How often to have a bone density test?


Question from Lisa: I have been on tamoxifen for 3 years. I was told to take 1500 mg of calcium a day by my oncologist. My primary physician has indicated that this is too much and says that 500 to 1000 mg per day is enough since I eat foods, which contain calcium. What is the best thing? Also, how often should I have a bone density test to assure that I am not at risk?
Answers - Charles Shapiro Tamoxifen by itself has a protective effect on bone density and bone mass. It acts like estrogen in terms of its protective effects on bone loss. Tamoxifen is an anti-estrogen in terms of breast cancer, but it has estrogen action in the bone and that's why it tends to preserve bone mass in postmenopausal women. However, it is not as good as other treatments like bisphosphonates. As for the question about what's the right dose of calcium, I think that's individualized. You should get 1,000 - 1,500 mg; the point is there's no right answer here. You should be aware of the need for supplemental calcium.
Marisa Weiss, M.D. It's also important to know that your body cannot absorb all of that calcium in a short period of time. It can only absorb a little bit at any one time and therefore it is important to take your 1500 mg of calcium in divided doses or in various meals through the day. If you're taking it by pill, usually your body cannot absorb more than 500 mg from any one dose. Most people take it in 2-3 doses per day.
Charles Shapiro As for bone density testing, the standard test for detecting bone loss is a DEXA scan which is an easy test. It takes 15 minutes or so and it gives comparable or less radiation than a chest X-ray. A DEXA scan works by measuring bone mass and comparing that to an age-matched normal population of women, so you know where you stand relative to the norm. For a DEXA scan you usually lie on a sort of table, depending on the machine. It usually takes less than 20 minutes. The monitor moves up and down the body but there's no donut.
Marisa Weiss, M.D. Some doctors have a machine in their office that measures the density of bone. They may ask you to put your hands or your foot or ankle into this machine in order to measure the density. This is not the best way to get a good comprehensive look at the health of your bones. It is important to know that there are different kinds of bone in your body. Your backbone is one type of bone, and your long bones that are in your arms and legs are a different kind of bone. Plus, your hands and your feet take a lot of abuse and the bone strength in those areas may be affected by trauma or varied usage.

The DEXA scan is considered to be the most effective way to measure your bone strength. It measures the thickness of bone throughout the body and it also compares your bone strength to the bone strength of other women who are in your age group. In addition, it creates a standardized report, which goes into your chart and becomes a document that future scans can be compared to. This is useful over time, as your doctor charts your progress from year to year.
Charles Shapiro The recommendation for how often to be tested is once a year.
Marisa Weiss, M.D. But as we said, all of these decisions are very much individualized from one person to another. It may be that you have special circumstances that may make your doctor depart from the standard recommendations.

On Wednesday, August 21, 2002, our Ask-the-Expert Online Conference was called Keeping Your Bones StrongCharles L. Shapiro, M.D. and Marisa Weiss, M.D. answered your questions about how to measure the strength of your bones, how to find out your risk for osteoporosis, and what you can do to lower that risk.

The materials presented in these conferences do not necessarily reflect the views of Breastcancer.org. A qualified healthcare professional should be consulted before using any therapeutic product or regimen discussed. All readers should verify all information and data before employing any therapies described here.

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Copyright 2010. All rights reserved.

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