TH and hyperthyroidism: To sum up, our results show that hyperthyroidism decreases EFS-induced vasoconstriction through: (1) a diminished sympathetic response due to a lower expression of TH and DβH, leading to a blunted NA synthesis and release; (2) a decreased purinergic neurotransmission; and (3) an increase in NO release from nitrergic nerve endings, through augmented nNOS activation due to nNOS hyperactivation of the PI3K-AKT and PKC pathways.