RETN and major depressive disorder: Resistin was found to induce a significant inhibition of dopamine and noradrenaline synthesis in the hypothalamus [74], suggesting that the activation of the resistin cell-signaling system on target neurons [24] and on Th1-immune cells [75] exerts an influence on catecholaminergic neural pathways [74] and, hence, on the neural mechanisms implicated in major depression [63,64].