Abstract

Three series of patients shown to be euthyroid but originally referred for thyroid uptake tests in vivo have been compared.

In 1958-59, the `normal' mean thyroid uptake was 23·5% and 38·2% respectively at four and 24 hours. By 1967, the mean uptakes had dropped to 20·4% and 31·6%—a significant change at both times. By 1972 there was, however, no sign of a further reduction of the mean normal values for thyroid uptake.

These results are compared with changes observed in other series in the USA and elsewhere.