In order to produce milk, hormones are needed. The two main hormones are prolactin and oxytocin. The regulation of prolactin levels in the plasma is controlled by the dopaminergic system. Prolactin acts on the human breast to produce milk. It takes several minutes of the infant sucking at the breast to cause prolactin secretion.
Prolactin is also important in inhibiting ovulation.
Suckling at the breast stimulates the neurohypophysis to produce and release oxytocin in an intermittent manner. Oxytocin also causes uterine contractions. Fil acts locally within each breast. Fil is secreted into breast milk. When the breast is not emptied, Fil remains in contact with the alveolar cells.