Complex interactions among hormones control the start of menstruation during puberty, the rhythms and duration of menstrual cycles during the reproductive years, and the end of menstruation at menopause (which is usually defined as beginning 12 months after a woman's last period). The interactions occur in the following sequence:

• Hormonal control of menstruation begins in the hypothalamus (the part of the brain that coordinates and controls hormonal activity).
• The hypothalamus releases gonadotropin-releasing hormone in pulses.
• Gonadotropin-releasing hormone stimulates the pituitary gland to produce two hormones called gonadotropins: luteinizing hormone and follicle-stimulating hormone.
• Luteinizing hormone and follicle-stimulating hormone stimulate the ovaries.
• The ovaries produce the female hormones estrogen and progesterone, which ultimately control menstruation (see Biology of the Female Reproductive System: Menstrual Cycle).

Hormones produced by other glands, such as the adrenal glands and the thyroid gland, can affect the functioning of the ovaries and menstruation.

During the reproductive years, vaginal bleeding may be abnormal when menstrual periods are too heavy or too light, last too long, occur too often, or are irregular. Any vaginal bleeding that occurs before puberty or after menopause is considered abnormal until proven otherwise. Most causes of abnormal vaginal bleeding are not serious.

Menstrual disorders include premenstrual syndrome (PMS), menstrual cramps (dysmenorrhea), dysfunctional uterine bleeding, absence of menstrual periods (amenorrhea), and premature menopause. Some disorders that are related to the reproductive organs but not specifically to the menstrual cycle, such as pelvic congestion syndrome and polycystic ovary syndrome, cause some of the same symptoms as menstrual disorders.

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Deciphering Medical Terms for Menstrual Disorders* Term Description Amenorrhea No periods Dysmenorrhea Menstrual cramps or painful periods Hypomenorrhea Unusually light periods Menometrorrhagia Heavy bleeding during menstrual periods and bleeding that occurs frequently and irregularly between periods Menorrhagia (hypermenorrhea) Unusually long and/or heavy periods Metrorrhagia Bleeding that occurs frequently and irregularly between periods Oligomenorrhea Unusually infrequent periods Polymenorrhea Unusually frequent periods Postmenopausal bleeding Bleeding that occurs after menopause Premenstrual dysphoric disorder Severe psychologic symptoms that occur before the start of a period, end when or shortly after the period starts, and interfere with daily activities and/or relationships Premenstrual syndrome (PMS) Physical and psychologic symptoms that occur before the start of a period Primary amenorrhea No periods ever starting (at puberty) Secondary amenorrhea Periods that have stopped *Breaking the words into their components helps decipher them: a = no; dys = painful (or abnormal); hypo =deficient (or below normal); men = month; metro = uterus; oligo = few or scanty; poly = many or much; post = after; pre =before; rhagia = to burst forth; rhea = flow. Deciphering Medical Terms for Menstrual Disorders* Term Description Amenorrhea No periods Dysmenorrhea Menstrual cramps or painful periods Hypomenorrhea Unusually light periods Menometrorrhagia Heavy bleeding during menstrual periods and bleeding that occurs frequently and irregularly between periods Menorrhagia (hypermenorrhea) Unusually long and/or heavy periods Metrorrhagia Bleeding that occurs frequently and irregularly between periods Oligomenorrhea Unusually infrequent periods Polymenorrhea Unusually frequent periods Postmenopausal bleeding Bleeding that occurs after menopause Premenstrual dysphoric disorder Severe psychologic symptoms that occur before the start of a period, end when or shortly after the period starts, and interfere with daily activities and/or relationships Premenstrual syndrome (PMS) Physical and psychologic symptoms that occur before the start of a period Primary amenorrhea No periods ever starting (at puberty) Secondary amenorrhea Periods that have stopped *Breaking the words into their components helps decipher them: a = no; dys = painful (or abnormal); hypo =deficient (or below normal); men = month; metro = uterus; oligo = few or scanty; poly = many or much; post = after; pre =before; rhagia = to burst forth; rhea = flow.

Last full review/revision August 2012 by JoAnn V. Pinkerton, MD