Smoking and Graves Disease

Posted by Elaine Moore Jul 16, 2007

Cigarette smoking is similar to iodine in that it has been shown to both inhibit and stimulate thyroid function, triggering both autoimmune hypothyroidism and autoimmune hyperthyroidism. However, based on data from the Third National Health and Nutrition Examination Survey (NHANES III), cigarette smoke is more often associated with hyperthyroidism than hypothyroidism and is a known risk factor for both Graves’ disease and thyroid eye disease (Graves' ophthalmopathy).

The NHANES Study

Subjects in the study included 16, 046 people ranging from 12-90 years in age. Results of these subjects used to determine the effects of smoke exposure included: demographic, smoke exposure, urinary iodide, serum TSH level, thyroid peroxidase (TPO) antibody levels and thyroglobulin antibody levels. Smoking or smoke exposure was determined by measuring levels of serum cotinine, one of the major long-lasting metabolites of nicotine. High levels of TPO and thyroglobulin antibodies are seen in Hashimoto’s thyroiditis, whereas low levels are seen in about 80 percent of people with Graves’ disease. The study did not include measurement of stimulating TSH receptor antibodies, the antibodies that cause hyperthyroidism in Graves’ disease.

Study Results

Among the 16, 046 participants, 5134 were found to be active smokers based on their cotinine levels. The smokers had a mean age of 40 years. More men than women were active smokers, and the smokers were more often white or black than Hispanic or Asian. Compared with the non-smokers, fewer smokers (3.4 percent) had TSH levels higher than 4.5 mU/L. Other factors, however, were associated with a high TSH level, including increasing age, female sex, white or Hispanic race-ethnicity and higher urinary iodide excretion. Of the non-smokers, 5.4 percent had elevated TSH levels.

In non smokers, 0.6 percent had TSH levels less than 0.1 mU/L compared to 0.3 percent in nonsmokers. 11 percent of smokers had elevated TPO or thyroglobulin antibody levels compared to 18 percent of nonsmokers.

Thyroid Eye Disease

Patients with Graves’ disease who smoke are reported to have a 4-14 fold increase in thyroid eye disease. It’s suspected that the chemicals in smoke that circulate over thyroid cells stimulate the production of TSH receptor antibodies. High levels of TSH receptor antibodies are associated with an increased risk of thyroid eye disease.

Resources:

Belin RM, Astor BC, Powe NR, and Ladenson PW, Smoke exposure is associated with a lower prevalence of serum thyroid autoantibodies and thyrotropin concentration elation and a higher prevalence of mild thyrotropin concentration suppression in the Third National Health and Nutrition Examination Survey (NHANES III), Journal of Clinical Endocrinology and Metabolism 2004l 89: 6077-6086.