Human melatonin and cortisol circadian rhythms in patients with coronary heart disease

Cortisol and melatonin have well known circadian rhythms, coupled to the solar day. Melatonin has been shown to serve as an endogenuous "Zeitgeber" (time giver) and is secreted by the human pineal gland throughout the night but not during the day. Patients with coronary heart disease (CHD) have significant depressed nocturnal melatonin secretion compared to healthy individuals (Brugger et al., 1995). In addition to our previous study we measured serum concentrations of cortisol to evaluate whether the circadian rhythm of cortisol secretion is also different in patients with CHD. Blood was collected by venous puncture at 0200 and at 1400, serum separated and kept frozen at -20 degrees C until analysis. Cortisol and melatonin were measured with a commercially available radioimmunoassay according to the instructions of the manufacturer. Nineteen patients with angiographically documented CHD (mean age 53 years) participated in this study. As control group served 12 adults without any signs of CHD. Melatonin serum concentrations (median; mean +/- SD) at night were significantly depressed in patients with coronary heart disease (7.8; 8.6 +/- 3.3 pg/ml) in comparison to the control group (38.0; 45.4 +/- 24.1 pg/ml) p < 0.01. Melatonin in the afternoon was not detectable in either of the groups. Cortisol values at night were significantly raised in patients with coronary heart disease (6.0; 7.2 +/- 3.7 mu g/dl) in comparison to the control group (2.7; 3.8 +/- 2.9 mu g/dl) p < 0.05. Cortisol levels in the afternoon were also elevated in patients with CHD (8.9; 9.5 +/- 3.8 mu g/dl) but there was no significant difference compared to controls (6.8; 6.9 +/- 4.5 mu g/dl). The results of the present study indicate that patients with coronary heart disease have atypical secretory patterns of nocturnal cortisol and melatonin secretion.