Are pituitary tumors deadly?

No: But because of proximity to optic nerve can have adverse effect on vision if untreated.

Yes: You can bleed into the tumor, producing an agonizing death. A HGH producing tumor giving you acromegaly will take an average of 18 years off your life. An acth producing tumor giving you cushingism will eventually kill you. Even an aggressive prolactinoma, which usually just makes women stop cycling and lactate, and makes men impotent, can crush the bottom of the brain, causing death.

Usually not: Pituitary tumors are almost always benign, and most are amenable to surgical excision. Residual tumor is often treated with radiation therapy. Growth of some tumors may be stopped with oral medication. Regardless, some tumors tend to grow, albeit very slowly in general. Revision surgery is sometimes required, and one key to treatment is good surveillance for further growth with periodic mris.