DAYTIME CIRCULATING MELATONIN LEVELS IN SMOKERS

Aims and background. Melatonin secretion is required to be a potential inhibitor of the development and growth of tumors, and cigarette smok ing is a well established risk factor for cancer at various sites. Met hods: Circulating melatonin levels of 20 smokers and 20 non smokers (c ontrols), sampled at the same hour from awaking in order to obtain a c omparable circadian synchronization, were compared. Results: Our data showed higher melatonin circulating levels in smokers (17.44 +/- 1.8 p g/ml) than in nonsmokers (9.77 +/- 1.4 pg/ml). Conclusions: The causes , mechanism and meaning of this phenomenon are still unknown. The most actractive hypothesis considers higher melatonin levels in smokers as an attempt to counter-balance cellular growth stimulus, a natural ''b rake'' mechanism to restrain the proliferation of normally differentia ted tissues: smoke is a prominent risk factor for several different tu mors.