Behaviors associated with eating disorders like anorexia and bulimia may be linked to a problem in how the body responds to hormones involved in appetite control and social behavior.

A new study shows an association between women with bulimia and anorexia symptoms and antibodies released by the immune system to attack brain hormones involved in appetite control and social interactions.

Researchers say the finding may lead to a better understanding of the biological underpinnings of eating disorders but stress that eating disorders are caused by a complex combination of environmental, social, and other factors as well as biology.

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In the study, which appears in the Proceedings of the National Academy of Sciences, researchers compared levels of the antibodies in 54 young women with anorexia and bulimia to those found in 41 similar, healthy women.

Previous Swedish research showed that most women with eating disorders displayed antibodies that reacted to a hormone involved in appetite control, called alpha-melanocyte-stimulating hormone (a-MSH).

In this study, researchers found elevated levels of antibodies against two more hormones found in the brain known as vasopressin and oxytocin in women with and without eating disorders. These hormones are primarily involved in water balance as well as social interactions.

Women with anorexia had significantly higher levels of antibodies against these three hormones than women with bulimia or healthy women.

In addition, researchers found levels of antibodies acting against a-MSH correlated with the severity of psychological symptoms associated with eating disorders in both women with anorexia and bulimia.

However, researchers also found higher levels of these antibodies in some healthy people without eating disorders, which suggests that high blood levels of these antibodies is not enough to cause eating disorders.

Because healthy women were also found to have antibodies against these hormones they add that this may constitute a mechanism of control.

They say the results suggest that behaviors associated with eating disorders may be related by hormonal dysfunctions regulated by the immune system.

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By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCE: Fetissov, S. Proceedings of the National Academy of Sciences, Sept. 26-30, 2005, online early edition.