High frequency of goitre in cigarette smokers

Thyroid function, the clinical occurrence of goitre and ultrasonically determined thyroid gland volume were investigated in 219 healthy subjects randomly chosen from hospital employees. Thirty-five subjects (16%) had a clinically detectable goitre. The frequency of goitre among smokers was higher (32 of 107, 30%) than among non-smokers (3 of 112, 3%), (P less than 0.001). Median thyroid volume was significantly higher in smokers, 26 ml (range 11-55 ml), compared with non-smokers, 15 ml (range 8-37 ml), (P less than 0.001). The median serum thyroglobulin levels were significantly higher and median serum thyrotropin levels lower in smokers compared with non-smokers. There were no differences between the groups regarding serum levels of T4, T3, rT3, free T4 index, free T3 index, thyroglobulin antibodies and 131I uptake (24 h) in the thyroid gland. It is suggested that these findings could partly be due to inhaled thiocyanate and/or increased adrenergic stimulation of the thyroid gland in smokers.