Discharge from the nipples is caused by many different conditions.

The breasts are glands that secrete milk in response to the hormone changes of pregnancy and especially to an increase in the hormone prolactin. Nipple discharge that is caused by milk produced during or just after pregnancy is called lactation. If it happens at other times, it is called galactorrhea.

Galactorrhea is often caused by an abnormal increase in prolactin. Prolactin is produced in the pituitary gland in the brain and secreted into the blood stream. Prolactin levels may rise due to a pituitary tumor, low thyroid function, kidney failure and the use of certain medications.

These medications increase the level of prolactin:

• Certain blood pressure drugs (verapamil, methyldopa)
• Anti-nausea drugs (metoclopramide)
• Antacids (cimetidine)
• Antidepressants (desipramine)

Make an appointment to see your doctor. He or she will likely order a blood test to check your prolactin level.

If the nipple discharge is not milk, then it is more worrisome. It may be caused by an infection or a tumor. That’s especially true if it is bloody or only comes from one nipple.

To determine the cause, your order will order lab tests on the fluid and a breast ultrasound. Sometimes special X-ray tests and a breast biopsy will also be necessary. Once the cause of the discharge is found, your doctor will prescribe the appropriate treatment.