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prolactin pro·lac·tin (prō-lāk'tĭn)
Abbr. PRL A pituitary hormone that stimulates and maintains the secretion of milk. Also called lactogenic hormone, lactotropin, luteotropic hormone, luteotropin.
a protein hormone produced by the pituitary gland of mammals that acts with other hormones to initiate secretion of milk by the mammary glands. It also acts to maintain the corpus luteum of the ovary, which is the source of the female sex hormone progesterone. Its function in males is not known. In humans prolactin is similar to human growth hormone.