The influence of smoking habits on thyroid gland volume: an ultrasonic approach.

The effects of smoking habits on thyroid function, echo-texture (nodules and/or cysts) and thyroid gland volume were determined by using ultrasound and measuring serum Thyroxin (T4), Triiodothyronine (T3), Thyrotropin (TSH) and TPO antibodies (ab-TPO) in 189 healthy smokers and non-smokers, randomly selected (111 females and 78 males) among the employees of our hospital and their relatives. When the entire group of subjects was considered the mean ratio of thyroid gland volume/body weight was found to be significantly higher in male (P < 0.05) and female (P < 0.05) smokers compared with non-smokers. In female smokers, mean serum thyroid-stimulating hormone (TSH) was lower (P < 0.05) and the degree of smoking was positively correlated with the ratio of thyroid gland volume/body weight (P < 0.05). However, when the subjects with a family history of goitre in first degree relatives were excluded from our study (14 females and 9 males), no significant differences in mean ratio of thyroid volume/weight or TSH between the remaining smokers and non-smokers were detected. In both sexes, the correlation between the degree of smoking and thyroid volume, although positive, did not reach statistical significance. No difference in prevalence of abnormal echogenicity and echo-texture (nodules and cysts) between smokers and non-smokers was detected. It is concluded that smoking habits present a goitrogenic effect only in subjects with a family history of goitre but have no influence on thyroid gland texture.