Hyperthyroid Crisis-Reply

Abstract

In Reply.— We thank Doctors Green and Graham for their comments. Although the total body pool of thyroxine is approximately 500μg to 800μg, we have been reluctant to give a comatose patient more levothyroxine sodium than 200μg to 250μg as an intravenous bolus because of the disposal rate of thyroxine which is about 10% in 24 hours and the possibility of an accumulation of the hormone. We have had a few patients in whom cardiac arrhythmias developed at higher doses, which, of course, may also have occurred had lower doses been administered. This is interesting, as we have not encountered problems with relatively higher doses of liothyronine sodium. The responses probably reflect different disposal rates and patient sensitivity to thyroxine and triiodothyronine (T 3 ). As thyroxine probably does have biological activity not dependent on conversion to T 3 , 1 the more prolonged exposure to levothyroxine after high intravenous dosage may