Daily excretion of melatonin in patients with cancer of the stomach and large intestine

Diurnal excretion of melatonin was studied in 37 cases of gastric and rectal cancer. In cancer patients nocturnal excretion was lower than in daytime while in healthy subjects the situation was reversed. Increased extrapineal production of melatonin as a possible cause of disorders in its excretion rhythm is discussed.