1. Plasma and platelet free catecholamine concentrations were measured in 22 normal subjects and in 10 treated and 11 untreated patients with heterozygous familial hypercholesterolaemia.
2. Plasma noradrenaline concentrations were significantly higher in both treated and untreated hypercholesterolaemic patients than in normal subjects. Adrenaline concentrations did not differ.
3. Platelet noradrenaline levels were higher in untreated hypercholesterolaemic patients than in normal subjects.
4. Positive correlations between the plasma noradrenaline concentration and the platelet noradrenaline concentration were observed in both normal subjects and hypercholesterolaemic patients.
5. Combining the data for normal subjects and hypercholesterolaemic patients revealed that the plasma noradrenaline concentration correlated positively with the plasma cholesterol concentration. The platelet noradrenaline concentration was also found to correlate with the plasma cholesterol concentration.
6. Our results suggest that an increased plasma cholesterol concentration may be associated with increased sympathetic nervous system activity as indicated by elevated plasma and platelet noradrenaline levels. Increases in circulating catecholamines may contribute to the platelet hyperaggregability seen in familial hypercholesterolaemia.