Membrane steroid receptors (mSRs), also called extranuclear steroid receptors, are a class of cell surface receptors activated by endogenous steroids that mediate rapid, non-genomic signaling via modulation of intracellular signaling cascades.[1][2][3][4] mSRs are another means besides classical nuclear steroid hormone receptors (SHRs) for steroids to mediate their biological effects.[1][2][3][4] SHRs can produce slow genomic responses or rapid, non-genomic responses in the case of mSRs.[5]