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
  • Some medications, such as:
    • Stopping or starting to take birth control pills or other hormones
    • Certain blood pressure drugs
    • Certain psychiatric medications
    • Anti-nausea drugs
    • Some antigastroesophageal reflux medications
    • Some pain killers
  • Certain herbs, such as :
  • Illicit drugs, such as marijuana and opioids
  • Sexual stimulation of the breast
  • Certain diseases, such as underactive or overactive thyroid, and chronic kidney failure, or liver disease
  • Chronic emotional stress
  • Hypothalamic tumors or disease
  • Chest wall conditions, such as:
    • Shingles
    • Trauma
    • Burns
    • Surgical scars
    • Tumors of chest wall
  • In newborns, high levels of circulating estrogen may result in enlarged breast tissue and secretion of milk