Thyroid stimulating immunoglobulins in Graves' disease with goitre growth, low thyroxine and increasing triiodothyronine during PTU treatment

In 50 consecutive patients with Graves' disease treated with PTU, 7 (group 1) developed increasing goitre in spite of unmeasurable TSH. Thyroid variables were compared with those from 10 controls with an ordinary response to PTU (group 2). Serum T4 decreased in group 1 from 246 +/- 47 nmol/l (mean +/- SD) to 40 +/- 9 nmol/l after 6 weeks of PTU treatment and continued to be below the normal range during the next 4 months. In group 2 serum T4 decreased from 190 +/- 35 to 88 +/- 47 nmol/l and stayed in the normal range. Serum T3 was normalized in both groups after 6 weeks but increased to values above the normal range in group 1 after that time. In spite of unmeasurable TSH during the 6 months of treatment in group 1, thyroid volume, determined ultrasonically, increased significantly from 60 +/- 29 to 93 +/- 68 ml (P less than 0.05), but was unaltered in group 2 about 25 ml. Thyroid stimulating antibodies (TSAb) measured by adenylate cyclase activation (normal below 109%) decreased in group 2 from 117 +/- 23 to 90 +/- 17% (P less than 0.01) (6 months of therapy), but increased significantly in group 1, from 201 +/- 47% to a maximum value of 234 +/- 69% (P less than 0.05). TSH binding inhibitory immunoglobulins (TBII) (given as per cent inhibition, normal below 26%) decreased in group 2 from 43 +/- 29 to 29 +/- 27% (P less than 0.05) but were unaltered high in group 1, 66 +/- 25% before therapy and 57 +/- 26% after 6 months of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)