Role of smoking in goiter morphology and thyrotropin response to TRH in untreated goitrous women.

Three groups of women were evaluated for TSH response to TRH and for goiter morphology by means of thyroid ultrasonography: group A = goitrous nonsmokers; group B1 = goitrous moderate-smokers; group B2 = goitrous heavy-smokers. They were compared with a control group (group C) made up nongoitrous, nonsmoking women. The size of the goiter was not correlated with the daily consumption of cigarettes, even though in heavy smokers a nodular goiter was prevalent as shown by ultrasonography. The serum values of TT3 showed significant differences between nonsmokers and heavy smokers (p less than (p less than 0.005), whereas the serum values of TT4 and of basal TSH showed no statistically significant differences. On the contrary, the TSH response to TRH showed a significant difference between heavy and nonsmokers (p less than 0.05). In conclusion, it has been demonstrated that goitrous cigarette heavy smokers show: i) A prevalence of statistically significant nodular goiter; ii) A significantly higher TT3 serum levels; iii) A significantly higher re-of TSH to TRH. These data suggest that cigarette smoking favors the development of nodular goiter and can involve the central regulation of the hypothalamus-pituitary-thyroid interaction.