Thyroid UK
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Overt/subclinical hypothyroidism?

A couple of people have quoted the NICE guidelines on hypothyroidism recently, which is good ('official'!) material to have to have to hand when discussing your condition with your doctor. But there are sections on 'overt hypothyroidism' and 'subclinical hypothyroidism' so I presume it's important that you understand the difference and which guidelines apply to you.

Can someone give an explanation of the difference please?

(Thank you to the person who explained to me on my post, but it might be useful for others and I don't want to try and explain and get it wrong!)

5 Replies


Subclinical hypothyroidism is when TSH is between 5-10 with FT4 in normal range. Subclinical should mean asymptomatic, a fact doctors seem to ignore.

Overt hypothyroidism is when TSH is >10. FT4 will be low in range or below range.


The key point is that if you're in the 5 to 10 range on tsh and having symptoms then they're supposed to trial you with Levo to see whether it helps.

For those that have tsh below 5 but ft3 and ft4 in the low or below range look at the NICE guidelines on secondary hypo. I wasn't diagnosed for 6.5 years because my Tsh was low (1.2 ish most of the time) but my ft3 or ft4 were consistently below the range or on two occasions were 0.1 above the bottom end of the range. My symptoms screamed hypo (huge weight gain on a below 1500 calorie a day diet, sleeping 12 to 15 hours per day, so cold that a roaring fire, two hot water bottles under a snugpak coat plus blankets couldn't get me warm, high cholesterol, liver enzymes out of wack, constipation) but this, and the family history of thyroid issues (I was at 47 the only female on my mother's side of the family that allegedly had a fully working thyroid, my aunt, gran and female cousins were all diagnosed hypo in their mid 30s but I didn't find out that this was secondary until after my eventual diagnosis! My mum is hyper but she always has to be different....) didn't mean that the quacks at my previous GP surgery thought that this might be the problem (instead they determined that my food diary was a tissue of lies, I was causing my own symptoms by being so fat and then moved onto assuming I was an alcoholic that was lying about not drinking anything...)

So, read and print the NICE guidelines and batter your doctor with them. I was diagnosed within 5 mins of my first appointment with a new GP practice based on my symptoms backed up by my bloods....


Thank you - I have the NICE guidelines (and a few other things!) at the ready for my doctor's appointment this coming week...


Just for clarity - this does not affect the basic idea of using this material - but they are NOT official NICE Guidelines. There are no full NICE guidelines for hypothyroidism and hyperthyroidism. These are Clinical Knowledge Summaries which started quite a few years ago. They have been adopted by NICE for hosting and maintenance purposes but do not have the full weight of official NICE guidelines.

This link gives you all NICE mentions of "thyroid":

You can change the search term to hypothyroidism or hyperthyroidism, if you wish.


Thank you hellvella, good to know, especially if I have to use it.


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