I have a issue with my thyroid and my dose has to be changed because part of it was removed due to cancer a few years back. So although its underactive my meds do not help too much. When I have my radiation scans I have to come off them completely for a bit before the scan hypo hell us thyroid cancer sufferers call it. Luckily my next scan is a fair bit away so I am on them but, its been hard getting my TSH level right.