Oxytocin is a small peptide comprising only nine amino acids, naturally produced in the hypothalamus and secreted by the posterior pituitary gland cells. It has also been isolated from placenta, ovaries, testes, adrenal glands, thymus, retina, and pancreas tissues. The active hormone is obtained by proteolytic cleavage of a larger precursor protein. It is no longer considered merely a neurohypophyseal hormone as its actions are considered to be far-reaching and include interaction with additional peptides. Oxytocin appears to be a protein with two independent natural functions. First, it appears to act as a neuropeptide produced by the hypothalamus to regulate bonding, reproduction, and birth. Oxytocin appears to be bloodborne and secreted by the placenta of pregnant animals to influence birth, milk production, and bonding with their young. Small amounts of the protein produced from testes may promote mating behavior and pair bonding.