From the Manufacturer:
Chaste Tree Berries (Vitex Angus-Cactus) stimulates the pituitary gland to produce more leutenizing hormone, this leads to greater production of progesterone during the second half (leuteal phase) of a woman's cycle. Vitex may help with premenstrual syndrome, amenorrhea, infertility, heavy or frequently occurring menses an hot flashes associated with peri-menopause.