Common causes of increased prolactin include hypothalamic lesions, pituitary prolactinomas, primary hypothyroidism, hypoadrenalism, liver and kidney disease, medication factors, and other disease factors. Hypothalamic lesions such as craniopharyngiomas, ectopic pineal tumors with metastatic tumors may cause high prolactin levels. Pituitary prolactinoma increases blood prolactin concentration due to increased autonomous secretion of prolactin by prolactin cells. Pituitary growth hormone tumors and others increase the release of prolactin. Primary hypothyroidism, hypoadrenalism, and other disorders that weaken the feedback effect on the hypothalamus also increase prolactin secretion. Reduced metabolic clearance of prolactin by hepatic and renal disorders also increases blood prolactin concentrations. Drugs also have a certain effect on the results of prolactin measurement, such as oral contraceptives, cimetidine, etc. may lead to increased prolactin concentration. Polycystic ovary syndrome, primary hypogonadism, and gynecomastia also have increased prolactin. Recently, it has been found that fasting prolactin can be as high as two to three times normal in diabetic patients. Patients found to have high prolactin are advised to seek prompt medical attention.