Smoking and thyroid disorders--a meta-analysis.
BACKGROUND
Smoking has been associated with Graves' disease, but it remains unclear if the association is present in other thyroid disorders.


METHODS
Graves' disease, Graves' ophthalmopathy, toxic nodular goitre, non-toxic goitre, post-partum thyroid disease, Hashimoto's thyroiditis, or hypothyroidism.


METHODS
A search of MEDLINE identified 25 studies on the association between smoking and thyroid diseases.


RESULTS
In Graves' disease eight studies were available showing an odds ratio (OR) of 3.30 (95% confidence interval (CI): 2.09-5.22) in current smokers compared with never smokers. In ex-smokers there was no significant excess risk of Graves' disease (OR=1.41, 95% CI: 0.77-2.58). The OR associated with ever smoking in Graves' ophthalmopathy (4.40, 95% CI: 2.88-6.73, six studies) was significantly higher than in Graves' disease (1.90, 95% CI: 1.42-2.55, two-sided P-value <0.01). Ever smoking was not associated with toxic nodular goitre (OR=1.27, 95% CI: 0.69-2.33, three studies), while there was an increased risk of non-toxic goitre in smokers if men were excluded (OR=1.29, 95% CI: 1.01-1.65, eight studies). The risk associated with smoking was significantly lower in men than in women for both Graves' disease and non-toxic goitre. Hashimoto's thyroiditis and post-partum thyroid dysfunction were also associated with smoking while the association with hypothyroidism did not reach statistical significance.


CONCLUSIONS
Cessation of smoking seems associated with a lower risk of Graves' disease than current smoking. Smoking increases the risk of Graves' ophthalmopathy beyond the risk associated with Graves' disease alone. Smoking cessation may lead to a decrease in morbidity from Graves' disease, especially in women.
Vestergaard
Peter
P
The Osteoporosis Clinic, Aarhus Amtssygehus, Aarhus University Hospital, Tage Hansens Gade 2, DK-8000 Aarhus C, Denmark. p-vest@post4.tele.dk
D005260:Female; D006042:Goiter / Q000453:epidemiology / Q000209:etiology; D006111:Graves Disease / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D007037:Hypothyroidism / Q000453:epidemiology / Q000209:etiology; D016239:MEDLINE; D008297:Male; D016017:Odds Ratio; D011644:Puerperal Disorders / Q000453:epidemiology; D012727:Sex Characteristics; D012907:Smoking / Q000009:adverse effects*; D013959:Thyroid Diseases / Q000453:epidemiology / Q000209:etiology*; D013967:Thyroiditis, Autoimmune / Q000453:epidemiology / Q000209:etiology