Platelet hyperaggregability and increased α-adrenoceptor density in anorexia nervosa

Plasma norepinephrine concentrations in a group of malnourished patients with anorexia nervosa were significantly (P < 0.002) lower than those in an age- and sex-matched group of normal subjects. Platelet total α-adrenoceptor densities of these patients significantly (P < 0.002) exceeded those of the controls. The increased total α-adrenoceptor density was due to an increase in the α₂-adrenoceptor receptor subtype, which mediates epinephrine-induced platelet aggregation. Accordingly, the aggregation response of the patients’ platelets was significantly (P < 0.002) enhanced after epinephrine challenge. We suggest that the starvation-induced fall in plasma norepinephrine levels is associated with the up-regulation of platelet α-adrenoceptors. This, in turn, accounts for exaggerated epinephrine-induced platelet aggregation in anorexic patients.