Thyroid UK
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Shocked by my very low thyroid TSH result. Help!

After reading posts on this forum I have, for the first time, requested a copy of my recent Thyroid function test results from my GP and I am shocked and confused. The shock comes from a Serum TSH reading of <0.01mu/L (0.27-4.2) and confusion that the unit measurement is mu/L rather than the unit mlU/L normally seen.

Serum free T4 level-13.1 pmol/L (10.0-21.0)

Serum free T3 level 3.7 pmol/L (3.5-6.5)

Serum ferritin 205 ug/L

Serum vitamin B12 376 ng/L

What does this abnormally low TSH count indicate? I am taking 100mcg T4 and 20 mcg T3 (10mcg am and 10mcg pm) daily for my hypothyroidism diagnosed 8 yrs ago. I had a goitre and thyroidectomy at the age of 19, 52 yrs ago. I am currently feeling lethargic, lacking stamina, hair thinning and putting on weight.

I also take Premique hormone replacement therapy and Adalat for moderatly high blood pressure. Please help me make some sense of this.

9 Replies

Your B12 level is too low. You need to get it up to help your thyroid hormones work effectively. Supplement with methylcobalamin which you can get from Amazon. (Either Jarrows or Solgar.) As far as the doctor is concerned your B12 is "normal" so s/he won't prescribe anything as they are not allowed to under various NHS clinical guidelines. However for thyroid hormones to work effectively you need it at the top of the range. (I know you haven't given a range but it's in the same units my tests are in.)

If you haven't had your folate and vitamin D tested in the last 2 years get them tested.

In regards to the TSH don't worry about the units. Giving the range means others can work out what level you should be at. (I'm confused as you have had a thyroidectomy)



I think mu/L is the same as unit mlU/L- meaning 0.001 or 1/1000 ... just one is american.

TSH and T4 would be expected to be low when medicating T3 as the pituitary senses thyroid meds and gives up ! ... I medicate T3 and my TSH is suppressed & just fine .

T3 is the all important active hormone and a low level would account for your hypothyroid symptoms ... ... you need a dose increase of T4 to 125mcg a day ? ? ... this will increase the T4 and T3 levels by additional conversion. .

B12 is optimal at 1,000 according to PA Society. Supplement 1,000mcg methylcobalamin and take a B Complex vitamin to keep the other B vits balanced.

Ferritin is fine. As Bluebug asked ... have you had folate & Vit D tested ? ? >..?

High BP could be down to low thyroid hormone replacement ? ? ... When I optimised mine, my high BP corrected itself.

If Premique suits you, then stick with it (I have done very well on bio-identical HRT hormones) but be aware that alterations in T4 and T3 can result from higher levels of oestrogen, that increases the serum thyroxine-binding globulin concentration. This slows thyroid hormones entry into the cells (including pituitary) and may lower T4 & T3 levels, inducing hypothyroid symptoms. Doctors should know of this and be prepared to give a compensating dose raise.



Absolutely right that mu/L is the same as mlU/L.

They both mean "milli-International Units per litre". They use a capital letter U to distinguish it from u (which is used for micro). They sometimes, but not always, drop the I (capital letter i) because it is so easily confused with l (lower-case ell) and 1 (numeric one).

And they use L (capital ell) for litre even thought the scientific agreement is l (lower-case ell) because it can so easily be confused with I (capital i) or 1 (number one).

All that to get to my point - this isn't a USA-ism, even if one form is more common there. :-) :-)


Haha ... what a loooooooong winded expla ! ! ! ....

Much prefer mine ... but mucho gracious senor ...

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I would avoid any iron containing supplement, personally. Your ferritin is quite high enough.

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tsh is that low with t3 meds..mine is 0.006, at my last check, which is much lower than yours.


Why would you be worried by low thyroid stimulating hormone (TSH)? Low is an indication that you are getting enough of your thyroid hormones. High TSH is an indication that there is a problem. However, you should go mostly by symptoms.


Well, not really, no. Because she hasn't got enough T3. It's just that taking any amount of T3 can suppress the TSH. But, that's perfectly normal, and not a problem. :)


As most are saying, the TSH is not very important, although your doctor will probably treat it as if it is. The freeT4 and freeT3 are more important, as these are measures of the hormone that's in your blood. Yours are looking a little low, ideally freeT4 should be in the upper quarter, and freeT3 should be in the upper third. Yours are bumping along the bottom, so an increase would improve things.


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