Pituitary tumor. It really depends on the type of tumor, its surgical removal or treatment by therapy. Some of these tumors are benign and with treatment can lead to a normal lifespan - it is all based on the tumor type and the available treatment.
No. The answer depends on the size of the tumor (> or < 1cm) and whether or not it is producing any hormones. The most common type of pituitary tumor is a non-functioning tumor. This type, if small and not affecting the optic chiasm, does not cause any problems and does not "shorten your lifespan.".