How did you find out what blood test results should be?

[Hattie87]

Hi, so this is mainly to the people who know about what your blood tests results should show. How do you know that T3 should be on the higher end? Where did you find out your information?

Are there any good sources/papers/studies? (Ideally relaing to T3) Anything really that I could show to my doctor next times I go in.

Thank you!

[jimh111]

fT3 and fT4 'should' normally be mid-interval, this is where they are in the general population.

However, many patients on these forums find they need fT3 in particular to be higher. This is not normal and so carries risks but the alternative in many cases is a life of hypothroidism which in itself carries risks. I would always advise taking the minimum hormone that resolves your symptoms without any signs of thyrotoxicity. This is an imperfect solution but the best we have as endocrinologists have not bothered to find out why some patients need these higher doses. I don't know of any studies that show higher fT3 levels are required for some patients let alone explaining why.

[Hattie87]

Thank you. My T3 levels are midway but still feel all of the symptoms. How did you find that information out? My doctor asked why I think I need my levels adjusted so would like to have some studies or something from an expert to show him. Thank you!

[Beachytoes2u in reply to Hattie87]

Great question👏 I also want proof to show my dr., where my blood levels are "best at" trying to remember everything going to appointment, then facing that scale😲can freak anyone out! Then to quote facts to a dr., who will be defensive, right away! A actual report would be great, thank you for asking!!👩‍🚀

[Hattie87 in reply to Beachytoes2u]

Exactly! Hopefully someone replies soon

[jimh111]

Patient experience shows that many do need levels that are above normal. You could use this article from an endocrinologist who was a former president of the British Thyroid Association rcpe.ac.uk/sites/default/fi... . I actually think the article has a number of errors, but you don't need to mention that to your doctor!

[Hattie87 in reply to jimh111]

Thank you! What are the main errors? (just so I know)

[jimh111 in reply to Hattie87]

The major point is that Dr Toft and all his colleagues always assume that they are always treating primary hypothyroidism.

Many patients have a down-regulated hypothalamic pituitary thyroid axis which means their pituitary responds inadequately to low hormone levels resulting in a TSH which is lower than expected. This has consequences for using TSH as a marker of hormone activity and has effects on deiodinase (conversion of T4 to T3). It amazes me that endocrinologists don’t ask the question ‘do TSH, fT3, fT4 look consistent’ before relying on TSH.

Endocrinologists also ignore the possibility of endocrine disruption. Endocrine disrupting chemicals (EDCs) can disrupt peripheral hormone action with little or no effect on the pituitary leading to hypothyroidism with normal blood test results.

Most of the article is good provided we assume it is only dealing with primary hypothyroidism. I’d challenge the last two recommendations.

Prescribing LT4 with TSH suppression does lead to higher risk of atrial fibrillation (I’d have to double check). The reference to ‘unequivocally normal T3’ is double edged. It seems to be saying provided fT3 (I assume by ‘T3’ he means fT3) is within its reference interval all is safe. I would disagree, a high fT3 and fT4 is not always safe. It also seems to be saying you should never let fT3 go above its upper limit. For some patients this is necessary.

Dr Toft recommends prescribing a combination of levothyroxine and liothyronine provided serum TSH is normal. This assumes the pituitary is responding normally and that there is no endocrine disruption. Patients who require more than 10 mcg liothyronine are most likely to have a form of hypothyroidism that is not just primary hypothyroidism with or without DIO2 polymorphisms. The thyroid secretes 6 mcg T3 daily, taking 10 mcg L-T3 will more than make up this loss. The recommendation to keep TSH normal is not evidence based. There are no studies that show TSH is an accurate marker for thyroid hormone activity. There are studies showing a link between a suppressed TSH and atrial fibrillation but these look at patients across the board, they do not look at patients whose TSH is suppressed out of need to resolve refractory hypothyroidism.