title: Daytime circulating melatonin levels in smokers.
abstract: OBJECTIVE
  Melatonin secretion is required to be a potential inhibitor of the development and growth of tumors, and cigarette smoking is a well established risk factor for cancer at various sites.
  
  
  METHODS
  Circulating melatonin levels of 20 smokers and 20 non smokers (controls), sampled at the same hour from awaking in order to obtain a comparable circadian synchronization, were compared.
  
  
  RESULTS
  Our data showed higher melatonin circulating levels in smokers (17.44 +/- 1.8 pg/ml) than in nonsmokers (9.77 +/- 1.4 pg/ml).
  
  
  CONCLUSIONS
  The causes, mechanism and meaning of this phenomenon are still unknown. The most attractive hypothesis considers higher melatonin levels in smokers as an attempt to counterbalance cellular growth stimulus, a natural "brake" mechanism to restrain the proliferation of normally differentiated tissues: smoke is a prominent risk factor for several different tumors.
authors.affiliation: Cattedra di Medicina Interna I, University of Florence, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Tarquini
authors.forename: F
authors.initials: F
authors.lastname: Perfetto
authors.forename: R
authors.initials: R
authors.lastname: Poli
authors.forename: R
authors.initials: R
authors.lastname: Tarquini
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000097:blood*; D008875:Middle Aged; D012907:Smoking / Q000097:blood*; D013997:Time Factors
chemical_list: D008550:Melatonin