One in five subjects with normal thyroid ultrasonography has altered thyroid tests.

The relation between thyroid ultrasonography and laboratory, and the relationship of thyroid volume with clinical and anthropometric parameters, are not well clarified. Aim of the study was to investigate normal and hypoechoic-inhomogeneous not nodular thyroid gland in predicting thyroid tests, and to assess the correlation of thyroid volume with several clinical parameters. The series included 434 subjects (244 with normal thyroid ultrasonography, and 190 with hypoechoic-inhomogeneous thyroid) at their first evaluation. Subjects with normal ultrasonography and skewed tests were re-evaluated after one year. All subjects with normal ultrasound showed normal free-T₄, while TSH was elevated in 9.8% of cases and thyroid antibodies were positive in another 9.8%. In patients with hypoechoic-inhomogeneous thyroid, free-T₄ was low in 33.2%, TSH was elevated in 78.4% and thyroid antibodies were positive in 76.3%. Normal ultrasonography matched with normal tests in 81.1% of cases while hypoechoic-inhomogeneous thyroid in 9.5% (p<0.001). The re-evaluation of tests showed no significant difference. In subjects with both normal ultrasonography and tests, thyroid volume was correlated with age (p=0.001), weight (p=0.003), BMI (p=0.04), body surface area (p=0.002). Thyroid laboratory assessment was different between subjects with ultrasonographically normal or hypoechoic-inhomogeneous thyroid. Thyroid volume of thyroid diseases-free subjects was correlated with age, weight, BMI and body surface area, and this should be of interest to investigate the references of normality of thyroid size.