Function of thyroid and hypotalamic-pituitary-thyroid axis in radioiodine treated thyrotoxic patients.

We examined 431 thyrotoxic patients at varying intervals after therapy with radioactive iodine--131I. Recidives of thyrotoxicosis were noted in 30 patients (7%), hypothyroidism in 63 patients (14.4%) and the remaining 338 were euthyroid. A peculiar clinical picture of postradiation hyperthyroidism was ascertained. The euthyroid patients had a lower protein bound iodine (PBI) concentration than normal individuals (4.9 +/- 1.7, resp., 6.0 +/- 1.64 mg/100 ml) and a negative thyroid response after the thyrotrophin-releasing hormone (TRH) stimulation in 87 per cent.