Thehypothalamic–pituitary–prolactin axis (HPP axis), also known as thehypothalamic–pituitary–mammary axis orhypothalamic–pituitary–breast axis, is ahypothalamic–pituitary axis which includes thesecretion ofprolactin (PRL; luteotropin) from thelactotrophs of thepituitary gland into thecirculation and the subsequent action of prolactin ontissues such as, particularly, themammary glands orbreasts.[1][2] It is involved inlobuloalveolar maturation of the mammary glands duringpregnancy and the induction and maintenance oflactation followingparturition.[3]Hormones that control the secretion of prolactin from the pituitary gland includedopamine ("prolactin-inhibiting factor", or "PIF"),estradiol,progesterone,thyrotropin-releasing hormone (TRH), andvasoactive intestinal peptide (VIP).[1][4]
