Alteration in diurnal and nocturnal melatonin serum level in patients with chronic heart failure.

INTRODUCTION Melatonin is best known for its influence on circardian physiology. The circulating levels of the hormone vary in a daily cycle, allowing the regulation of the circadian rhythms of several biological functions. Melatonin is now considered as a cardioprotective factor and its secretion might be influenced by the clinical course of CHF. OBJECTIVE Assessment of the alteration in diurnal and nocturnal melatonin serum levels in patients with chronic heart failure. MATERIAL AND METHODS The study group consisted of 32 patients diagnosed with CHF according to ESC criteria. The study group was divided into two subgroups: patients in NYHA class II (n=21, 8 women) and patients in NYHA class III (n=11, 6 women). In all patients, serum melatonin levels at 02:00 and at 07:00 were determined using competitive enzyme immunoassay technique. High-sensitive C-reactive protein (HsCRP) was determined with nephelometric method. RESULTS Mean hsCRP level was 0.368 (0.195; 0.794) mg/l and 0.54 (0.128; 1.04) mg/l in the group NYHA II and NYHA III patients, respectively; the difference was not statistically significant. NTproBNP levels were higher in NYHA III group than in the group NYHA II [2300 (1509;6317) pg/ml vs 7157 (4155; 13339) pg/ml]; the difference was substantial and approached the level of statistical significance (p=0.057). In both subgroups, higher levels of melatonin at 02:00 than at 07:00 was noticed; however, the differences were not statistically significant (p>0.05). In NYHA III subgroup lower levels of melatonin were observed at both time points; the difference was not statistically significant. CONCLUSION The study results suggest that in patients with advanced heart failure (NYHA III but not NYHA II), nocturnal melatonin secretion is negatively correlated with NTproBNP.