Evolving concepts of thyroid hormone action.

The past 25 years have witnessed dramatic changes in our concepts of thyroid hormone action. Progress in this area was made possible by the recognition of the central role of triiodothyronine in mediating thyroid hormone action and the recognition of specific nuclear receptors in target tissues as demonstrated by displacement studies. The cloning of the receptors and receptor variants has enabled investigators to undertake detailed analyses of the biochemical events which underlie the physiological and pathological action of thyroid hormone.