[Restitution of the thyrotropic function in goiter patients after discontinuing a long-term suppression therapy with...

27 subjects with a negative TRH test were selected among patients with euthyroid goiter treated by thyroid hormones. The hormone therapy was stopped and T3 and T4 concentrations, basal and TRH stimulated TSH levels were determined after one, two and four weeks. A gradual increase of the mean basal and TRH stimulated TSH plasms concentration could be observed. However, after four weeks the TRH test was still negative in two patients and weak positive in another case. T3 plasma levels were lowest after one week which might indicate the presence of an intermittent thyrotropic insufficiency. It is concluded that the hormone-free interval should last four weeks at least before a reliable TRH test can be obtained.