Association of thyroid-stimulating immunoglobulins and thyrotropin-releasing hormone responsiveness in women with euthyroid goiter.

Thyroid-stimulating immunoglobulins (TSI) were measured, using a highly sensitive cytochemical bioassay, in plasma from 26 euthyroid women with idiopathic diffuse or multinodular goiter selected on the basis of their serum TSH responses to TRH stimulation. Thirteen were chosen because they were previously identified to have impairment in TRH responsiveness and were compared with 13 consecutive patients who had normal responses to TRH. TSI were present in a significantly greater number of those who had subnormal TRH responses (11:13) compared to those who had normal responses (3:13) P less than 0.005. Although serum T4, T3, and basal TSH values were all within the normal range, mean serum T4 and T3 values were significantly higher and basal TSH significantly lower in the 14 patients who had TSI than in the 12 in whom TSI was absent. The coexistence of impaired TRH responsiveness and TSI was associated with a family history of thyroid disease. The data suggest that TSI in patients with euthyroid goiter cause a modest increase in thyroid secretion sufficient to blunt the TSH response to TRH but not to cause clinical hyperthyroidism.