I am only a patient but in my experience, I have not found that the pituitary itself causes white matter damage. That being said, it can be caused by high blood pressure (pituitary can cause that) stroke (ditto), and low immunity conditions (some pituitary conditions reduce immunity, and once you have one auto-immune disease it is easier to get another).
Pituitary disorders do cause depression. Some of us get dizzy but I am not sure if related.
Your doctor has to find the type of pituitary tumor and the source of the white matter damage.