Amenorrhea is the absence of menstruation. Menstruation is a woman's monthly period.

Primary amenorrhea is when a girl has not yet started her monthly periods, and she:

• Has gone through other normal changes that occur during puberty
• Is older than 15

Primary amenorrhea; No periods - primary; Absent periods - primary; Absent menses - primary; Absence of periods - primary

Most girls begin menstruating between ages 9 and 18, with an average of around 12 years old. Primary amenorrhea typically occurs when a girl is older than 15, if she has gone through other normal changes that occur during puberty. Primary amenorrhea may occur with or without other signs of puberty.

Being born with poorly formed genital or pelvic organs can lead to primary amenorrhea. Some of these defects include:

• Blockages or narrowing of the cervix
• Imperforate hymen
• Missing uterus or vagina
• Vaginal septum

Hormones play a big role in a woman's menstrual cycle. Hormone problems can occur when:

• Changes occur to the parts of the brain where hormones that help manage the menstrual cycle are produced
• The ovaries are not working correctly

Either of these problems may be due to:

• Anorexia
• Chronic or long-term illnesses, such as cystic fibrosis or heart disease
• Genetic defects or disorders
• Infections that occur in the womb or after birth
• Other birth defects
• Poor nutrition
• Tumors

In many cases, the cause of primary amenorrhea is not known.

A female with amenorrhea will have no menstrual flow with or without other signs of puberty.

The doctor will perform a physical exam and ask questions about your medical history. A pregnancy test will be done.

Blood tests may include:

• Estradiol
• FSH
• LH
• Prolactin
• TSH
• T3 and T4

Other tests that may be done include:

• 17 hydroxyprogesterone
• Chromosome analysis
• Head CT scan 
• Head MRI scan
• Pelvic ultrasound
• Serum progresterone

Treatment depends on the cause of the missing period. Primary amenorrhea caused by birth defects may require medications (hormones), surgery, or both.

If the amenorrhea is caused by a tumor in the brain (pituitary tumor):

• Medications may shrink certain types of tumors.
• Surgery to remove the tumor may also be needed.
• Radiation therapy is usually only performed when other treatments have not worked.

If the condition is caused by a body-wide (systemic) disease, treatment of the disease may allow menstruation to begin.

If the amenorrhea is due to anorexia or too much exercise, periods will often begin when the weight returns to normal or the exercise level is decreased.

If the amenorrhea cannot be corrected, medicines can sometimes create a menstrual-like situation (pseudomenstruation). Medicines can help the woman feel more like her friends and family, and protect the bones from becoming too thin (osteoporosis).

The outlook depends on the cause of the amenorrhea and whether it can be corrected with treatment or lifestyle changes.

Periods are unlikely to start on their own if the amenorrhea was caused by one of the following conditions:

• Congenital defects of the upper genital system
• Craniopharyngioma
• Cystic fibrosis
• Genetic disorders

You may have emotional distress because you feel different from friends or family, or worry that you might not be able to have children.

Call your health care provider if your daughter is older than 15 and has not yet begun menstruating, or if she is 14 and shows no other signs of puberty.

Lobo RA. Primary and secondary amenorrhea and precocious puberty: etiology, diagnostic evaluation, management. In: Lentz GM, Lobo RA, Gershenson DM, Katz VL, , eds. Comprehensive Gynecology. 6th ed. Philadelphia, Pa: Mosby Elsevier; 2012:chap 38.

Styne DM, Grumbach MM. Puberty, ontogeny, neuroendocrinology, physiology, and disorders. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology, 12th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 25.

Bulun SE. The physiology and pathology of the female reproductive axis. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology, 12th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 17.