Galactorrhea or galactorrhoea is the spontaneous flow of milk from the breast, unassociated with childbirth or nursing.
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.  Galactorrhea also occurs in males, newborn infants and adolescents of both sexes. 
Although frequently benign, it may be caused by serious underlying conditions and should be properly investigated.
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. 
Lactation requires the presence of estrogen, progesterone and prolactin, and the evaluation of galactorrhea includes eliciting a history for various medications or foods (methyldopa, opiates, antipsychotics, serotonin reuptake inhibitors, as well as licorice) and for behavioral causes (stress, and breast and chest wall stimulation), as well as evaluation for pregnancy, pituitary adenomas (with overproduction of prolactin or compression of the pituitary stalk), and hypothyroidism. Adenomas of the anterior pituitary are most often prolactinomas. Overproduction of prolactin leads to cessation of menstrual periods and infertility, which may be a diagnostic clue. Galactorrhea may also be caused by hormonal imbalances owing to birth control pills.
Galactorrhea is also a side effect associated with the use of the second-generation H2 receptor antagonist Cimetidine (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 
Main article: witch's milk
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.
See also 
- Galactagogue, a substance that promotes lactation in humans and other animals
- ^ a b Sakiyama, R.; Quan, M. (1983). "Galactorrhea and hyperprolactinemia". Obstetrical & gynecological survey 38 (12): 689–700. PMID 6361641.
- ^ Rohn, R. D. (1984). "Galactorrhea in the adolescent". Journal of adolescent health care : official publication of the Society for Adolescent Medicine 5 (1): 37–49. PMID 6420385.
- ^ Whitman-Elia, G. F.; Windham, N. Q. (2000). "Galactorrhea may be clue to serious problems. Patients deserve a thorough workup". Postgraduate Medicine 107 (7): 165–168, 171. PMID 10887453.
- ^ Potts, Malcolm (1999). Ever Since Adam and Eve: The Evolution of Human Sexuality. p. 145. ISBN 0-521-64404-6.
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