Circadian rhythm of melatonin in patients with colorectal carcinoma.

OBJECTIVE The aim of the study was pineal gland function assessment on the base of daily rhythm study and mean daily melatonin (MEL) concentrations in serum in patients with colorectal carcinoma. MATERIAL AND METHODS Studies were performed in 12 women at the age of 63.17+/-5.90 years and 21 men aged 58.95+/-11.32 years with large intestine adenocarcinoma. The control group consisted of 28 healthy volunteers at comparable age. During the circadian study blood samples for the measurement of melatonin (MEL) were collected every 4 hours during 12 h. MEL concentrations were assessed with the use of RIA methods. Statistical analysis of circadian rhythms of MEL was carried out with the use of cosinor method according to Halberg. RESULTS Existence of daily rhythm of MEL secretion was shown in all studied groups. A significant decrease of amplitude of rhythm and secretion of MEL at nocturnal hours in comparison with the control group was shown in the group of women with large intestine carcinoma. A significant decrease of mesor value and amplitude of MEL rhythm as a consequence of decrease of MEL secretion at nocturnal and morning hours was observed in the group of ill men. CONCLUSIONS Decrease in melatonin circadian rhythm amplitude as a consequence of its lowered nocturnal secretion occurred in all patients with colorectal carcinoma. Abnormalities in daily rhythm of melatonin secretion were more intensified in men with large intestine carcinoma, which leads to suppression of mean daily hormone concentration.