Syndrome of persisting thyroid stimulating immunoglobulins and growth promotion of goiter combined with low thyroxine and high triiodothyronine serum levels in drug treated Graves' disease.

Among 48 Graves' patients treated with antithyroid drugs there were 8 patients with a further growth of an already enlarged goiter and a persistence of thyroid stimulating immunoglobulins (TSI). TSI activity did not persist in a comparison group of patients with less severe initial symptoms and an uncomplicated course during a similar regimen of drug treatment. Thyrotoxicosis was difficult to control in this subgroup of patients as low serum T4 was accompanied by borderline high T3 levels although TSH in serum remained undetectable. In spite of comparable low doses of antithyroid drugs serum T4 in the complicated group remained significantly lower (58 +/= 15 nmol/I SD vs. 97 +/- 19 nmol/I SD, p less than 0,001) and serum T3 stayed significantly higher (3,66 +/- 0,49 nmol/I SD vs. 2,15 +/- 0,50 nmol/I SD, p less than 0,001) than in the group with uncomplicated treatment. It is discussed that the promotion of goiter growth could be due to growth stimulating antibodies, and that a local intrathyroidal iodide depletion during antithyroid drug treatment might cause the shift from T4 to T3 production in this entity of Graves' patients.