Question for my own knowledge based on tsh

[Irishjen]

Hi folks, this is a question just out of curiosity. I've been reading some comments on a Facebook page and people are talking about low tsh meaning over active thyroid even though the persons t3 and t4 were in range. Does a low tsh automatically mean overactive? Or is overactive not when the t3 and t4 is high regardless of tsh

Also, my own tsh last time i checked was around 0.25 or 0.28 cant remember exactly but that isn't really that low is it? i

Also in terms of tsh is there a massive difference in say a tsh of 0.01 than say 0.25. Would a tsh of 0.01 and a t3 and t4 in the middle of the range not mean the person is possibly hypo than hyper based on the t3 and t4.

Thanks

[Clutter]

Irishjen,

If someone is hypothyroid they cannot be 'overactive' but they may be overmedicated if TSH is too low and T4 or T3 are too high.

TSH 0.25 is low. The TSH range varies and if your range starts at 0.20 then 0.25 is in range. If range starts at 0.35 then 0.25 is below range. TSH < 0.1 is considered suppressed. I personally don't think low or suppressed TSH is important and that it is FT4 and FT3 which matter. Some people need FT4 over range to deliver reasonable FT3 and that will probably suppress TSH. It is generally thought that FT3 should remain within range.

Read Treatment Options in thyroiduk.org.uk/tuk/about_...

[Irishjen in reply to Clutter]

Thanks for the reply. Do basically ft3 and ft4 is more important than the tsh result. When people talk about a low tsh automatically meaning hyper it makes me a little anxious because my private endo and nsh endo think 2 different things and sometimes I question who is right. 😙

[Clutter in reply to Irishjen]

Irishjen,

TSH is a pituitary hormone. It rises in response to low T4 and T3 and drops when the pituitary detects sufficient circulating T4 and T3. In my opinion TSH isn't very helpful after initial diagnosis and it is better to determine whether someone is overmedicated by looking at their T4 and T3 levels.

[Irishjen in reply to Clutter]

My tsh was low to start with before taking good thyroxine. Will be interesting to see what my next lot of bloods say. Still eat days for me on thyroxine but I do feel brighter but at times maybe a little stimulated

[Clutter in reply to Irishjen]

Irishjen,

If TSH was low and FT4 and FT3 were low at diagnosis it is likely you have secondary/central hypothyroidism. If so, TSH isn't a reliable indicator at all and FT4 and FT3 are the only measurements you and your doctors should be taking notice of.