When I had a high TSH, I was told the pituitary gland was the cause and it was because the thyroid gland(s) were not producing enough of thyroid hormone. The pituitary gland stimulates the thyroid glands. I had two nodules, that were checked and benign. This was in 1988 and I have been on Synthroid ever since and have never had any negative anything. Armour thyroid is typically not covered by Medicare plans, fyi.