Amenorrhea is the absence of menstruation in a woman of reproductive age. Menstruation is part of the female reproductive cycle. During menstruation, commonly called a “period,” the lining of the uterus is shed when no fertilized egg has implanted in it. This typically happens on a monthly basis.
There are two types of amenorrhea, and several possible causes. Treatment varies depending on the cause, symptoms and age of the woman. Amenorrhea also occurs naturally during pregnancy and lactation.
The two types of amenorrhea are primary and secondary. Primary amenorrhea is when menstruation does not start. If a girl is 16 and has not had a period, or 14 with no indication of puberty having started, primary amenorrhea will be suspected. Causes may include a congenital absence of the uterus, problems with the ovaries and ovulation, or a delay in puberty.
Secondary amenorrhea happens when an established menstrual cycle stops. Since women’s cycles may be irregular, secondary amenorrhea is suspected after three months without a period in women with regular cycles, and after six months in women with a history of irregular periods. Some causes of secondary amenorrhea include some type of hormone disturbance, premature menopause, or intrauterine scars.
Another cause of amenorrhea may be intense exercise. While health professionals used to think that a lack of body fat, or an alteration in body chemistry due to exercise caused athletic amenorrhea, they now suspect that the cause is available energy. These women simply do not take in enough calories to support both their exercise and a menstrual cycle.
Amenorrhea is a natural occurrence during pregnancy. When a fertilized egg implants in the uterine lining, the lining is not shed. Lactation, or breastfeeding, also causes amenorrhea because it suppresses ovulation. This varies greatly, however, among individual women, and also with the frequency and level of breastfeeding. Because of this variation, it is unwise to rely on breastfeeding as a source of birth control.
Amenorrhea can also be induced by certain drugs. Amenorrhea is especially associated with certain types of hormonal contraceptives, such as Depo-provera, sometimes called “the shot,” and extended cycle combined hormonal birth control pills. It may take up to one year to resume menstruation after stopping some of these drugs.