The G<sub>q</sub>-coupled membrane estrogen receptor (G<sub>q</sub>-mER) is a G protein-coupled receptor present in the hypothalamus that has not yet been cloned. It is a membrane-associated receptor that is G<sub>q</sub>-coupled to a phospholipase CâÂÂprotein kinase CâÂÂprotein kinase A (PLCâÂÂPKCâÂÂPKA) pathway. The receptor has been implicated in the control of energy homeostasis. G<sub>q</sub>-mER is bound and activated by estradiol, and is a putative membrane estrogen receptor (mER). A nonsteroidal diphenylacrylamide derivative, STX, which is structurally related to 4-hydroxytamoxifen (afimoxifene), is an agonist of the receptor with greater potency than estradiol (20-fold higher affinity) that has been discovered. Fulvestrant (ICI-182,780) has been identified as an antagonist of G<sub>q</sub>-mER, but is not selective.