High-purity oxytocin is a peptide hormone secreted by the posterior pituitary gland. Synthesized within the paraventricular and supraoptic nuclei of the hypothalamus, it consists of nine amino acids and is transported to the neurohypophysis for release at a rate of 2 to 3 millimeters per day. The cysteine (Cys) residues located at positions 1 and 6 form a cyclic hexapeptide structure via a disulfide bond.
Oxytocin functions to stimulate milk secretion by the mammary glands, promote the contraction of uterine smooth muscle during childbirth, and foster maternal bonding. Furthermore, it helps reduce the levels of stress hormones-such as adrenaline-within the body, thereby lowering blood pressure. It is not exclusive to women; both men and women are capable of secreting it.