrease from peak bone density that determines if one
has osteoporosis or osteopenia. A T-score greater than –1 (one
standard deviation below peak) is considered normal. A T-score from –1
to –2.5 is considered to indicate osteopenia, and a T-score below –2.5
(more than 2.5 standard deviations below peak bone density) is
So should I have a DEXA scan?
If you are at or close to menopause (you’ve stopped having periods
altogether or you are having them very infrequently and your doctor
believes it is due to menopause) and you have never had a DEXA scan, you
should have one. Premenopausal women with certain medical problems, such
as prolonged steroid use, unexplained loss of height, unexplained
fractures, anorexia nervosa, or certain endocrine abnormalities, may
also need a DEXA scan. If you have had a previous scan, your doctor may
ask you to have repeat scans at intervals of 18 months or so to compare
to the previous scan, as a way to follow ongoing bone loss or monitor
treatment for bone loss.
What happens if my DEXA scan indicates a problem?
If your DEXA scan comes back abnormal, your doctor may want to do some
blood tests to be sure there is not a correctable underlying cause for
bone loss, other than lack of estrogen in menopause.
If the result shows osteopenia, your doctor will encourage optimal
exercise and calcium and vitamin D intake. He or she may also consider
other treatment, depending on your age, the actual T-score, and other
risk factors, but in many cases, lifestyle measures and a follow-up DEXA
are all that is necessary.
If you have osteoporosis, your doctor will again stress exercise and
calcium and vitamin D, but will probably also offer one of several other
options. The options, depending on your other health issues, may include
the popular drug Fosamax, or its close relatives, Actonel or Boniva.
These drugs have been shown to increase bone density in postmenopausal
women. Other medications commonly used to treat osteoporosis are Evista
(hormone replacement in pill form), Menostar (a low-dose estrogen
patch specifically for osteoporosis/osteopenia), Miacalcin nasal spray,
and several injectable medications. Your doctor will follow your
progress with repeated DEXA scans.
This article is part of the Menopause and You library,
a Web-based program sponsored by Women’s Health Source.
It is intended as an information resource providing guidelines for
women. As always, check with your own healthcare practitioner with your
specific concerns and questions.
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