Galactorrhea is simply inappropriate lactation, and it is not representative of a specific disease but rather is a sign of an underlying condition. It is caused by increased levels of prolactin; prolactin levels are controlled by the hypothalamus through positive and negative feedback of the pituitary gland. Galactorrhea can result from stimulation of the nipple, medications, sexual intercourse, stress, hypothyroidism, or a prolactin-secreting pituitary adenoma (prolactinoma). Very rarely, those who do not produce milk (agalactia) may have an abnormality of prolactin receptor. Lactation is considered physiologic in pregnant individuals after the first trimester as well as up to 2 years after cessation of breastfeeding.

Galactorrhea is relatively common in women: as many as 20%-25% of all women are affected at some point in their lives. Men can rarely have galactorrhea, most often from medications.

Galactorrhea may occur unilaterally or bilaterally. The discharge can have different colors (white, yellow, or green). Typically, blood is not present.  

Risk factors for galactorrhea include the use of medication from certain classes (most commonly antipsychotics with antidopaminergic properties), as well as other medical conditions, such as hypothyroidism, hypothalamic-pituitary disorders, and chest wall irritation.

Pediatric Patient Considerations:
Galactorrhea can be physiologic in the first month of life.