[Biological changes in 88 cases of Basedow's disease treated by radioactive iodine].

Biological abnormalities, in particular increased T3 and sometimes TSH, are frequently found in thyrotoxic patients treated with radioactive iodine and subsequently enthyroid. A high T3, associated with an increase in FT4 and a low TSH precedes a relapse. An increase in TSH may indicate progression towards hypothyroidism; even if FT4 and T3 levels are within normal limits. Caution must be exercised before affirming that an increased TSH with a high T3 and normal FT4 is indicative of thyroid equilibrium. At all events, the risk of hypothyroidism despite the use of small doses of radioactive iodine is such that the classical limit for the treatment of patients with thyrotoxicosis should be increased beyond the age of 40. In patients with a high TSH despite being clinically euthyroid, the use of thyroid extract in low dosage (50 mg/day) would appear to be desirable in avoiding the subsequent development of hypothyroidism.