Galactorrhea is a discharge of milk-like substance from the breast that is not associated with breastfeeding after pregnancy. This condition mainly occurs in women. It does occur in men, but much less commonly. The milky white discharge can come from one or both breasts, and the breast may leak fluid with or without stimulation.

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Galactorrhea has many causes, though sometimes the cause is unknown. Tumors of the pituitary gland, called pituitary adenomas or prolactinomas, can cause galactorrhea. The pituitary is a small gland attached to the brain. Pituitary tumors are usually not cancerous. They can cause galactorrhea when they produce excess prolactin, a hormone that stimulates milk production.

Other causes of galactorrhea include:

  • Hormonal imbalance, such as hypothyroidism
  • Some medicines, such as:
    • Stopping or starting to take birth control pills or other hormones
    • Blood pressure drugs
    • Tricyclic antidepressants
    • Tranquilizers
    • Antinausea drugs
    • Some antigastroesophageal reflux medicines
    • Some pain killers
  • Certain herbs, including:
  • Illicit drugs, such as:
    • Marijuana
    • Opiates
  • Sexual stimulation of the breast
  • Certain diseases, including:
  • Chronic emotional stress
  • Hypothalamic tumors or disease (such as tuberculosis)
  • Chest wall conditions, such as:
    • Shingles
    • Trauma
    • Burns
    • Surgical scars
    • Tumors of chest wall
  • In newborns, high levels of circulating hormones (estrogen) may result in enlarged breast tissue and secretion of milk.