Why is my TSH so low?

I just picked up my latest blood results, my TSH is 0.08 (0.27-4.20).

I'm on levothyroxine 100mcg.

I've been suffering with returning symptoms for months ,so I expected that it would have gone up. I'm so confused about all this. I'm seeing an endocrinologist next week and want to be able to ask for whatever I need, can anyone explain why my TSH is going down?

7 Replies

  • Jackiez,

    TSH goes down when the pituitary gland detects sufficient circulating FT4 and FT3. As you don't feel well it may be worth you ordering a private TSH, FT4 and FT3 test to check all your thyroid levels. Blue Horizon Thyroid Plus 3 covers these thyroiduk.org.uk/tuk/testin...

  • Thanks Clutter, I'm hoping the Endo will be a good one, and run all the appropriate tests😊

  • Taking Levothyroxine and no T3, with low TSH and free T4 that isn't high, I think you should have your pituitary investigated.

  • I agree that's a possibility, hopefully the Endo will get to the bottom of it😊, thanks.

  • TSH becomes irrelevent at low levels. It can become suppressed no matter what hormone replacement you are on. At this level it is NOT causing your problems.

  • No, it just goes to show how useless it is to go by the TSH I suppose!

  • But if TSH is a proxy, though imperfect, for free T3 and/or T4 which you don't have test results for, you should treat out of range results with respect. In my recent experience, with a drop from 0.44 to 0.11 (lab's lower limit 0.3), I didn't get warning signs such as frequent bowel movements and tachycardia this time, but severe arm weakness, frozen shoulder and cognitive issues.

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