Radioactive iodine uptake test if TSH suppressed

With a suppressed TSH (reason not confirmed), can iodine uptake test be in the normal range? I got 0.1% normal (.5%-4%)

I know the test result will exclude hyperthyroid. But .. will it confirm hypothyroid?

Since TSH is low (0.01), I think the test result will be below normal range unless someone has graves disease. Am I right?

Last edited by

10 Replies

  • Ali1101, the radioactive iodine uptake test is to check for hyperthyroidism. Low uptake may mean thyroiditis (inflammation) causing hyperthyroid levels and high uptake may indicate autoimmune Graves Disease as a cause of hyperthyroidism. It won't diagnose hypothyroidism.

    TSH 0.01 is low. What were your FT4 and FT3 levels?

  • Hi Clutter, FT4 (1.43 N 0.8-1.75) and FT3 (3.31 N 2.3-4.2). one doctor insisted on hyperthyroidism and another doctor excluded it. He thinks I have a secondary hypothyroidism (due to pituitary) also because I have hypo symptoms such as low heart rate, low O2 saturation, constipation ...

  • Ali1101, absolutely not hyperthyroid, FT4 and FT3 would be over range if you were hyperthyroid.

    FT4 is in the top quadrant of range and FT3 just over half way through range which are good levels and don't indicate hypothyroidism, primary or secondary. Symptoms sound very much like hypothyroidism. A trial of Levothyroxine could be tried. If symptoms improve it will show that you are hypothyroid despite the blood levels.

    It would be good to have a pituitary function test to rule out pituitary dysfunction and isolated TSH deficiency.

  • I agree with you and right now I'm in this trial but in my fifth week on 50 mcg levothyroxine, I felt abnormal temperature in my hands and legs although when I measured it orally was normal! may be it is just a spike like you said in the other post, I will do blood work soon to see how things look after the medications. I will ask if they do pituitary function test, but if pituitary is ruled out, what are the other possibilities ?

    By the way, I do appreciate your help so much your contribution is invaluable. Thank you so much Clutter.

  • Ali, your body has a lot of adjusting to do when it's been low on hormone and is suddenly replaced. Bits of your body start waking up when metabolism improves and it can be disconcerting for a while but should settle down in a few months.

    If pituitary dysfunction is ruled out there probably won't be further investigation. Hypothalmic dysfunction (tertiary hypothyroidism) is a possibility, but rare. The hormone replacement will address low hormone whatever the cause.

    Take your Levothyroxine dose after your blood test. If you are hoping for a dose increase have a fasting test (water only) and make it as early as possible when TSH is highest.

  • Thanks for posting this Clutter. So good to have this information 30 odd years after I had the RAIU! How trusting of doctors I was then!

  • J_bee, weren't we all! I still am trusting. I question more because I'm better informed now, older, more confident and want to weigh up pros and cons before agreeing to treatment. My endo was wrong about Levothyroxine not causing me problems, but it hasn't misplaced my trust, it's made me trust my instincts more.

  • Luckily I now have an Endo who I can question and he gives me pretty true answers about what NHS can and can't do (mostly can't). Think next time I see him might be the last if all bloods are 'within range'. But, then again, he might just have to go on monitoring me as I have since gone onto T4/T3 combo! Have just felt a bit better over the past couple of weeks and will have bloods done by BH in a couple of weeks time. Beginning to know when to trust my own instincts now. Also think that Mercury Pharma wasthe cause of Candida and that is why I have not been converting very well. Doing Candida diet (seems like forever) and having Bicarbonate of Soda as per research by UCL Southampton some years ago. Seems to help. This research was done via the Candida Society, which is now disbanded.

  • I hope they do an MRI and other testing, to see what other hormones are missing and why the pituitary isn't functioning correctly.

  • Hi faith, I did the MRI on pituitary, doctor says, it looks normal structurally. I agree with you l should do the other hormones but right now focusing on hypothyroid symptoms. Thanks for your suggestion.

You may also like...