After the mature, unfertilized egg is released from the ovarian follicle, the uterus prepares to shed its endometrium. There is a strong drop-off in estrogen and progesterone; because estrogen is a serotonin producer, this decline is linked to significant changes in one's daily life, including both mood (increased anxiety and depression) and physical symptoms (cramps, headaches, acne). The drop-off of these hormones signals the beginning of the menses, also known as the beginning of the shed of the uterine lining.