The
luteal phase is the latter phase of the
menstrual cycle (in humans and a few other animals) or the earlier phase of the
estrous cycle (in other
placental mammals). It begins with the formation of the
corpus luteum and ends in either pregnancy or
luteolysis. The main hormone associated with this stage is
progesterone, which is significantly higher during the luteal phase than other phases of the cycle. The opposite of the luteal phase, the rest of the two weeks, is called the
follicular phase.