Thyroid UK
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Low T4, normal Free T4 and TSH for a 3 week old boy

Hi - We have a 3 week old baby boy and in his PKU tests the thyroid levels were low. So his pediatrician ordered for further tests and below is what the results came out to be:

T4 - 2.8 (Ref Range: 5.6 - 14.4 mcg/dl)

Free T4 - 1.02 (Ref Range: 0.65 - 2.30 nanogram/dl)

TSH - 2.540 (Ref Range: 0.400 - 7.590 microlU/ml)

So Free T4 and TSH seem within range, but T4 is low.

His pediatrician thinks it's okay and nothing to worry about at this point and that we'll continue to monitor and run some more tests in a month. We are just concerned as parents on what the issue could be and if there is anything we should or shouldn't do. Any help/insight would be appreciated.

2 Replies

Welcome to the forum, Lisandrewjeski.

I'm sorry you have this worry about your baby son. I know very little about hypothyroidism in babies but you may find useful information in this link

Close monitoring of your son means he will get treatment if his thyroid levels don't normalise soon to ensure his development doesn't suffer. I hope it all comes good soon.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

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Total T4 and free T4 don't necessarily go hand in hand. If your baby has lower amounts of the proteins that transport T4 round the blood, then the T4 reservoir itself will be less, so that the proteins can release the right amount of free T4 into the tissues. In brief, total T4 isn't always as diagnostic as free T4 and can mislead.

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