An efficient and scalable preparation of the thyroid hormone analogue O-[3-iodo-4-(sulfooxy)phenyl]-3,5-diiodo-l-tyrosine sodium salt (T3-sulfate, 1) is reported. The synthesis involved monoiodination of O-(4-hydroxyphenyl)-3,5-diiodo-l-tyrosine to give liothyronine (2) which was sulfated with chlorosulfonic acid in N,N-dimethylacetamide. Crude T3-sulfate was initially purified by chromatography on