MAPK3 and cardiac hypertrophy: For example, testosterone activates the mTORC1/S6K1 axis through the IP3/Ca2+ and MEK/ERK1/2 signaling pathways to induce cardiac hypertrophy, and can induce cardiac hypertrophy through CaMKII-mediated activation of the downstream regulatory factor MEF2 (Altamirano et al., 2009; Duran et al., 2017).