Non-palpable thyroid nodules in a borderline iodine-sufficient area: detection by ultrasonography and follow-up.

Thyroid ultrasonography was performed in 482 subjects, free of known thyroid disease and living in a borderline iodine-sufficient urban area, to assess the prevalence of non-palpable thyroid nodules and evaluation their evolute during a 3-yr follow-up. The mean (+/-SD) thyroid volume in the whole study group was 10.9+/-3.7 ml and was higher in males (12.9+/-3.6 ml) than in females (9.2+/-2.9 ml) (p<0.0001). Thyroid volume was correlated with body surface, height and weight, while no correlation was present with lean and fat body mass. Goiter was found in 5/256 females and in 13/226 males. Thyroid nodules were found in 27/482 subjects (18 females, 9 males). Single nodules were found in 17/464 subjects (3.66%) with a thyroid gland of normal volume and in 4/18 subjects (22.2%) with goiter (chi2=10.21; p=0.001). Multiple nodules were found in 3/464 subjects (0.6%) with a thyroid of normal volume and in 3/18 (16.6%) subjects with goiter (chi2=24.31; p<0.0001). The prevalence of thyroid nodules was significantly higher in females >35 yr than in those <34 yr (chi2=7.47; p=0.0062). A significant increase (>30%) of nodular volume was found in 5 subjects, while an increased number of nodules was found in 8. In conclusion, thyroid ultrasonography reveals the presence of thyroid nodules in a significant proportion of apparently thyroid disease-free subjects living in a borderline iodine-sufficient urban area. Incidentally discovered thyroid nodules are associated with goiter and are likely to progress in volume and number.