Unmatching TSH and T3

[Midlands Mum]

I am hypothyroid diagnosed by NHS endocrinologist in 1998 and subsequently managed by NHS GP . I have thyroid antibodies and my age is 71. This January my FT4 is 25.5 and TSH 0.01. My levothyroxine was gradually reduced from 200mcg to 150mcg a year ago. Last July my T3 was 3.5 and the lab report said Low FT3. (It is rare for our lab to test FT3 even when a GP requests it, which is why that is my only record of an FT3 test. ) Can you please explain the significance of my low T3 and tell me if my TSH 0.01 is likely to change, having been 0.01 for 12 years. I have no osteoporosis and must point out that I was maintained on 200mcg over a number of years to control my symptoms including bradycardia. Over that period my TSH remained within normal limits. But then my T4 unexpectedly rose suddenly to over 30 for no obvious reason which is why my thyroxine was gradually reduced.
In anticipation thank you for your expert's help, Diana

[Dr Petros Perros]

Dear Diana,

I wonder if you are taking other medications (besides thyroxine)? Sometimes they can influence FT3 levels. Thyroxine requirements tend to decline as we get older, so it is not surprising that the dose of your thyroxine required readjustment. The levels of thyroid hormones in people on thyroxine, can also be influenced by taking the tablets with food or other tablets. Your best chance of staying healthy would be with a serum TSH within the normal reference range.

[Midlands Mum]

Dear Dr Perros,
Thank you very much for your reply.
I always allow time between levothyroxine and food and other medication and realise we are likely to need less thyroxine as we reach 70. Another reason why I need less thyroxine is losing 2 stone weight with a calorie controlled diet. My only other medication is bendrofluazide 2.5mg daily since 1977 for swollen legs. My BP is always normal, so are all other blood test results.

After 12 years of being stable on 200mcg levothyroxine with FT4 within the normal range and TSH 0.01 I suddenly went into AF and found my T4 had suddenly soared to over 30. A few weeks after reducing my dose I became ill enough for my GP to allow me to gradually titrate my dose back to 200mcg and a normal quality of life . But after a few months AF recurred. It again reversed after several days. As T4 had suddenly become 30+ again my only way forward was to reduce thyroxine, especially as even a tiny dose of sotalol/beta blockers over- sedate me, so my cardiologist prescribed one 40mg sotalol tablet daily only while in AF. He was convinced my T4 level caused AF. A subsequent echocardiogram is entirely normal. A bone scan shows no osteoporosis.

I have been very unwell between Weeks 5 to 8 each time I reduce thyroxine by 25mcgs but have now learned from experience that I then very gradually improve.

I have found when I take thyroxine at noon my energy lasts beyond 3pm, which is the most enormous improvement! Of course that means I take my dose hours after breakfast and other medication, and an hour before lunch, which may contribute to the improvement.
Very recently I reduced thyroxine again and am now taking 125mcg

Dr Perros I would be very grateful to know if you think my low T 3 has any significance?
Also having reduced thyroxine from 200mcg to 125mcg Is my TSH 0.01 at all likely to change, bearing in mind l have had TSH 0.01 for 12 years?
Thank you again for taking the trouble and giving time to answering me,
Diana

[Dr Petros Perros]

Dear Diana,
I don't feel that I can give you any more specific advice on the basis of electronic exchanges. If you are concerned and you don't feel right you have a valid reason to bring it to your attention of your GP. If he/she is unable to address your concerns adequately you have a valid reason to request to be reviewed by an endocrinologist.

bw

P