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Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Amenorrhea

What Is It?

Amenorrhea means that a woman of childbearing age fails to menstruate.

A woman normally menstruates every 23 to 35 days. The cycle is regulated by the portion of the brain called the hypothalamus, which also controls body temperature, appetite and blood pressure. The hypothalamus stimulates the pituitary gland (located near the base of the brain) to release two hormones that regulate the female reproductive cycle: luteinizing hormone and follicle-stimulating hormone. These hormones influence the production of the hormones estrogen and progesterone, which are responsible for cyclic changes in the lining of the uterus, including menstruation. In order for a woman to have regular menstrual cycles, her hypothalamus, pituitary gland, ovaries and uterus must be functioning properly. Her cervix and vagina must also have a normal anatomy for menstrual blood to pass through.

There are two types of amenorrhea:

Primary amenorrhea occurs when a woman has not had her first menstrual period (menarche) by age 16. This condition, also called "delayed menarche," is most often due to late puberty, which is fairly common in teenage girls who are very thin or very athletic. These young women are typically underweight, and their bodies have not experienced the normal puberty-related rise in body fat that triggers the beginning of menstruation. In other girls, the delay of menstruation may be due to Turner's syndrome, a genetic disorder involving the sex chromosomes, or to abnormal female reproductive organs.

Secondary amenorrhea happens when a woman who has menstruated previously fails to menstruate for more than three months. Secondary amenorrhea can be caused by:

• Pregnancy (the most common cause)

• Breast feeding (lactation)

• Menopause, the normal age-related end of menstruation

• Premature ovarian failure (menopause before age 40)

• Hysterectomy (surgical removal of the uterus)

• Birth control pills

• Use of a long-acting progesterone, such as Depo-Provera, for birth control

• Tumors of the pituitary gland, especially prolactinomas

• Polycystic ovary syndrome, a condition in which there is excessive androgen (male hormone production) and other hormonal irregularities

• Endocrine disorders such as Cushing's syndrome, in which there are very high levels of cortisol, an adrenal hormone, or hyperthyroidism, abnormally high levels of thyroid hormone

• Emotional or physical stress

• Rapid weight loss

• Obesity

• Frequent strenuous exercise

• Chronic (long-term) illness, such as colitis, kidney failure or cystic fibrosis

• Chemotherapy for cancer

• Cysts or tumors in the ovaries

Amenorrhea affects 2% to 5% of all women of childbearing age in the United States. Female athletes, especially young women, may be more likely to have amenorrhea. While exercise or physical activity itself does not cause amenorrhea, it is more likely to occur in women who exercise very intensely or who increase the intensity of exercise rapidly. Women who engage in sports associated with lower body weight, such as ballet dancing or gymnastics, are more likely to develop amenorrhea than women in other sports.

From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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