Vasopressin is an antidiuretic hormone that is secreted through the posterior pituitary after being formed in the hypothalamus. Despite its name the posterior pituitary is actually a large collection of axonal projections from the hypothalamus and is responsible for the secretion of the two hormones oxytocin and vasopressin. Both sexes produce this hormone but in the male body testosterone and vasopressin enhance each other greatly. This hormones main function is to regulate fluid volume by reducing the loss of water, but it also has an effect on our behavior as well. Because of the male’s higher level of testosterone, the synergy of vasopressin and testosterone can influence sexual and social behavior. In men I stimulates sexual arousal, partner recognition, and mate guarding.
Oxytocin is another antidiuretic hormone secreted through the posterior pituitary, but the difference is that it synergizes more efficiently with estrogen which is produced in higher amounts by females. Even though it is present in both sexes, the effects are much stronger in women. It facilitates childbirth and nursing for women. In both men and women, its production spikes during sex but for males it seems to drop dramatically right after, which is linked to the common behavior of men being very separate after sex.