Normal conversion of thyroxine to triiodothyronine in a subject with iodotyrosine-dehalogenase deficiency.

BMR, t1/2 of serum T4, and the conversion of T4 to T3 were normal in a patient with iodotyrosine-dehalogenase deficiency who had undergone total surgical thyroidectomy and had been maintained on 200 mug of oral T4 daily. It is concluded that the enzyme system for monodeiodination and conversion of T4 to T3 is different than iodotyrosine-dehalogenase.