In 66 untreated patients with hyperthyroidism, serum triiodothyronine (T3) and thyroxine (T4) concentrations were measured by immunoassay. The mean T3 level was 478±28 ng/100 ml (all values mean±SEM) and the T4 was 20.6±0.6 μg/100 ml. The serum T4/T3 ratio by weight was 48±2 as opposed to a value of 71±3 in euthyroid adults. There was a significant inverse correlation of the T4/T3 ratios with serum T3 (r=0.77; P<0.01) but not with serum T4(r=0.21). These results suggested that relative overproduction of T3 is consistently present in patients with hyperthyroidism.
J. Abuid, P. R. Larsen