Smoking significantly increases risk for thyroid disease, particularly autoimmune Hashimoto’s thyroiditis and postpartum thyroiditis. Chemicals in cigarette smoke called thiocyanates appear to have especially harmful effects on the thyroid. Smoking also increases the negative effects of hypothyroidism, notably on the arteries and heart.
Cigarette smoking has multiple effects on thyroid function. These include both pro- (e.g. thyroidstimulating) and anti-thyroid actions and also actions that increase susceptibility to or exacerbation of the manifestations of Graves’ disease.
Tobacco smoke contains many chemicals, and its composition must vary substantially, depending on the source of the tobacco and the way it is smoked; and of course the amount smoked also varies substantially.
In a study involving women in Switzerland, Italy, the Netherlands and Sweden, it was found that smoking impairs both thyroid hormone secretion and thyroid hormone action, according to Beat Mueller, M.D., et al., in the October 12, 1995 issue of The New England Journal of Medicine.
The researchers, with the University Hospital in Basel, Switzerland, and other facilities, added that thyroid dysfunction and cigarette smoking are both common in the general population, with prevalence of about 10 percent and 30 percent respectively.
A reduced production of thyroid hormone leads to manifestations of thyroid insufficiency, including low metabolic rate, tendency to gain weight, sleepiness and often dryness and loss of hair, among other problems.
The consequences of smoking on thyroid size is however still controversial. It is accepted that an increase in serum thyiocyanate, a potent inhibitor of iodine transport, may contribute to the development of thyroid dysfunction, particularly in geographical areas with borderline iodine deficiency. In the general population, smoking is associated with normal thyroid hormone levels, with a tendency to lower TSH levels and enlargement of thyroid size. There is an increased risk of developing over thyroid disease.
