Influence of cigarette smoking on goiter formation, thyroglobulin, and thyroid hormone levels in women.

The possible influence of cigarette smoking on goiter formation, thyroglobulin (Tg) secretion, and thyroid hormone production was assessed by estimations of the presence of palpable goiter and by RIAs of Tg, T3, rT3, T4, and TSH in sera from 441 women (48-53 yr old), representing a normal population included in a study on the prevalence of thyroid disease. Smoking habits were evaluated by a questionnaire, and the women were then classified as never smokers (n = 192), smokers (n = 169), and exsmokers (n = 80). Smokers were subdivided as moderate (1-19 cigarettes/day) and heavy (greater than or equal to 20 cigarettes/day). Palpable goiter was found in 15% of the smokers, in contrast to only 4% of the exsmokers and 9% of the never smokers. Among smokers, 37% had serum Tg values over 30 micrograms/liter (third quartile), while such values were found in only 16% of the exsmokers and 18% of the never smokers. In addition, smokers were found to have higher serum T3 and lower rT3 concentrations than never smokers; this difference was most pronounced in heavy smokers. Serum T4 was not different, while TSH was insignificantly lower in smokers than in nonsmokers. Exsmokers did not differ significantly from never smokers in any of these parameters. It seems possible that cigarette smoking may have two, calorigenically opposed, effects on thyroid hormone production; it may be goitrogenic (possibly due to inhaled thiocyanate), but it may also enhance the formation of T3 at the expense of rT3 formation.