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Bone Loss: A Serious Complication of Anorexia

By Karen K. Miller, MD
Reprinted from Eating Disorders Recovery Today
Fall 2006 Volume 4, Number 4
©2006 Gürze Books

Bone loss is a serious complication of anorexia nervosa that effects more than 85 percent of anorexic women and for which there is no established, adequate therapy.

What is bone density and how is it measured?

Bone density refers to the thickness of a bone. When bone density decreases significantly, the risk for fracture increases. There are several conditions and medications that are harmful to the bones before menopause, including steroid use and anorexia nervosa.

Bone density can be measured in several ways. The most common is with a DXA machine,1 which uses a very low amount of x-rays to measure the spine, hip and/or wrist. The procedure is painless and yields a Z score. This compares the patient’s bone density to that of an average healthy woman of the same age, and a T score, which compares her to that of an average woman at the peak of her skeletal health.

How prevalent and severe is bone loss?

Bone loss is very common in anorexia. A recent study reported that fewer than 15 percent of women with the disorder have normal bone density at the spine, hip, and wrist. Moreover, the bone loss is typically severe; it is not uncommon for a woman in her 20s to have the bone density of a typical 80- or 90-year-old woman. This results in an increase in fracture risk to seven times the usual rate for young women.

Why do women with anorexia nervosa lose bone?

All of the factors contributing to bone loss are not known, but among those that are known include depression, especially in conjunction with borderline personality disorder, smoking, and carbonated sodas, including diet sodas. It also appears that lack of adequate nutrition is fundamental, and leads to the breakdown of bone primarily by depleting normal hormone levels, including estrogens, testosterone and IGF-1, a hormone that is related to growth hormone.

What can you do to repair your bones?

The best therapy for bone loss is nutritional recovery. Therefore, concentrating on recovery with the help of a multi-disciplinary team is the best treatment. Interestingly, in the absence of nutritional recovery, estrogen therapy—in the form of birth control pills or lower dose therapies typically used for postmenopausal hormone replacement therapy—is NOT effective to reverse bone loss and is not recommended unless needed to prevent pregnancy. The artificial menstrual periods can mask the serious effects of the eating disorder on the reproductive system. It is not known whether low doses of estrogen would be effective in adolescents with anorexia in order to mimic puberty, and this is currently under study.

Calcium 1200 to 1500 mg daily and vitamin D, 400 to 800 IU daily, which aids in the absorption of calcium from the GI tract, are important but do not alone (i.e., in the absence of complete nutritional recovery), repair the skeleton. Although weight-bearing exercise is helpful to build bone in postmenopausal women, it can have the opposite effect if the energy spent in exercising is not replaced by adequate calories. Moreover, exercise can be harmful in other ways. High impact exercise and falls can result in fractures.

Is there research being done?

Research is desperately needed to investigate the reasons that women with anorexia lose bone at such a rapid rate and to identify therapies to reverse the bone loss. At Massachusetts General Hospital in Boston, researchers are currently studying different therapeutic options and welcome your participation in these studies. For more information, please send an e-mail to NEDResearchstudies@partners.org or call 617/724-7393.

Reference

  1. A T score less than –1.0, or more than one standard deviation below normal peak bone density, provides a diagnosis of "osteopenia" and a T score less than –2.5, or more than 2 ½ standard deviations below normal peak bone density, confers a diagnosis of "osteoporosis." Both of these diagnoses are common after menopause.

About the Author

Karen K. Miller, MD, is an endocrinologist at Massachusetts General Hospital and Harvard Medical School in Boston who conducts research studies into the causes of bone loss of anorexia nervosa and into potential therapies to reverse such bone loss.