This document discusses disorders of menstruation, including amenorrhea and premenstrual syndrome (PMS). It defines amenorrhea as the absence of menstrual periods, and describes primary amenorrhea as never starting periods and secondary amenorrhea as periods ceasing. Common causes include pregnancy, breastfeeding, medications, hormonal imbalances, eating disorders, and structural issues. PMS refers to physical and emotional symptoms in the one to two weeks before a period, with treatments including antidepressants, NSAIDs, diuretics, and dietary and lifestyle modifications.