What Causes Low TSH And Iron Levels?

Hello, I am a 26 year old female. 2 years ago I lost a small patch of hair on both sides of my head. Both underneath so not visible. I was told I had alopecia and a thyroid problem. My thyroid was low, and TSH level even lower, extemely low iron (6), and low vitamin d. They also found multipile nodules on my neck/thyroid on the right side, and a few on the left. They were checked, fluid filled and solid, and all were benign. After being on thyroid medication, iron, vit c and d for quite awhile I had my blood drawn again. Iron was not increasing much. The thyroid meds I quit taking because the Dr told me it wasn't helping shrink my nodules and my thyroid level was back up. A few months ago I got blood drawn again. I needed iron iv treatments for a month and that is now ok. Vitamin D level was ok for now. But thryoid level was back down and tsh even lower. I was put back on the thyroid meds and it's slowly helping. Then my Dr ordered an MRI in case I had a pituitary problem because of the low tsh. My pituitary was normal but they found a 2 cm around brain tumor! I was told it is in the middle, right lateral ventricle, and for now is not causing damage. They still cannot figure out why I have the thyroid problem or the iron problem. Can you think of anything?