Other physiological studies have demonstrated that Mct8-deficient mice present a state of brain hyperthyroidism from E18 until P5 and that the combined inactivation of Mct8 and Lat2 suppresses this hyperthyroidism (Ferrara et al., 2013; Núñez et al., 2014) suggesting a crucial role for TH transporters in brain TH homeostasis. This evidence concerns the gene TH and hyperthyroidism.