Inhibition of thyroid monoamineoxidase by thyroxine and some specific inhibitors

Rat thyroid monoamine oxidase (MAO) was inhibited by the non-hydrazine derivatives paragyline and tranylcypromine to a higher degree than the hydrazine derivative iproniazide. MAO was also inhibited by monoiodotyrosine and thyroxine. These results indicate that MAO may be an important enzyme in the metabolism of biogenic amines, iodotyrosines and tyronines in the thyroid gland.