Potency (EC₅₀ and IC₅₀) values were calculated from full dose response curves in the absence and presence of T₃ (1nM), respectively. Efficacy was defined as percentage of maximal induction (agonist mode) or inhibition (antagonist mode) relative to T₃ set at 100% (100 nM for testing of agonist and 1 nM for antagonist activity).