– Tachykinin 3 (TAC3) is a secreted protein that belongs to the Tachykinin family. Tachykinins are active peptides that excite neurons and evoke behavioral responses; they are potent vasodilators and secretagogues, and contract many smooth muscles in pregnancy. TAC3 is primarily expressed in the central and peripheral nervous systems and functions as a neurotransmitter. It is also expressed in the outer syncytiotrophoblast of the placenta and may be associated with pregnancy-induced hypertension and pre-eclampsia. TAC3 acts as the ligand for the neurokinin-3 receptor, mutations in this gene are associated with normosmic hypogonadotropic hypogonadism.