The size of pituitary tumors varies greatly. Smaller pituitary tumors less than 1 cm or 10 mm in diameter are called pituitary microadenomas; pituitary tumors over 1 cm or 10 mm in diameter are called pituitary macroadenomas; some pituitary tumors are very large in diameter, even up to 4 cm or more, and are called pituitary macroadenomas. Microadenomas are more likely to occur in women and macroadenomas are more common in men. Giant adenomas are not particularly common clinically. The distinction between the size of pituitary tumor diameters is, on the one hand, to help evaluate the level of relevant pituitary hormones in the blood to help make a correct diagnosis of the condition and, on the other hand, to provide a basis for the choice of surgical procedure.