Confused about urine test

[hoalarg]

How can my T3 be upper part of range but my bood test showed FT3 low? This is confusing. Has anyone else had this? Do I go with blood test results?

[SeasideSusie Remembering]

hoalarg Because they don't measure the same thing. You can't compare them.

The blood test is showing what hormones are in your blood at the second it is drawn. Total T4 shows how much thyroid hormone is bound to proteins. Generally only seen in private tests and when it's low the thyroid is struggling. Free T4 and Free T3 show how much hormones are not bound to proteins and again will be low when the thyroid is struggling. If FT4 is a fair bit higher in it's range and FT3 is low in it's range that generally indicates poor conversion.

The urine test shows what hormone has reached your cells over the 24 hours of collection. It is testing the metabolites (breakdown products) passed in urine.

Urine tests are good for showing how well T4 is converting to T3 (and your results show that good conversion seems to be happening) but it isn't a particularly good test for diagnosis.

What are you looking for - diagnosis or conversion?

[hoalarg in reply to SeasideSusie]

Thanks for the message. So it's not for diagnosis of hypothyroidism? My blood test showed TSH 8.2, FT4 just below range and FT3 low in range. Dr P ordered test and I was expecting it to show similar but from what you have said it won't do that. So it is mainly used for conversion readings?

[SeasideSusie Remembering in reply to hoalarg]

hoalarg No, it's not a good test for diagnosis (but it is still a useful test as it's all part of the bigger picture).

The urine test is only for measuring the amount of hormone that has reached the cells, it can't measure TSH which is important to tell us whether we have enough thyroid hormone for our thyroid to be working properly or whether the pituitary is detecting there isn't enough, when looking for a diagnosis.

Looking at your blood tests, your TSH is quite a way over range so your pituitary has detected you don't have enough of your own thyroid hormone so it's sending a message to the thyroid to make some - Thyroid Stimulating Hormone - so your TSH is high. FT4 is below range so whatever Total T4 (bound to protein) there is (if it was measured it was probably low in range) isn't making much FT4 as it is under range - so TSH and FT4 are telling you that you are hypothyroid.

The urine test will show how much T4 and T3 are getting through to the cells as well as showing how well, or not, you are converting.

As an example of how useful the urine test can be, I was diagnosed hypothyroid over 40 years ago, last few years struggling with symptoms but on a high dose of Levo (up to 200mcg) with suppressed TSH and very over range FT4 (up to 30 with range of 12-22), FT3 never more than 40% through range. No amount of Levo was helping, GP not worried about suppressed TSH but panicking about FT4, but couldn't/wouldn't help, so I had to do my own research.

My urine test came back with T4 39% through range but T3 minus 6%, so not​ much T3 getting through to the cells, so little conversion happening despite what the blood test was showing.

Over 12 months of adding T3 to Levo and tweaking doses, checking with blood tests and the occasional urine test, my last urine test showed that T4 was 46% and T3 50% through their ranges.

Without the urine test I wouldn't have known that virtually no T3 was getting into my cells and I don't like to think what would happen if I had to stay purely on Levo. So it's a very useful test to show what is getting into the cells and being used.

As Dr P ordered the test, did he tell you why and what he was looking for? Have you communicated with him about the results?

[hoalarg in reply to SeasideSusie]

Thanks again. No, I have just got them and will speak to him next week to find out. So my urine test is showing that hormones are reaching the cells so maybe I have a pituitary problem? Would you say the urine results are positive? He thought my thyroid had good capacity as I had good reflexes. He wasn't sure why TSH was high but thought adrenals were affecting thyroid.

It's quite a complex thing to get my head around.

[SeasideSusie Remembering in reply to hoalarg]

hoalarg I don't know enough to say whether you might have a pituitary problem. All I know about that is if TSH is low along with low Free Ts then that points to secondary/central hypothyroidism where the problem may lie with the pituitary or hypothalamus.

Your urine test shows that T4 and T3 are getting through to the cells, with plenty of T3 there.

Wait and see what Dr P says.