question: How does dronedarone affect thyroid hormone signaling in the heart?
answer: Dronedarone via its metabolite debutyldronedarone acts as a TRalpha(1)-selective inhibitor and selectively mimicks hypothyroidism.
  Dronedarone  decreases TRalpha 1 and beta 1 expression by about 50%  in the right atrium (RA)  while in the left ventricle, only TRbeta1 is found to be decreased.