Anyone know of any sensible reasons why t4 would be ok but tsh really high?
It was normal for a while but tsh has increased now
He’s only 2 so can’t tell us how he’s feeling etc
tsh is 19.6
Normal range is 0.2 - 4.3
T4 is 19
Normal range is 7.9 - 28
The best way we’ve found to give him the tablets is on a tiny bit of fruit puree. It’s the only way we can get him to swallow them whole. We’re worried that the fruit puree could effect it but the doctor doesn’t seem concerned
Can you give us the actual numbers - results and ranges - please? Because 'high' and 'normal' are meaningless without them. In fact, there's no such thing as 'normal' because we're all so different. And when a doctor says it, all he means is that the result falls somewhere within the range. But that, too, is meaningless.
But, say the FT4 is around mid-range, and the TSH is over-range, that probably means that the FT3 is low due to poor conversion. But, that's just a guess. 
Updated with more information
OK, so yes, his TSH is very high.
FT4: 19 pmol/l (Range 7.9 - 28) 55.22%, which would appear to be euthyroid.
However, without an FT3 result there's a huge piece of the puzzle missing. I know they don't normally do it, and I know it's out of abysmal ignorance, but in this case it really needs to be done to find out how well his is converting that T4 you're giving him into T3. So you need to nag, bully and cajole until they do it.
Of course, it might be that his FT3 is equally normal and that the high TSH is due to essay interferance. It happens. And, if his doctors had one ounce of intelligence they would immediately have retested in a different lab. But I guess that's expecting too much. Sigh.
Oh, and don't worry about the fruit puree. If it does affect absorption in any way, that will show up on his blood test results and his dose will be adjusted accordingly.
What does really high mean? Paediatric TSH levels are higher than adult ones.
Levothyroxine is a very fussy hormone and it will really only work well when taken alone on an empty stomach with nothing other than water for 30mins to an hour after. This cant be easy with a toddler.
Have you considered liquid Levo that might be easier to administer? Your GP might be resistant to prescribe it as it is quite expensive but it would be worth a try to lower his TSH better.
Likely he would also benefit from a dose increase as his TSH is very high, would expect that to be closer to 1 or under. His FT4 is only 55% of range and probably needs to be in the upper quarter of the range.
Our worry with liquid levo was that it doesn't seem readily available and we were concerned about storage, we go on holiday a lot etc? Our Dr has said they'll give us a prescription if we want it
Certainly a while back there was quite a long period of time when liquid Levo was difficult to get hold of. I was taking it during that time and never went without, but it did mean switching brands. Things do seem to have settled down now judging by the lack of posts regarding the issue now.
You could use a syringe to give it to him which might be easier. It tastes of very little, maybe sugar water.
It may well be worth trialling it and see how it works for you. I don't believe it needs to be stored in a fridge so holidays should be fine.
The levothyroxine tablets are working well at the moment as confirmed by his fT4. The question is whether the high TSH is due to assay interference or there is some other problem such as a low fT3. I would stick with tablets at the moment simply because it's better not to introduce another variable.
His mum has been diagnosed as coeliac, if he has it too, could that hamper ft3?
No, it would only impair absorption of the levothyroxine and this looks OK. My knowledge is limited to adult hypothyroidism so I can't be certain a high TSH, normal fT4 isn't OK but I can't see how it is. I think you need advice from a paediatric endocrinologist, either from a consultation or a doctor checking with them. My best guess is it is an assay problem but an educated guess is not good enough.
Totally agree with jim. If it ain't broke, don't fix it! You'd just be making life more complicated for yourself. From my not neglige. able experience with 2 year-olds, they don't like change, and if he's happy with the fruit puree, then that's the way it should be. No point in upsetting the apple cart at this point for something that isn't even a problem.
His fT4 confirms he is absorbing the levothyroxine very well, so there’s no need to worry. You don’t have to swallow the tablets whole, you could snap them into smaller pieces or even crush them - as long as he gets almost all the tablet it will be fine.
The TSH result is strange, the most likely cause is assay interference. This could happen if he has a pet rabbit or similar! If he has had normal results in the past your doctor could check if they were from the same assay.
This is not something to ignore or be fobbed off with in someone so young. I would get the doctor to phone an endocrinologist for advice (appointments take time). The obvious thing to do is have another blood test using a different assay which measures TSH, fT3 and fT4.
The high TSH is not something to ignore but I suspect it’s just a spurious result.
High TSH, normal T4 - what next? 
High TSH and normal Free T3/T4
High TSH, normal T4
Tsh normal high t3 and t4
Low TSH High T3 Normal T4 Total Thyroidectomy
