Mammary gland gestation, serum progesterone remains at a stably high concentration so signaling through its receptor is continuously activated. As one of the transcribed genes, Wnts secreted from mammary epithelial cells act paracrinely to induce more neighboring cells' branching. When the lactiferous duct tree is almost ready, "leaves" alveoli are differentiated from luminal epithelial cells and added at the end of each branch. In late pregnancy and for the first few days after giving birth, colostrum is secreted. Milk secretion (lactation) begins a few days later due to reduction in circulating progesterone and the presence of another important hormone prolactin, which mediates
Witch's milk not recommended. In folklore, witch's milk was believed to be a source of nourishment for witches' familiar spirits. It was thought to be stolen from unwatched, sleeping infants. In other cultures expressing milk from the infant's breasts is supposed to contribute to a good breast shape in adulthood. Blood from the nipples is nearly always benign and frequently associated with duct ectasia; it should only be investigated when it is unilateral. Witch's milk Witch's milk or neonatal milk is milk secreted from the breasts of some newborn human infants of either sex. Neonatal milk secretion is considered a normal physiological