Anorexia and Bulimia Nervosa may be caused by an auto-immune disorder where antibodies attack the hypothalamus or pituitary.

Three-quarters of the anorexic and bulimic women studied by Serguei Fetissov of the Karolinska Institute in Stockholm carry blood antibodies targeted against appetite centres in the brain, he finds. Just 16% of those without eating disorders have such antibodies1.

Another article with additional details.

To test the theory, the investigators withdrew blood serum from 57 women between the ages of 17 and 42 who had anorexia, bulimia or both. Most of the women (74 percent) produced antibodies that, when applied to sections of rat brains and rat pituitary glands, selectively attached to cells that produce three specific neuropeptides: alpha-MSH, ACTH and LHRH.

This is a fascinating result. The targeting of adrenocorticotropic hormone suggests that stress may trigger the auto-immune response. But there may be a genetic predisposition for this inappropriate immune response. It brings up the question of just what other behavioral and endocrine disorders of currently unknown cause might be caused by auto-immune responses.