Does a total thyroidectomy show up in a PET scan as a normal functioning gland?

Dear Ask The Doctor: I have RA, with lung nodules, and it was recommended back in May to have a PET scan, which confirmed RA lung. I am moving, and just requested the records from the pulmonary doctor. I just read the PET scan for the first time and in the findings it states: "The thyroid gland demonstrates normal physiologic activity". As I have Hashimoto's and had to have a total thyroidectomy in 2002, plus my endo did an ultrasound in 2008 to confirm it had not grown back, how is it possible for my thyroid gland to be active? I sent a fax to the PET scan radiologist, my primary, and the pulmonary doctor asking for an explanation and no one has replied. Could my thyroid replacement medication trick a PET scan to show I still have a thyroid gland? I am really confused, thanks for this service.

Dear Cathy:

I realize how you feel after reading your PET scan results showing normal thyroid activity. Let me reassure you that not all the “Total Thyroidectomies “always remove 100 % of the thyroid tissue. In fact, in the practice we find that 30 % of these procedures had significant thyroid tissue left. If this is the case, then a PET scan might have probably detected this remnant tissue with more accuracy than an ultrasound.

On the other hand, the medication that you are taking to replace your thyroid hormones certainly can’t alter the results of your PET scan and show a normal thyroid activity. I would suggest you to have a re evaluation with your endocrinologist to rule out the presence of thyroid tissue and to follow up your hormone levels. I wish you the best.