Pituitary tumors are classified as functional or non-functional. Functional refers to pituitary tumors that secrete too many hormones, such as lactogenic adenomas that cause amenorrhea, lactation, and infertility; growth hormone adenomas that cause enlarged hands and feet or gigantism; adrenocorticotropic hormone adenomas that cause hypertension and centripetal obesity; and thyrotropin adenomas that cause hyperthyroidism. Non-functional means that the pituitary tumor cells do not secrete hormones, and these tumors usually grow larger and cause visual impairment before they are detected. Different pituitary tumors have different manifestations, and some patients first see obstetrics and gynecology, ophthalmology, or endocrinology before the symptoms of pituitary tumors are discovered.