Serotonin metabolism in patients with decreased renal function

Serotonin metabolism was investigated in 15 patients (8 women, 7 men) with decreased renal function (clearance of endogenous creatinine = 0.07-0.74 ml/s) and compared to the values obtained in healthy controls. In spite of thrombocytopenia, the patients' platelet serotonin concentrations (1.99-47.6 nmol/10(9) platelets) as well as the plasma serotonin levels (190-2,176 nmol/l) were significantly higher than in controls (1.36-7.87 nmol/10(9) platelets, p less than 0.05; 0-500 nmol/l, p less than 0.001). The low urinary serotonin output (0-414 to 167-1,187 nmol/24 h in controls, p less than 0.001) probably reflects its decreased synthesis in the residual renal parenchyma. 5-Hydroxyindolacetic acid was excreted in normal amounts. The impairment in serotonin metabolism is closely correlated with the decrease in renal function. The data document accumulation of serotonin in the circulation. This impairment could contribute to platelet hyperaggregation and/or consumptive hypocoagulation, maintenance of hypertension, and acceleration of atherosclerosis.