The T3 suppression test was used in the past to demonstrate thyroid autonomy. A radioiodine uptake test is repeated after the patient has taken a suppressive dose of T3 (at least 20┬╡g/tid for one week). In normal individuals, radioiodine uptake is suppressed to at least fifty per cent of the pretreatment value. Failure of suppression occurs in thyrotoxicosis and in patients with autonomous ΓÇÿhotΓÇÖ nodules. The test is seldom necessary now, and the addition of T3 can be dangerous to patients who are already hyperthyroid.
