The most important function of vasopressin is the reduction of free-water clearance by the kidney. At high concentrations, it contracts smooth muscle and initiates the conversion of glycogen to glucose in the liver. Secretion of vasopressin into the hypothalamopituitary circulation modulates the release of adrenocorticotrophic hormone (ACTH) from the anterior pituitary. Oxytocin aids contraction of the pregnant uterus and assists milk ejection during lactation. There is evidence that oxytocin may aid contraction of the seminal vesicles of the testis, may influence ovarian function, may have some effect in the anterior pituitary on the response of gonadotrophins to gonadotrophin-releasing hormone (GnRH) and may also increase lipolysis in the adipocyte.
