Pregnancy is often the first thought when a period is missed, but there are many reasons for having a late period. Increased risk is associated with extreme and prolonged exercise (particularly without adequate conditioning), body fat content less than 15% to 17%, extreme obesity, and taking hormonal supplements.

Anxiety over a possible pregnancy may cause a missed period, thereby increasing the anxiety even further. Emotional distress from other causes can also cause a missed period.

Drugs such as busulfan, chlorambucil, cyclophosphamide, oral contraceptives, phenothiazines, and non-oral contraceptives (such as Norplant and Depo-Provera) can all cause scanty or missed periods. Also, procedures such as a dilation and curettage (D and C) can cause a woman to develop amenorrhea if scar tissue develops within the uterine cavity.

Early appearance of menopause may account for some cases (menopause is normal for women over age 45).

The incidence of secondary amenorrhea (due to some cause other than pregnancy) is about 4% in the general population.

• Previously had one or more menstrual periods
• No menstrual period for 6 months or longer

Note: Other symptoms associated with amenorrhea depend on the cause. They may include headache, galactorrhea (breasts produce milk in a woman who is not pregnant or breastfeeding an infant), marked weight gain or weight loss, dry vagina, increased hair growth in a "male" pattern (hirsutism), voice changes, and breast size changes. If amenorrhea is caused by a pituitary tumor, other symptoms related to the tumor, such as visual loss, may be present.

The physical examination will probably include a pelvic examination. Physical and pelvic examinations must rule out pregnancy before other diagnostic testing begins. The patient may be encouraged to discuss her fears and, if indicated, may be referred for psychological counseling.

Diagnostic tests that may be performed include:

• Endometrial biopsy
• Progestin withdrawal
• Prolactin level
• Serum hormone levels such as testosterone levels
• Thyroid function studies
• Pregnancy test (serum HCG)
• FSH (follicle stimulating hormone level)
• LH (luteinizing hormone level)
• TSH (thyroid stimulating hormone; other thyroid function tests)
• Karyotype to rule out the presence of Y chromosome abnormality
• CT scan of the head may be done if a pituitary tumor is suspected

Treatment depends on the cause of the amenorrhea. If it is caused by another systemic disorder, normal menstrual function usually returns after the primary disorder is treated.

For example, if the primary disorder is hypothyroidism, then amenorrhea will be cured when the thyroid disorder is treated with thyroid supplements.

If the primary cause is obesity, vigorous athletics, weight loss, or similar factors, treatment recommendations may include moderation in exercise and weight control.

The outcome depends on the cause. Most of the conditions that cause secondary amenorrhea will respond to treatment.

By itself, amenorrhea does not cause complications. However, the conditions that cause amenorrhea may have complications.

Call for an appointment with your primary health care provider or OB/GYN provider if you are a woman and have missed more than one period so that the cause, and appropriate treatment, can be determined.

Prevention depends on the cause. For example, moderate exercise instead of extreme exercise, weight control, and other measures may be helpful.