Smoking and the thyroid

Smoking has a goitrogenic effect, especially in iodine-deficient areas, although it might have a protective effect against differentiated thyroid cancer. In genetically susceptible individuals, smoking is associated with a higher risk of new-onset or relapse of hyperthyroidism due to Graves’ disease. Furthermore, Graves’ patients who smoke are at much higher risk of developing Graves’ orbitopathy, particularly in its severe forms, and of a lower/delayed response to immunosuppressive treatments for this extrathyroidal manifestation of Graves’ disease. At variance, smoking may have a protective effect on the development of chronic autoimmune thyroiditis and related hypothyroidism.