A menstrual disorder is characterized as any abnormal condition with regards to a person's menstrual cycle. There are many different types of menstrual disorders that vary with signs and symptoms, including pain during menstruation, heavy bleeding, or absence of menstruation. Normal variations can occur in menstrual patterns but generally menstrual disorders can also include periods that come sooner than 21 days apart, more than 3 months apart, or last more than 10 days in duration. Variations of the menstrual cycle are mainly caused by the immaturity of the hypothalamic-pituitary-ovarian (HPO) axis, and early detection and management is required in order to minimize the possibility of complications regarding future reproductive ability. Though menstrual disorders were once considered more of a nuisance problem, they are now widely recognized as having a serious impact on society in the form of days lost from work brought about by the pain and suffering experienced by women. These disorders can arise from physiologic sources (pregnancy etc.), pathologic sources (stress, excessive exercise, weight loss, endocrine or structural abnormalities etc.), or iatrogenic sources (secondary to contraceptive use etc.). Types of menstrual disorders Premenstrual Disorders Premenstrual syndrome (PMS) or premenstrual tension refers to the emotional and physical symptoms that routinely occur in the two weeks leading up to menstruation. Symptoms are usually mild, but 5-8% of women experience moderate to severe symptoms that significantly affect daily activities. Symptoms may include anxiety, irritability, mood swings, depression, headache, food cravings, increased appetite, and bloating. Premenstrual dysphoric disorder (PMDD) is a severe mood disorder that affects cognitive and physical functions in the week leading up to menstruation. Premenstrual dysphoric disorder is diagnosed with at least one affective, or mood, symptom and at least five physical, mood, and/or behavioral symptoms. Disorders of cycle length Normal menstrual cycle length is 22–45 days. Amenorrhea is the absence of a menstrual period in a woman of reproductive age. Physiologic states of amenorrhoea are seen during pregnancy and lactation (breastfeeding). Outside of the reproductive years there is absence of menses during childhood and after menopause. Irregular menstruation is where there is variation in menstrual cycle length of more than approximately 8 days for a woman. The term metrorrhagia is often used for irregular menstruation that occurs between the expected menstrual periods. Oligomenorrhea is the medical term for infrequent, often light menstrual periods (intervals exceeding 35 days). Polymenorrhea is the medical term for cycles with intervals of 21