You have mentioned the reason for your drooping of the upper lids in your question itself. A bulky pituitary gland
can give mechanical pressure over the third cranial nerve
causing damage to the nerve fibres responsible for the upper lid movement. It can also affect your field of vision in the same eye or both the eyes.
First get yourself evaluated by a neuro ophthalmologist to know how much ptosis
and field of vision you have in both your eyes, and take a neurosurgeon opinion of why the pituitary is bulky and the invention needed.
Once the 3rd cranial nerve is free of pressure, then your ptosis can( the recovery varies between individuals) improve. There are surgical procedures available for ptosis correction ,if there is persistent residual,significant drooping even after you are free from the pituitary problem.
So let's hope for the best and find out the reason for your bulky pituitary. Keep us updated about your health and get well soon.