Thyroid Hormone Action in the Heart

The heart is a major target organ for thyroid hormone action, and marked changes occur in cardiac function in patients with hypo-or hyperthyroidism. T 3 -induced changes in cardiac function can result from direct or indirect T 3 effects. Direct effects result from T 3 action in the heart itself and are mediated by nuclear or extranuclear mechanisms. Extranuclear T 3 effects, which occur independent of nuclear T 3 receptor binding and increases in protein synthesis, influence primarily the transport of amino acids, sugars, and calcium across the cell membrane. Nuclear T 3 effects are mediated by the binding of T 3 to specific nuclear receptor proteins, which results in in-creased transcription of T 3…

• UO
  University of California, San Diego