Hyperprolactinemia: the presence of abnormally high prolactin in the blood. Normal blood prolactin levels are less than 20 – 25 ng/ml. Prolactin secretion is inhibited by dopamine which is also known as prolactin inhibitory factor. Hyperprolactinaemia can result from multiple causes including pregnancy, hypothyroidism (low thyroid), kidney failure, medications, distortion of the pituitary gland and stalk from a tumor (“stalk compression”) and from a prolactinoma. Learn more.