Abstract
SUMMARY: The triiodothyronine (T3):thyroxine (T4) radioactive iodine ratio in the blood of six thyrotoxic and twelve thyroid cancer patients was measured radiochemically by means of two-dimensional paper chromatography and a low-level counter. The ratio was found to be 0·046 (with a standard error of 0·004). No significant difference was found between the two groups of patients. When the binding properties of these thyroid hormones to the serum protein are considered, the contribution of T3 to the metabolic effect is estimated to be one half of that of T4 in the patients studied.