We made a clinical history of each subject and determined serum thyrotropin, antiperoxidase antibodies, urinary iodine
excretion and thyroid volume by ultrasonography. Subjects with thyroid disease were excluded. We finally studied 268 representative subjects. The reference thyroid volume was median 7.31 ml, mean 8.22 ml (Confidence Interval: 7.75-8.69 ml). In men: median 9.19 ml, mean 9.87 ml (CI: 9.09-10.65 ml); in women: median 6.19 ml, mean 6.57 ml (CI: 6.22-9.92 ml) (p<0.0001).