Is tripping over furniture in my house a common sign of pituitary cancer?

Not commonly: This is not a common sign of pituitary tumor unless the reason why you trip over the furnitures is because you don't have peripheral (sideview) vision, which is a sign of a large pituitary tumor. Pituitary tumor usually does not cause balance issues.

No it is not: There are many causes of tripping. The furniture if obstructing your way of passage can definitely result in your tripping. But if you feel that you just fall without any obstructing object, or if you feel like you have problems with your gait, or have unsteady gait or loose your balance when ambulating, or your legs give out, then go see your doctor, mass compressing spinal cord may be a cause..