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
This Is What the Truth Feels Like originally issued as a promotional single before being released as the album's third single on May 23, 2016. After giving birth to her third son on February 28, 2014, Stefani made her first public appearance at the 2014 Coachella Valley Music and Arts Festival on April 12, 2014, performing "Hollaback Girl" at the request of her longtime collaborator and friend Pharrell Williams, who was one of the festival's headliners. After the performance, Williams hinted at a possible return for the singer. In September 2014, she revealed she was writing for two records: her third solo studio album and her band