Bulimia's binges linked to hormone.

Bulimia's binges linked to hormone

Women with bulimia nervosa, an eating disorder characterized by recurrent binge eating, fail to secrete normal amounts of a hormone that induces a sense of satiety or fullness after a meal, new research indicates. The study suggests that a significant biochemical malfunction may lie behind the behavioral abnormality, and hints at the possibility of developing effective drug treatments.

Epidemiologists estimate that in the United States, up to 4 percent of young adult women and a far smaller fraction of men are bulimic. Although clinicians view the disorder as having both biological and psychological components, their failure to identify a biochemical mechanism, and the responsiveness of only some bulimics to antidepressant drugs, have left the disorder largely under the purview of psychotherapists.

"It's very exciting to think about the future of this field," says Thomas D. Geracioti Jr. of the National Institute of Mental Health in Bethesda, Md. He and Rodger A. Liddle of the Duke University Medical Center in Durham, N.C., report in the Sept. 15 NEW ENGLAND JOURNAL OF MEDICINE the impaired secretion of the hormone cholecystokinin (CCK) in a group of 14 bulimics. "Only 10 years ago were some of these substances being discovered in the brain, and already we're doing clinical research with them," Geracioti says. "Probably in our lifetime we'll be able to control appetite [abnormalities] pharmacologically."

Previous research has indicated that CCK plays a role in satiety. It is secreted in the small intestine in response to food intake, and has been found in the brain's hypothalamus with other hormones involved in a range of behaviors, including depression. Geracioti and Liddle, then at the University of California, San Francisco, found equivalent baseline levels of the hormone in bulimics and controls; but bulimics' peak CCK levels after eating a standardized, liquid meal were roughly half those of the controls. The bulimics also reported subjective feelings of being less full. Moreover, a subgroup of five bulimic patients given antidepressant drugs for eight weeks showed normal CCK responses after eating. The researchers offer no explanation for the drugs' effects on CCK secretion.

No single chemical is likely to control such a complex behavior as appetite, Geracioti and others warn, noting that further research may show that abnormalities in CCK secretion are as much a result as a cause of a vicious cycle of insatiability. And because hormone secretion can be influenced by psychological factors, they say, psychotherapy will remain useful as well.