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
Giving What We Can Giving What We Can conducts research to determine which charities it recommends for members and other people to support. It differs from other charity evaluators in terms of the importance given to metrics of charity performance. While evaluators such as Charity Navigator use the fraction of donations spent on program expenses versus administrative overhead as an important indicator, Giving What We Can solely focuses on the cost-effectiveness of the charity's work. It believes that the variance in cost-effectiveness of charities arises largely due to the variance in the nature of the causes that the charities operate in, and therefore makes