There are a couple of factors to consider in your case.
Being a hypothyroid person that itself causes puffy eyes,due to accumulation of protein and fluids below the skin. Once you are treated it will regress with time.
You are right that hyperthyroidism
causes most of the eye problems but more of eye protrusion,double vision
,inability to close the eye lids ....and so on rather than puffiness.
And you have mentioned a non functional Pituitary Adenoma.Since Pituitary gland
is very close to the orbit any tumour must not be ignored ,as there is a chance of extension towards the orbital structures and it's consequences.
Get a through ophthalmic examination (if possible an Orbit specialist) to record your optic nerve
and ocular muscle status for further follow up.
Since you have not mentioned your age your white spots
in MRI could be due to senile changes.
Hope this helps and wish you a faster recovery. Take care.