The thyroxine-like activity of compounds structurally related to thyroxine.

In the course of a search for compounds which might prove to be competitive inhibitors of thyroxine in its action on the peripheral tissues, we have initiated a study of the relationship between chemical structure and thyroxine-like activity of a number of thyroxine analogues. Early attempts to relate chemical constitution to physiological activity have been summarized by Harington (1, 2) who concluded that the structural requirements for activity were best represented by (I), where X is a