Pituitary gland tumors almost always occur in the anterior lobe. More than 10 percent of all tumors inside the skull develop in the pituitary gland. There are two main types.
Pituitary adenomas are overgrowths of one or more of the cell types in the gland.
These tumors are almost always benign. But because they grow in a confined space they may run out of room and may damage the nerves leading from the eyes, cause headaches, and eventually cause serious brain disorders if they begin to increase further in size. About 50 percent of all pituitary adenomas secrete abnormal amounts of the hormone prolactin. This may cause no symptoms. Or it may result in impotence, absence of menstrual periods, or Galactorrhea.