A new class of steroid hormone receptors has recently been discovered and those are the cell membrane receptors (usually steroid hormone receptors are intracellular receptors, cytoplasmic or nuclear). Membrane steroid receptors are G protein-coupled receptors (GPR) and an example is GPR30 which binds estrogen. After estrogen binds to the receptor this pathway activates adenylyl cyclase which produces cAMP from ATP.