Premenstrual syndrome or PMS describes a change in mood and body functions just prior to menstruation, often causing bloating and pain due to the retention of fluids and mood swings due to high levels of the hormones estrogen and progesterone that are released during ovulation. Most women feel bodily changes during menstruation, but for many women the symptoms are at their worst before menstruation and are actually relieved when the menstrual cycle begins. Symptoms vary widely in severity and women can go through violent mood swings during this time.