I just had a BT, then when it should my thyroid was underactive I had an ultrasound of my neck to see if there was any underlying cause. It turned out there was no abnormality for me, it was underactive just because LOL! Now I'm on Oroxine tablets every day for the rest of my life. Apparently there are regular BTs as well to make sure the meds are working, but I haven't had one yet as I only found out about 2 months ago.