Role of TSH after TT?

Hello all,

I have recently discovered your fabulous site and since have been reading the daily posts and educating myself. My first post is a question :

I had a TT exactly one year ago and still trying to balance out T3 and T4 (Levo and Cytomel). As I no longer have a thyroid I would have thought the TSH no longer plays a role.....? Any comments would be appreciated!

14 Replies

  • Welcome to the forum, Tigreg.

    Pituitary gland produces TSH when it detects low circulating T3 to stimulate the thyroid gland to produce more T4 for conversion to T3. When sufficient hormone is circulating TSH drops. Pituitary doesn't know there is no thyroid to receive a signal so can be used as a guide to dosing, although FT4 and FT3 are better indicators of optimal dosing. TSH may also stimulate conversion of T4 to T3 in peripheral tissue.

  • Thank you Clutter. But how can the pituitary stimulate the thyroid if there is no longer a thyroid?

  • The pituitary does the job it was meant for and sends out TSH. Whether there is a thyroid there to respond to the TSH is irrelevant. The pituitary continues doing its job anyway. It doesn't have any mechanism which says "Oh look, there is no thyroid now, so I can stop producing TSH."

  • Thanks Humanbean. My endo has just prescribed FT4 and FT3 test. He said there would be no point in ordering TSH after TT....? Does this make sense?

  • If your dose of thyroid meds is based on your level of FT4 and FT3 you are on to a winner there. You are likely to get a much better decision on the amount of thyroid hormone replacement that you need than if it was determined by the TSH.

    From what Clutter says below the TSH still has a role to play. But if your levels of FT4 and FT3 are taken into consideration then I wouldn't have thought you would have a problem.

    Lots of people who still have a thyroid would love to be dosed on the basis of FT4 and FT3 rather than TSH. :)

  • Yes, it looks like I might be on a winner. I live in France, my endo, although hesitant, did agree to prescribe T3 Cynomel. No charge by the way, but if you have to pay for it it would cost 2.75 € for 30 tablets of 25 mcg!

    On 27 April my bloods were:

    FT3. 4.21. (3.80 - 6.80)

    FT4. 15.6. (12.0 - 22.0) taking 100 mcg Levo and 12.5 mcg Cynomel. Since then I have added another 6.25 of Cynomel. Will test again in one week. Still feeling HYPO (obviously). Thanks again

  • Your FT3 is a bit on the low-side. It's not even mid-range, and most people find they need it to be up the top of the range to feel well.

    I hope your endo is aware that when taking T3, the FT4 will always be low because the body doesn't need to keep as much stored for conversion.

  • Thanks Humanbean. Love the name! Does that mean that the FT4 will keep declining as I add T3? Thanks for your reply.

  • Sorry, I meant my question for Greygoose.'!!!

  • If you click on the downward arrow next to Recommend on the post you want to change there are several options, including Edit. Once you've made your changes, don't forget to click on Edit Response to save your changes.

  • No problem.

    I Don't know how low it will get, that's very individual, but often doctors worry when it gets low - if they notice! Just reassure him, if that happens, that it's perfectly normal and doesn't mean he has to up the T4.

  • Thank you Greygoose.

  • You're welcome. :)

  • Tigreg, the pituitary doesn't know there is no thyroid so produces TSH. Although it can't stimulate the thyroid gland it can still stimulate conversion in receptor cells throughout the body which aren't affected by the lack of thyroid.

    I'm also thyroidless. When I was off thyroid replacement for 4 weeks TSH rose to 107.5. After 4 weeks on 100mcg Levothyroxine TSH was down to 0.16.

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