I believe the thyroid is IS because of the tumor. I had a brain tumor near the pituitary and it effected it. It caused me to have secondary hypothyroidism and diabetes insipidus. They put me on synthyroid for the hypothyroidism, but only to treat hypothyroidism. They removed my tumors, because they were big enough. They may not be removing yours maybe because it's too small. I'm not sure. Again, the reason I have diabetes insipidus and secondary hypothyroidism, is because of my past tumors which effected my pituitary gland. Also, on my report it states I too have an "infundibulum remains deviated."
Crbn - why are you doing gamma before conventional surgery? Keep in mind that gamma will take time to work as well that there may be damage to the rest of the pituitary (which also happens with conventional, but with a good surgeon, is usually minimal).
I was diagnosed 12 years ago and had it surg removed and it has now returned you need to find out if it is a secreting tumor mine is prolcatin secreting and mine is not shrinking with meds, we are looking into a gamma knife, radiation that is pinpoint to your tumor find out more and let us know
good luck
Is your endo a regular endo or a neuro-endocrinologist?
I ask as you are not saying what kind of tumor it is - and that comes with testing, testing and more testing. An MRI can tell you some stuff, but very little. You need lab work.
As for the thyroid, the only way to know if it is pituitary related is how it is tested. If your doc only runs a couple of tests, well, he is not going to know - you need to run a lot of tests and the anti-bodies too.
The MRI report is just that the left side is larger than the right which often means there is a tumor there and a deviation of the stalk to the left - so that can interfere with any and all of your hormones.
Pit tumors are only removed if they cannot be treated with meds so it depends on the type. You only know the type by testing. I would find the doc who will test and get you balanced and so you will know what is going on. Get copies of everything!