Prolactin (PRL) is a hormone produced by a small organ at the base of the brain called the anterior pituitary gland. Prolactin (PRL) is a hormone produced by a small organ at the base of the brain called the anterior pituitary gland. It is best known for producing breast milk in women. Prolactin is usually found in low levels in both men and women. It will rise significantly during pregnancy and breastfeeding and returns to normal very quickly after breastfeeding stops.