Oxytocin is synthesized in the hypothalamus and involved in the control of lactation and parturition. Oxytocin is secreted within the brain and from a few other tissues, including the ovaries and testes. Oxytocin differs from antidiuretic hormone in two of the nine amino acids. Both hormones are packaged into granules and secreted along with carrier proteins called neurophysins. Human Oxytocin indirectly stimulates uterine smooth muscle contractions and stimulates the mammary glands to increase lactation without increasing the production of milk.