Galactorrhea is reported to occur in 5%-32% percent of women. Much of the difference in reported incidence can be attributed to different definitions of galactorrhea. Although frequently benign, it may be caused by serious underlying conditions and should be properly investigated. Galactorrhea also occurs in males, newborn infants and adolescents of both sexes.
It can be due to dysregulation of certain hormones or local causes such as excessive nipple stimulation. Hormonal causes most frequently associated with galactorrhea are hyperprolactinemia and thyroid conditions with elevated levels of TSH or TRH hormones. No obvious cause is found in about 50% of cases.
Galactorrhea is also a side effect associated with the use of the second-generation H2 receptor antagonistCimetidine (trade name: Tagamet). Galactorrhea can also be caused by anti-psychotics that cause hyperprolactinemia by blocking dopamine receptors responsible for control of prolactin release. Of these, risperidone is the most notorious for causing this complication. Case reports suggest proton-pump inhibitors have been shown to cause Galactorrhea.
Neonatal milk or witch's milk is milk secreted from the breasts of many newborn infants. It is considered a normal variation and no treatment or testing is necessary. In folklore, witch's milk was believed to be a source of nourishment for witches' familiar spirits.