Discontinuation of smoking increases the risk for developing thyroid peroxidase antibodies and/or thyroglobulin antibodies: a prospective study.
BACKGROUND
Autoimmune thyroid disease develops in genetic susceptible subjects, provoked by environmental factors. Little is known of the environment in the early stages of autoimmunity.


OBJECTIVE
We evaluated environmental factors contributing to de novo occurrence of thyroid antibodies.


METHODS
We conducted a prospective cohort study of 521 euthyroid women without thyroid antibodies in serum who were relatives of autoimmune thyroid disease patients. Follow-up was 5 yr. Baseline characteristics were related to the occurrence of thyroid peroxidase (TPO) and/or thyroglobulin (Tg) antibodies. Exposure to environmental factors in the year prior to the occurrence of antibodies was investigated in a nested case-control study.


RESULTS
The 5-yr probability for conversion to TPO antibodies (TPO-Ab) and/or Tg antibodies (Tg-Ab) was 20.1%, and for TPO-Ab alone the probability was 14.5%. None of the baseline characteristics except TSH contributed to the risk of seroconversion. Each case (occurrence of antibodies) was matched for age and duration of follow-up with two controls (no seroconversion). Exposure to environmental stimuli was similar between cases and controls except for smoking. At study entrance, current smokers among cases and controls were 31.3 and 35.5%, respectively (nonsignificant). Current smoking decreased in cases during follow-up. Consequently, the odds ratios (OR) of smoking for developing TPO-Ab and/or Tg-Ab were 0.62 [95% confidence interval (CI), 0.37-1.04] 1 yr before seroconversion and 0.59 (95% CI, 0.35-0.99) at seroconversion; for conversion to TPO-Ab, these figures are 0.58 (95% CI, 0.31-1.09) and 0.54 (95% CI, 0.29-1.02), respectively.


CONCLUSIONS
Discontinuation of smoking is associated with an increased risk for occurrence of TPO-Ab and/or Tg-Ab in serum. The observation is in line with the decreased risk of hypothyroidism in smokers.
Effraimidis
Grigoris
G
Department of Endocrinology, Academic Medical Center, Amsterdam, The Netherlands.
Tijssen
Jan G P
JG
Wiersinga
Wilmar M
WM
D000293:Adolescent; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D015331:Cohort Studies; D005190:Family; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007453:Iodide Peroxidase / Q000276:immunology*; D008875:Middle Aged; D011336:Probability; D011446:Prospective Studies; D012016:Reference Values; D012907:Smoking / Q000097:blood / Q000276:immunology; D016540:Smoking Cessation / Q000706:statistics & numerical data*; D013967:Thyroiditis, Autoimmune / Q000235:genetics; D055815:Young Adult
D001323:Autoantibodies; C006606:anti-thyroglobulin; D005640:Follicle Stimulating Hormone; D007453:Iodide Peroxidase