Response to thyrotrophin-releasing hormone and triiodothyronine suppressibility in euthyroid multinodular goitre

In twenty-two female patients with euthyroid multinodular goitre of varying size, thyroid suppression of 131I thyroid uptake by triiodothyronine (T3) and thyrotrophin (TSH) release after thyrotrophin-releasing hormone (TRH) administration were compared with thyroid weight, estimated by a planimetric method, and with serum thyroxine (T4) and T3 concentrations. Maximal increment of TSH (deltaTSH) after TRH and per cent T3-suppressibility were inversely related to thyroid weight and not related to basal serum T4 or T3 concentrations. deltaTSH and per cent suppression correlated positively, but deltaTSH was more often subnormal than T3-suppressibility. A practical consequence of our study is that nonconformity of the two tests may occur. This should be kept in mind in the evaluation of patients with thyroid disorders.