Understanding T3/4

[Harley60]

Hello,

I would really appreciate anyone’s thoughts on the reading of my recent Thyroid function test. I had to battle to get the T3/4 as it’s not normally offered on the NHS. I asked for it as I have been feeling so tired and it was suggested that I look at the T3/4 as the TSH is not necessarily that helpful. Thank you 🙏

• Serum TSH level: 1.65 mU/L (normal range: 0.30 - 4.20)

• Serum free T4 level: 13.7 pmol/L (normal range: 9.0 - 19.0)

• Serum free T3 level: 3.4 pmol/L (normal range: 3 - 5.4)

[SarahJane1471]

Hello and welcome to the forum.

Some very knowledgeable people will come along soon and give you ALOT of information. Dont worry it will all seem very confusing but it’s important that you keep reading and understanding about the issues.

Good luck

[pennyannie]

Hello Harley and welcome to the forum ;

Are you taking any thyroid hormone replacement or is this your ' natural ' thyroid function status ?

Have you been diagnosed with anything ?

[Harley60 in reply to pennyannie]

Hello Pennie, I am taking 125mcg levothyroxine daily

[pennyannie]

There is no history on your profile page so can I ask how long have you been taking T4 - thyroid hormone replacement and do you have a diagnosis of a thyroid auto immune disease - commonly referred to as Hashimoto's ?

We generally feel best when our T4 is up in the top quadrant of it's range as this should convert to a decent level of T3 at around a 1/4 ratio - T3/T4 :

We also generally feel best when the TSH is down at least under 2 and probably under 1 and towards the bottom of the range when optimally medicated.

The TSH was originally introduced as a diagnostic tool to help confirm a diagnosis of hypothyroidism and was never intended to be used once the patient was taking any form of thyroid hormone replacement as then we should be dosed and monitored on our Free T3 and Free T4 readings.

Though I am fully aware that in primary care your doctor maybe only able to get run a TSH and an occasional T4 reading. and why many forum members are forced to arrange their own private blood tests.

Your T4 is currently at around 47% through it's range and your T3 struggling along way behind at around 16% :

T4 is basically a storage hormone which the body needs to convert to T3 which is the active hormone which runs the body.

One's ability to optimise and convert well the T4 into T3 can be compromised by non optimal levels of ferritin, folate, B12 and vitamin D so suggest you get these core strength vitamins and minerals tested as we can then advise as to supplementing where and if necessary.

If your doctor can't help with these extra blood tests you can do these for yourself :

If you go in to Thyroid UK - the charity who support this forum - thyroiduk.org - you can read further on all things ' thyroid ' and there is a whole page of private companies who run blood tests and you simply post the results and ranges back up in a new question/post and you will be given considered opinion.

So just to comment on the above thyroid blood tests and not knowing your medical history, you look to be under medicated, and possibly struggling to convert the T4 into T3 since we need more information to say anything with any certainty.