Why Going by TSH Alone Is Inaccurate

TSH is often regarded as an inaccurate way to measure thyroid function. Why?

Let’s look at TSH like this:

TSH is a pituitary hormone that sends a signal to the thyroid gland. It is produced by the pituitary gland. With a healthy thyroid, the pituitary gland knocks on the thyroid’s door, signalling it to work and produce so much of certain hormones. It does this by releasing TSH. The thyroid answers the door and does what it’s told by the pituitary by releasing the correct amount of thyroid hormone. Therefore, the pituitary gland isn’t having to knock too much, which equals a low TSH. This is good.

In a person with an underactive thyroid, like us, the pituitary gland knocks on the door of the thyroid gland, trying to give orders, but the thyroid ignores it. It doesn’t respond. The pituitary bangs harder and louder and more often on the door, as the thyroid continues to ignore it, and doesn’t produce the hormones it should be. This equals a high TSH. This isn’t good.

Theoretically, if you put the hormones your body is lacking and thyroid is failing to produce, in to your body, the TSH will come down, as the pituitary doesn’t need to knock on the door so much, as it can see that the body is getting the hormones it needs. Doctors see the TSH being low as your body having what it needs. So when you start on thyroid medication and it brings your TSH down, this what makes a doctor so giddy.

Another analogy you could use when your doctor tells you your TSH is fine, but you don’t feel ‘fine’;

Would you be happy with a heating engineer telling you your central heating is working fine, just because the thermostat reading is normal, when the radiators are cold and the house is freezing?

Having a ‘fine’ TSH is one thing, however, your body actually performing properly is another. 

TSH is a pituitary hormone, not a thyroid hormone. It does not tell you your actual thyroid hormone levels. You need Free T3 and Free T4 to check this!

-Your body could be failing to convert the T4 (thyroxine, also known as Levothyroxine and Synthroid in the UK) to T3, which makes you feel rubbish, still.

-Or, your adrenal glands could be dysfunctioning or you have low iron, meaning the T3 isn’t being carried to all your cells, organs and muscles etc.adequately. This can show as a low TSH, but high Free T3 on blood results. This is referred to as ‘pooling’ by Stop The Thyroid Madness.

Next time your TSH is ‘fine’ and you still feel poop, one of these may be why!!

You need to ask for a Full Thyroid Panel blood test to be done for a proper look at how you’re doing, but remember, it’s recommended by many thyroid patients out there to not take your thyroid meds for that day until AFTER the blood has been taken.

Many patients find that while their TSH is OK, their Free T3 and Free T4, or even Reverse T3 isn’t optimal.

Don’t stay undiagnosed, under-medicated or be dismissed due to just having TSH tested.

You can click on the hyperlinks in the above post to learn more and see references to information given, but more reading and references can also be found at:









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I also run a Facebook group, simply called Underactive Thyroid Advice & Support Group. This group is for underactive thyroid patients only, and not medical professionals or anyone else. If you have any questions on dealing with hypothyroidism, or want some help and advice, please join us. 


About Rachel Hill, The Invisible Hypothyroidism

Diagnosed with Hypothyroidism, Hashimoto’s Thyroiditis and Chronic Fatigue Syndrome (ME), as well as having Adrenal Fatigue and experience with Depression and Anxiety Disorder, Rachel Hill blogs at theinvisiblehypothyroidism.com to help others, covering all aspects of what it’s like to have these conditions. Rachel is one of the many faces of thyroid disease and she’s passionate about helping those with hypothyroidism and giving them a voice.
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2 Responses to Why Going by TSH Alone Is Inaccurate

  1. Pingback: An Open Letter: “Dear Doctor, It’s Not All in My Head.” | The Invisible Hypothyroidism

  2. Pingback: March is Autoimmune Disease Awareness Month. – Hashimoto’s Thyroiditis. – The Invisible Hypothyroidism

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