Adrenaline-induced hyperaggregability of platelets and enhanced thromboxane release in anorexia nervosa

Platelet aggregation and thromboxane A2 release in response to adrenaline and the relationship of this response to body weight was investigated in female patients with anorexia nervosa. Platelets obtained from patients with body weights below 75% of the expected average weight (Group I) showed significantly greater aggregation and TXA2 release in response to adrenaline when compared with controls matched for sex and age. Patients with body weights 75-95% of the expected average weight (Group II) did not show enhancement of platelet aggregation or TXA2 release. In Group I patients, platelet hyperaggregability and enhanced TXA2 release induced by adrenaline tended to normalise following inpatient treatment and weight gain: with 0.5 mumol/l adrenaline, the pre-weight gain median aggregation was 65%, whereas the post-weight gain value was 37% - P less than 0.01. Markedly underweight patients also had hyperaggregability following stimulation with ADP and collagen. This hyperaggregability also tended to normalise after weight gain but these changes were not statistically significant. Platelet hyperaggregability (especially in response to adrenaline) in anorexia nervosa is therefore secondary to weight loss and reverts to normal with normalisation of weight. These changes may reflect the previously documented increase in platelet alpha-adrenoceptors in thin patients with anorexia nervosa and their normalisation following weight gain. However, the hyperaggregability in response to agonists other than adrenaline suggests that an additional post-receptor mechanism may be involved.