Purpose: The objective of this study was to determine the cardiac gene expression prifile in the whole heart of mice with mutated thyroid receptor alpha 1 (TRα1R384C+/m) in control condition as well as after treatement with 3,3´,5-triiodo-L-thyronine (T3) for 12 days. Overall design: Methods: 3-6 month old wildtype (n=12) and TRα1R384C+/m (n=10) male mice were housed at 30°C with ad libitum access to drinking tap water containing T3 (0.5 mg/L) for 12 days. Control groups had ad libitum access to drinking tap water. All four groups had ad libitum access to chow food.