Prolactin (PRL) is a hormone secreted by the pituitary gland. Elevated prolactin is called hyperprolactinemia and can cause problems such as bilateral breast overflow, menstrual disorders, infertility, and headaches. The most common cause is pituitary disorders, such as pituitary tumors, but also hypothalamus, thyroid, polycystic ovary syndrome, and medications can cause elevated prolactin levels. Because the measurement of prolactin levels is affected by nipple stimulation, stress, and exercise, if the prolactin level is slightly elevated in a single measurement, it is usually better to repeat the test once and still elevated before considering the diagnosis of hyperprolactinemia. Ideal testing method: Avoid sexual intercourse, breast stimulation, exercise and stress before blood sampling, and have blood drawn for testing from 9-11 a.m. A quiet rest period of one hour is recommended before blood is drawn. After the diagnosis of hyperprolactinemia is confirmed, the cause of the disease must be further clarified and the treatment targeted. First of all, medication can be considered. If the treatment is ineffective or if the pituitary tumor produces compression symptoms, surgery or radiation therapy can be considered.