The next step test (this is my term calling it the "next step" I'm not sure if it actually is) is Thyroid Peroxidase (TPO). Basically the body does not think the thyroid belongs there and starts to attack it. This is what they believe is happening (it's still fairly recent). I don't remember all the specifics about it since it's new to me, but it I think causes your thyroid to be under-active if I understand it all correctly. Please don't quote me. I am not in the medical field.

Bottom line, if you truly believe something is wrong with you be persistent. It took me over a year to find this out. Good luck to you!