5-Iodo-1-oxaspiro[2.5]octa-4,7-dien-6-one is an intermediate in synthesizing 3,3',5-Triiodo-β-hydroxy-D/L-thyronine (T795305), which is an impurity or analog of 3,3’,5-Triiodo-D-thyronine (T795375), a structural analogue of the thyroidhormone Thyroxine (T425600). 3,3’,5-Triiodo-D-thyronine has been shown to reduce cholesterol in blood serum.