Prolactin is one of the many hormones secreted by the pituitary gland. Its function is to promote the secretion of milk, but if the amount of the hormone is too high, it will affect other endocrine secretions and cause infertility. Prolactin can make the ovaries unresponsive to gonadotropins, thus affecting the function of the ovaries. When prolactin is increased, symptoms of estrogen deficiency may occur, such as closed menstruation, non-ovulation, vaginal dryness and facial flushing. Possible causes of increased prolactin in blood include: 1. lactation; 2. hypothalamic and pituitary disorders; 3. hypothyroidism; 4. renal hypofunction; 5. malignant tumors in other areas (e.g. ovarian cancer, kidney cancer); 6. breast and chest wall disorders (e.g. chest wall trauma, lobular hyperplasia of the breast); 7. drug effects (e.g. taking lisinopril, oral contraceptives, methyldopa, etc.). If high prolactin is found, the cause should be promptly identified.