Patient Information

Premenopausal Women
Low Bone Density in Premenopausal Women

How do I know if I am premenopausal?

You are premenopausal if you are having normal menstrual cycles with monthly periods- unless, of course,
you are pregnant. If you are having irregular periods, then a blood test may show your menopausal status.

When am I no longer premenopausal?

You officially become postmenopausal one year after your last period. The usually occurs at about age 51.
If you stop having periods before age 45, it is called “premature menopause.” This may occur naturally or
due to disease of the ovaries. There is normally a transition zone called“perimenopause” that begins a few
years before your last period and ends one year after your last period. During perimenopause there may be
fluctuations in hormone levels that cause irregular periods and hot flushes.

What if I have a hysterectomy or removal of my ovaries?

If you are premenopausal woman who has both ovaries removed, you instantly become postmenopausal. If your
uterus is removed but at least one ovary remains, you will stop having periods but remain premenopausal as long
as you continue to have normal hormone levels. In this case, you may not know when you become perimenopausal
or postmenopausal, unless you have symptoms such as hot flushes. If there is any doubt, a blood test may help
decide when you are no longer premenopausal.

What does all this have to with my bones?

A lot. The estrogen hormones produced by your ovaries during the premenopausal years help to keep your bone
density stable. Normally, your bone density will change very little until you become perimenopausal or postmenopausal,
at which time you are at risk for rapid bone loss. While it is unusual for premenopausal women to have osteoporosis,
about 30% of postmenopausal women will eventually develop it.

When should a premenopausal woman have a bone density test?

Routine bone density tests are not recommended in premenopausal women, because the chance of finding a bone problem
is very small. However, in some situations, a bone density test may be helpful. A bone density test should be done in a
premenopausal woman with any of the following:

• Bone fracture with little or no trauma.
• Medical problem (such as celiac disease or surgical removal of the stomach) or
  medication (such as prednisone or epilepsy drugs) known to cause osteoporosis.
  
• Medication for treatment of osteoporosis is being considered.
• Medication is being given for osteoporosis, to monitor the treatment effect.
  

How common is low bone density in premenopausal women?

The answer depends on how “normal” and “low” is defined. If we define normal in the same way that we do for most other
medical tests, then about 2.5% of premenopausal women have low bone density. This corresponds to a “Z-score” at the hip
or spine that is below -2.0. The Zscore compares your bone density to that of average women your age, with a Z-score
of -2.0 meaning your bone density is about 20% less than average.

Do I have osteoporosis?

A diagnosis of “osteoporosis” is made in a postmenopausal woman when a bone density test shows a T-score (a comparison
of the patient’s bone density with that of a healthy young woman) -2.5 or less, or if a low-trauma fracture has occurred. In a
premenopausal woman, osteoporosis cannot be diagnosed by bone density testing alone, since the relationship between bone
density and the risk of fracture is not the same as it is in the postmenopausal years. Bone density is considered to be low in a
premenopausal woman if the “Z-score” is below -2.0. In order say that a premenopausal woman has osteoporosis, it is necessary to have a Z-score below -2.0 AND have a disease or condition associated with osteoporosis or increased risk of bone fracture. For example, if your Z-score is below -2.0 and you are taking prednisone, then a diagnosis of osteoporosis can then be made.

If my bone density is low, what does it mean?

Most premenopausal women with low bone density are simply lower than average, just as weight or height may be lower than
average. Low bone density does not mean that a bone disease is present. Having a bone density less than average does not
necessarily mean that you have lost bone, since we probably don’t know if you ever had an average bone density in the first place. In most cases, the best bone density ever achieved, called “peak bone mass,” was lower than average. This is primarily due to inherited genetic factors, but lifestyle factors, such as calcium and vitamin D intake in childhood, also play a role. In most premenopausal women with low bone density, the bones are healthy and strong, with a low risk of breaking.

Do any tests need to be done?

If bone density is extremely low, or if low-trauma fractures have occurred, then laboratory tests or X-rays may be done to evaluate for contributing factors. The most common blood tests measure the blood count, calcium and phosphorous, liver and kidney function, and thyroid level. Often a 24-hour urine collection is done to measure calcium. Other tests may be done depending of the circumstances. Previously unrecognized problems such as hyperthyroidism, hyperparathyroidism, celiac disease, hypercalciuria, and Cushing’s syndrome may be found.

How can it be treated?

Premenopausal women with low bone density should take care to get an adequate daily intake of calcium and vitamin D, and exercise regularly. Since fracture risk is usually low, there is generally no reason to restrict physical activities. If there is concern that there is ongoing bone loss, then a repeat bone density test may be done a few years after the first one. If a disease or contributing factor is found on diagnostic testing, then that should be treated. In rare cases, osteoporosis medication will be prescribed. The effects of osteoporosis medications on subsequent pregnancies are unknown. When the time of perimenopause begins, usually in the late 40s to early 50s, there is a risk of rapid bone loss that may require additional care.

E. Michael Lewiecki, MD                                    
Lance A. Rudolph, MD

This page update 01/10/08