title: A cautious iodization programme bringing iodine intake to a low recommended level is associated with an increase in the prevalence of thyroid autoantibodies in the population.
abstract: Autoantibodies against the thyroid gland with thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (Tg-Ab) as the most common can often be demonstrated in serum. The effect of public iodization programmes on antibody prevalence is uncertain.
  
  
  OBJECTIVE
  To measure the concentrations of thyroid autoantibodies in the Danish population before and after mandatory iodization of salt.
  
  
  METHODS
  Two identical cross-sectional population studies were performed before (Cohort 1 (C1), year 1997-1998, n = 4649, median urinary iodine 61 μg/l) and 4-5 years after (Cohort 2 (C2), year 2004-2005, n = 3570, median urinary iodine 101 μg/l) mandatory iodine fortification of salt was implemented in Denmark. Blood tests were analysed for TPO-Ab and Tg-Ab using sensitive assays.
  
  
  RESULTS
  Antibodies were more frequent in C2 than in C1: TPO-Ab > 30 U/ml, C1 vs C2: 14·3 vs 23·8% (P < 0·001) and Tg-Ab > 20 U/ml, C1 vs C2: 13·7 vs 19·9% (P < 0·001). The C2 vs C1 effect was confirmed in multivariate regression models (C1 reference): TPO-Ab: OR (95% CI): 1·80 (1·59-2·04) and Tg-Ab: 1·49 (1·31-1·69). The increase in the frequency of thyroid antibodies was most pronounced in young women and especially observed at low concentrations of antibodies.
  
  
  CONCLUSIONS
  The prevalence of both TPO-Ab and Tg-Ab was higher 4-5 years after a cautious iodine fortification of salt was introduced in Denmark. The increase was most pronounced in young women and in the low concentrations of antibody. Further studies are needed to evaluate the long-term effects of increased iodine intake on thyroid autoimmunity in the population.
authors.affiliation: Department of Endocrinology and Medicine, Aalborg Hospital, Aarhus University Hospital, AalborgEndocrine Unit, Medical Clinic I, Bispebjerg Hospital, CopenhagenResearch Centre for Prevention and Health, Glostrup University Hospital, GlostrupFaculty of Health Science, University of Copenhagen, CopenhagenDepartment of Gastroenterology, Slagelse Hospital, SlagelseDivision of Nutrition, National Food Institute, Copenhagen, Denmark.
authors.forename: Inge B
authors.initials: IB
authors.lastname: Pedersen
authors.forename: Nils
authors.initials: N
authors.lastname: Knudsen
authors.forename: Allan
authors.initials: A
authors.lastname: Carlé
authors.forename: Pernille
authors.initials: P
authors.lastname: Vejbjerg
authors.forename: Torben
authors.initials: T
authors.lastname: Jørgensen
authors.forename: Hans
authors.initials: H
authors.lastname: Perrild
authors.forename: Lars
authors.initials: L
authors.lastname: Ovesen
authors.forename: Lone B
authors.initials: LB
authors.lastname: Rasmussen
authors.forename: Peter
authors.initials: P
authors.lastname: Laurberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000276:immunology*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007453:Iodide Peroxidase / Q000276:immunology*; D007455:Iodine / Q000008:administration & dosage / Q000494:pharmacology*; D033862:Iron-Binding Proteins / Q000276:immunology*; D008297:Male; D037141:Mandatory Programs / Q000706:statistics & numerical data; D008875:Middle Aged; D009752:Nutritional Status; D015995:Prevalence; D012737:Sex Factors; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000494:pharmacology*; D013954:Thyroglobulin / Q000276:immunology*; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D033862:Iron-Binding Proteins; D017673:Sodium Chloride, Dietary; C034024:iodized salt; D013954:Thyroglobulin; D007455:Iodine; C056658:TPO protein, human; D007453:Iodide Peroxidase