Thyroid UK
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As my Ferritin went up my T4 went down?


I will try to be brief and I appreciate you reading this and hopefully responding :-)

I went to see my doctor back in August (4 months ago) because I had various symptoms, extreme tiredness, feeling cold, unable to exercise, palpitations etc but my main concern was that I had lost a lot of body hair including my eyebrows!

The doctor immediately said that I had an underactive thyroid and sent me for a blood test but the result came back normal which she was very surprised about. She said that my Ferritin and B12 were low so started me on supplements.

TSH level 1.65 miu/L [0.35 - 5.5]

free T4 level 13.5 pmol/L [10 - 19.8]

ferritin level 16.4 ng/ml [10 - 291]

vitamin B12 level 225 ng/L [211 - 911]

4 months later I had a follow up test and these are the results for camparison:

TSH level 1.66 mU/L [0.35 - 5.5]

free T4 level 10.3 pmol/L [10.0 - 19.8]

ferritin level 41.2 ug/L [10.0 - 291.0]

vitamin B12 level 294.0 ng/L [211.0 - 911.0]

I was pleased to see that my ferritin has come up considerably and will carry on supplementing.

The concern I have is that the T4 has dropped. The doctor said that all results are fine and within the normal range! I pointed out that T4 is only .3 within the lower end but he shrugged and said everything is normal.

All I want is to grow my eyebrows back, I've seen 4 doctors and they just shrug and say it's just one of those things that they can't explain.

I don't fully understand thyroid blood tests but I do know that there has to be a certain combination of results. Can anyone tell me if my T4 is ok

3 Replies

No Rsm68 your FT4 is not alright.

Take a look at this link

Which mentions normal TSH and low FT4 and states:

"A normal or low TSH level usually excludes primary hypothyroidism. However, the rare diagnosis of secondary (pituitary) hypothyroidism should be considered if T4 is also low. The commonest cause of this pattern is sick euthyroid syndrome."

Maybe ask for this to be investigated, possibly a referral to an endo is necessary if your GP is out of his depth.

Have you had thyroid antibodies tested? The NHS can do Thyroid Peroxidase (TPO) but rarely does Thyroglobulin (TG) but these can be done privately with a fingerprick test at home.

For your vitamins and minerals the optimal levels recommended here are:

B12 - very top of range, even 900-1000

Ferritin - usually recommended is half way through range, a minimum of 70 is needed for thyroid hormone to work properly (our own or replacement hormone)

It is usual to test folate when B12 is tested as they work together, and folate should be at least half way through it's range.

It's also a good idea to get Vit D tested and that should be 100-150nmol/L or 50-70ng/ml.

1 like


Thanks so much for your reply.

I had Thyroid anti-bodies checked on the first blood test and they were mid range 28 (0-60) but they were not checked on the follow up test.


Once your Thyroid antibodies are tested they don't need to be retested. However you need to find out why your T4 is so low so insist on an answer for that.

Ask for you vitamin D and folate to be tested as they can cause problems with body hair as well as head hair. Though they don't effect eyebrow hair.


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