Membrane androgen receptors (mARs) are a group of G protein-coupled receptors (GPCRs), which bind and are activated by testosterone and/or other androgens. Unlike the androgen receptor (AR), a nuclear receptor which mediates its effects via genomic mechanisms, mARs are cell surface receptors which rapidly alter cell signaling via modulation of intracellular signaling cascades. Known or proposed mARs include ZIP9 and GPRC6A.