I have not had my thyroid removed. But I was taking levothyroxine for over 5 years before I had IDC. I took anastrozole for 12 months then switched to exemestane last November, neither drug effected my thyroid levels. I currently take 88 mcg daily for my thyroid. I have it tested yearly. Good luck and yes discuss it with both doctors. In 2016 I had trouble getting my dosage right, they had to increase it - but you have to take the new dose for 90 days before they know if it worked at that dosage. They changed my dosage 3 times that year. It was frustrating. Long before I had BC - so it may be completely unrelated.