Lactation in Humans

Abstract

For successful lactation it is essential that the patient be endowed with breast tissue that is capable of normal response to estrogens, progesterone, and lactogenic hormones (Fig. 58). The rising titer of the steroid hormones during pregnancy causes maximum development of the lobulo-alveolar system and presumably sensitizes the glandular tissue for the action of lactogenic hormones. Prolactin is secreted in increased amounts during pregnancy, but its release from the pituitary and the placenta is inhibited by the high estrogen titer. It should be pointed out that the colostrum, that may exude or be expressed from the breasts during pregnancy, contains little, if any, milk and consists chiefly of desquamated epithelium and transudate. It is not until about the third day post-partum, when the estrogens have been nearly completely cleared, that the breasts become engorged by the active secretion of milk. It is presumed that this is caused by the release of LTH and STH following the removal of the estrogen “brake.” For lactation to continue actively, it is necessary that there should be regular suckling or artificial pumping of the breasts. This suggests the importance of the neural pathway from the breasts to the hypothalamus mediating the continued secretion of oxytocin and lactogenic hormones.