Thyroid hormone (TH) appears to have a critical role in cardiac repair after injury beyond its role in development and metabolism homeostasis. This unique action is due to the fact that TH effect on the heart is shown to be differentiated depending on its administration on injured or healthy myocardium. Thus, TH can limit ischemia-reperfusion injury via a fine balance between pro-apoptotic and pro-survival signaling pathways. This response is thyroid hormone receptor (TRα1) dependent. Furthermore, an interaction between stress-induced growth kinase signaling and TRα1 is shown to occur and determine postischemic remodeling and cardiac recovery depending on the availability of TH. This new evidence is consistent with clinical observations showing the cardioprotective effect of TH treatment in cardiac surgery, transplantation and heart failure. TH and/or thyroid analogs may be novel agents in treating heart diseases.