Impaired nocturnal secretion of melatonin in coronary heart disease.

Patients with coronary heart disease have increased nocturnal urinary noradrenaline. Because melatonin suppresses sympathetic activity, we measured serum melatonin concentrations at night (0200 h) in 15 patients with coronary heart disease. Melatonin was significantly lower in the patients than in 10 healthy controls (median 7.8 [interquartile range 6.5-11.8] vs 36.2 [32.2-42.5] pg/mL, p < 0.0001). Thus, impaired nocturnal secretion of melatonin is associated with coronary heart disease.