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Thyroid UK
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Does anyone with secondary/central hypo suffer with polyuria?

I am undiagnosed at present (normal bloods!) but have been having hypo symptoms. I am being tested for all sorts at the moment, most recently serum cortisol which came back slightly on the low side. As a result I have been asked to do a 24hr urine test and I was getting concerned that the container is almost full already so went to my friend Google! It seems normal output is 400 - 2000ml in 24 hours, I'm over that already in 8 hours! It seems that one cause could be diabetes insipidus which can be caused by hypothalamic/pituitary problems. As my TSH is normal but FT4 is low I've been looking at secondary hypo but gp has said no, yet things keep seeming to point that way. Does anyone else have similar issues? And before anyone asks, no I don't drink excessively, if anything I don't drink enough!

Thanks for reading!

6 Replies

I cannot answer your question but do you have a copy of your latest blood test results? If not, ask the surgery for a copy with the ranges and post on a new question for comments. We are entitled.

We can remain undiagnosed although we have clear clinical symptoms as they only take the TSH into consideration.


I'm actually due to get more results tomorrow but my thyroid tests back in Feb were:

TSH: 2.65 (0.4 - 4.5)

FT4: 12 (12 - 22)


rayjay, clearly something is going on but your fT4 is bottom of range. Interesting at what 'number figure' would your doctor consider that you are hypo. 11? 8? 2? They really should test fT3.

The kidneys don't function very well when thyroid is low. The don't reabsorb chloride for example.

However, you can't possibly be urinating over 2,000 ml in 8 hours if you are not putting that much into the body. Otherwise you'd die of dehydration. Maybe call up the lab or the doctor's office and let them know that you are requiring another bottle?


I'm currently at 2400ml. Today I have had 2 cups of tea, a small latte, and two glasses of squash.


rayjay, you'd turn into a dessicated skeletal human. There must be times of the day when you urinate less but drink more.

I'm not saying you don't have a problem.


I am central hypothyroid. My TSH has never risen above 6.2 whilst both ft4 and ft3 were well below range.

You may read that in central hypothyroidism the TSH never rises much above 1. This however is not the case. It can be mildly elevated above the reference range and still be central.

The indication for you is that your FT4 is at the bottom of the range whilst your TSH is only mildly elevated. That indicates that the pituitary/hypothalamus is not signalling properly. Hence there is some disfunction.

You almost certainly have some element of central hypothyroidism.

Push to have further tests.

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