Induction of Myxedema by Iodide in Patients Euthyroid after Radioiodine or Surgical Treatment of Diffuse Toxic Goiter

In all 10 patients with diffuse toxic goiter of Graves disease rendered euthyroid by radioiodine six months to six years earlier, myxedema (as evidenced by typical signs and symptoms, rises in serum TSH and cholesterol concentrations and decrease in serum thyroxine into the hypothyroid range) developed after small, pharmacologic doses of iodide. Of seven similar patients who had been treated surgically, frank hypothyroidism developed in two, one remained entirely unchanged, and the remaining four displayed slight abnormalities in serum thyroxine or TSH concentrations without overt hypothyroidism. The thyroid gland in Graves disease appears to be inherently susceptible to the induction of iodide myxedema, and such susceptibility may be enhanced or its demonstration facilitated by radioiodine treatment.