Triiodothyronine: Molecular Structure and Biologic Function

Abstract

The active component of the thyroid gland, T₄, was the first hormone to be isolated and to have its structure characterized. Moreover, because the thyroid hormones possess relatively simple structures (Fig. 3.1), scientists were led to believe that their mode of action would be easily understood. However, although thyroid hormones have been shown to elicit a multitude of biologic responses, the specific nature of their actions remains unclear. Thus, the impetus to synthesize and test many analogues stemmed from the attempt to define those features essential for T₄-like activity.