What are 'sub-clinical' TSH levels ?

[jaxnbreeze]

[RedApple Administrator]

Not sure I've heard of 'sub-clinical' TSH levels. Do you perhaps mean 'subclinical hypothyroidism', where the FT4 and FT3 are in range, but TSH is elevated above the range?

[RedApple Administrator in reply to RedApple]

Subclinical hypothyroidism is mentioned in the document on the main website here

thyroiduk.org.uk/tuk/about_...

Subclinical hypothyroidism (where there are elevated TSH levels, but normal FT4 levels, possibly with symptoms) has been found in approximately 4% to 8% of the general population but in approximately 15% to 18% of women over 60 years of age.

Subclinical hypothyroidism can progress to overt hypothyroidism (full hypothyroidism with symptoms) especially if there are thyroid antibodies present.

[nostoneunturned in reply to RedApple]

I am puzzled, or hair-splitting - I thought that the very meaning of "sub-clinical" meant there are NO symptoms whereas here "symptoms" has a mention in connection with sub-clinical hypothyroidism but according to my understanding the term "sub-clinical" does not apply. My understanding is from "Could it be B12?" by Sally Pacholok and Jeffrey Stuart:

"The definition of sub-clinical disease is: "An illness that stays below the surface of clinical detection. A sub-clinical disease has no recognizable clinical findings. It is distinct from a clinical disease, which has signs and symptoms that can be recognized."

[RedApple Administrator in reply to nostoneunturned]

I actually agree with you. I think the problem lies with the doctors wrongly interpreting the term If a patient is complaining of symptoms, then they should *not* be classed as having sub-clinical anything! However, when it comes to thyroid (as with B12), it seems that the average doctor only looks at the test results. If thyroid hormones are still in range, they diagnose subclinical and send the patient away.

There is a very good post on the BMJ from a member of this group who has personal experience of this. See the post from EC Elliott here: bmj.com/content/345/bmj.e75...

[nostoneunturned in reply to RedApple]

Thank you for the link. E C Elliot's experience is atrocious, numbers ruled but all was certainly not OK.

[shaws Administrator in reply to nostoneunturned]

According to Dr Toft, if there are symptoms or antibodies - an extract from Pulse:-

2 I often see patients who have an elevated TSH but normal T4. How should I be managing them?

The combination of a normal serum T4 and raised serum TSH is known as subclinical hypothyroidism. If measured, serum T3 will also be normal. Repeat the thyroid function tests in two or three months in case the abnormality represents a resolving thyroiditis.2

But if it persists then antibodies to thyroid peroxidase should be measured. If these are positive – indicative of underlying autoimmune thyroid disease – the patient should be considered to have the mildest form of hypothyroidism.

In the absence of symptoms some would simply recommend annual thyroid function tests until serum TSH is over 10mU/l or symptoms such as tiredness and weight gain develop. But a more pragmatic approach is to recognise that the thyroid failure is likely to become worse and try to nip things in the bud rather than risk loss to follow-up.

Treatment should be started with levothyroxine in a dose sufficient to restore serum TSH to the lower part of its reference range. Levothyroxine in a dose of 75-100µg daily will usually be enough.

If there are no thyroid peroxidase antibodies, levothyroxine should not be started unless serum TSH is consistently greater than 10mU/l. A serum TSH of less than 10mU/l in the absence of antithyroid peroxidase antibodies may simply be that patient’s normal TSH

[helvella Administrator]

It depends upon who is defining it!

Some would say any value over the laboratory's reference range but below 10.

Others might include elevated but within range.

Still others would say any value of TSH short of very high (e.g. 20) where the FT4 value remains within its reference range. (How you would ever find this out is a mystery. Many laboratories appear to be refusing to perform an FT4 test unless TSH is out of range.)

[Lucky23]

I was diagnosed as sub-clinical last year. My TSH was 4.50 and my T4 was normal. I had quite a few symptoms of Hypothyroid. I started on 25mg Thyroxine and now up to 75mg. I have been having symptoms for a long time but my tests always came back normal, until last year.

[jaxnbreeze]

Thanks for your replies. I was diagnosed with sub-clinical hypo. 18 months ago with a TSH of 8 everything else normal and no anti-bodies. It was first discovered about 3 years ago (TSH around 5) and I was given 25 levo but became hyper. and had to stop taking it. I believe it started with epstein-barr type virus about 10 years ago and I have been lucky that my only symptom was that I was tired a couple of times a year.

[helvella Administrator]

The other day I posted a paper about atrial fibrillation and thyroid - that was quite a significant study and it used these values for its definitions of sub-clinical, etc:

(I know it will end up all scrunched at the left end of the lines - but with some thought should make sense.)

Definitions of thyroid disease and thyroid dysfunction levels used in study

TSH (mIU/L) Free-T4 (pmol/L) Total-T4 (mmol/L)

Euthyroidism 0.2–5.0 9–22 60–140

Overt hyPO >5.0 <9 <60

Subclin hypo >5.0 9–22 60–140

Overt hyPER <0.2 >22 >140

Subclin hyPER <0.2 9–22 60–140

(TSH) level dependent thyroid dysfunction definitions

TSH F-T4 T-T4

Euthyroidism 0.4–5.0 9–22 60–140

Hi-norm euthyroidism 0.2–0.4 9–22 60–140

Subclin hyPER (reduced TSH) 0.1–0.2 9–22 60–140

Subclin hyPER (suppressed TSH) <0.1 9–22 60–140

Rod