Low urinary 6-sulphatoxymelatonin levels in patients with coronary artery disease

A decrease in nocturnal serum melatonin levels was reported in patients with clinically uncharacterized coronary artery disease. To assess whether there was a correlation between melatonin production and disease stage, we measured the nocturnal urinary excretion of 6‐sulphatoxymelatonin (an index of blood melatonin concentration) in patients with chronic stable or unstable coronary disease and in a group of age‐matched controls. Three groups of individuals were studied: a) 24 healthy subjects (mean age: 63±13 yr); b) 32 patients with chronic, stable, coronary disease (62±11 yr); and c) 27 patients with unstable angina (62±12 yr). For 6‐sulphatoxymelatonin measurement, urine was collected from 18:00 to 06:00 hr, within 48 hr of hospitalization in the case of unstable angina. 6‐Sulphatoxymelatonin was measured by a specific radioimmunoassay. Urinary 6‐sulphatoxymelatonin excretion was significantly lower in unstable angina patients than in healthy subjects or in patients with stable angina. 6‐Sulphatoxymelatonin correlated negatively with age in healthy subjects, but not in coronary patients. 6‐Sulphatoxymelatonin excretion in patients treated with β‐adrenoceptor blockers did not differ significantly from coronary patients not receiving β‐blockers. The results indicate that patients with coronary disease have a low melatonin production rate, with greater decreases in those with higher risk of cardiac infarction and/or death.