Low TSH

[Countrylou]

I have a low TSH and low T4. (TSH hovers around 0.2) I’ve been on 75mcg Thyroxine for 20 years. My blood levels continue to go down but GPs have been instructed to only consider the TSH and not T4 therefore when I have my bloods done and go to my GP they are keen to reduce the dose. I tried this once and after 2 weeks I couldn’t get out of bed and was crying all the time, I promptly went back to my original dose.

My question is: if the body is used to taking thyroxine over a length of time (in my case 20 years) how can the pituitary gland suddenly gear up and produce my TSH if there is less thyroxine being taken?

Also: even though I feel tired all the time and have some under active thyroid symptoms I have noticed my pulse is higher during the night (I have a Fitbit!) and I’m very hot, I am also exercise intolerant, My heart beat is pounding during mild exercise where I was once very fit.

I am 60 and due to a surgical menopause at 45 I have had an oestrogen patch for 15 years.

I would appreciate any comments on this please

[jimh111]

Q. My question is: if the body is used to taking thyroxine over a length of time (in my case 20 years) how can the pituitary gland suddenly gear up and produce my TSH if there is less thyroxine being taken?

A. I have to go from memory because I can't find the study but the pituitary is able to respond if TSH has not been suppressed. If TSH has been suppressed it is able to respond in some people and not in others. It often recovers after a few months and there tends to be a rebound, TSH jumps up a bit and then settles down to normal. In your case a TSH around 0.2 is not suppressed so the pituitary should be OK.

If the TSH is not reflecting your thyroid hormone levels then the doctor should not be using TSH as a marker for thyroid status. It would really help if you could post your actual results here although ideally they would include TSH, fT4 and fT3. It looks like you are still quite hypothyroid and being under-medicated.

[Countrylou]

Thank you Jim

I struggled to attach a photo, the results from November are added but I think it might be on an edited post 😳

[jimh111 in reply to Countrylou]

Having seen your results they look reasonably OK if you feel well on this dose. If you were to reduce the dose I think you would become quite hypothyroid. Your low TSH with slightly below average fT3, fT4 is unusual. If you still don't feel well I would ask for an increase. Your TSH is not reflecting your hormone status so it doesn't make sense to use it for titration.

[Countrylou in reply to jimh111]

That’s what I thought, the TSH has never been high, always hovering at the edge of normal (on the low side) this is why I think it will not respond to less thyroxine in the blood.

I shall keep to the 75 for now and have my bloods done again in November, I know the pressure will be on to reduce the dose so I will get a few months grace and no way will they increase! thank you Jim