Diagnostic Blood Test: Prolactin Prolactin is a hormone produced by the pituitary gland. Changes in prolactin levels may be a sign of problems with the pituitary, thyroid, kidneys, or hypothalamus. Excessive levels of prolactin can impair hormone production.In men, elevated levels can cause a reduced sex drive, erectile dysfunction, impaired fertility, and a lack of energy. In women, prolactin helps the breasts develop and triggers the production of milk. Atypical prolactin levels can lead to a reduced sex drive, impaired fertility, changes in menstrual periods, or the production of milk unrelated to childbirth.Note: This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin. Cease biotin supplementation at least 72 hours prior to blood draw.