Why Going by TSH Alone Is Problematic

Originally published on 12th February 2016
Last updated on 25th March 2024

Browse thyroid patient communities online and you’ll find hoards of people saying that doctors testing only TSH (thyroid stimulating hormone) is keeping many people undiagnosed, untreated or under-treated.

Why? Let’s explore.

Firstly, What is TSH?

TSH stands for ‘Thyroid Stimulating Hormone’ and is a hormone secreted by the pituitary gland. It serves as an average read out over the previous four to six weeks of your thyroid levels.

TSH is a pituitary hormone that sends a signal to the thyroid gland. It is produced by the pituitary gland.

It goes something like this (this is very simplified):

Hypothalamus -(sends signal to)-> Pituitary -(sends signal to)->Thyroid

With a healthy thyroid gland, the pituitary gland ‘knocks on the thyroid’s door’, signalling it to work and produce so much thyroid hormone.

It does this by releasing TSH. The thyroid gland ‘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 generally seen as good. A low TSH usually means that the thyroid is producing the correct amount of thyroid hormones.

TSH in Hypothyroidism

However, in a person with an underactive thyroid (hypothyroidism) and not medicated, the pituitary gland knocks on the door of the thyroid gland, trying to give instructions, but the thyroid gland ignores it. It doesn’t respond.

The pituitary gland bangs harder and louder on the door, as the thyroid gland continues to ignore it, and doesn’t produce the hormones it should be. This equals a high TSH. This isn’t good.

Bringing TSH Down

Theoretically, if you manually put the thyroid hormones your body is lacking and thyroid is failing to produce, in to your body (via thyroid medication; ‘hormonal replacement’), the TSH level will come down, as the pituitary gland doesn’t need to knock on the door so much. It can see that the body is getting the hormones it needs. So doctors generally see the TSH level being low as your body having what it needs. 

However, this isn’t always the case.

As TSH is a pituitary hormone, not a thyroid hormone, it does not tell you your actual thyroid hormone levels. It does, however, give an indication of them.

Free T3 and Free T4 need testing to check actual thyroid hormone levels and the full thyroid panel should be used as much as possible, to get the most comprehensive view of your thyroid health. 

The Full Thyroid Panel consists of:

• TSH
• Free T3
• Free T4
• Thyroid antibodies (thyroglobulin and thyroid peroxidase) where possible

(see here why testing Reverse T3 is often controversial and why I’m dubious about whether it’s truly useful. I lean more towards ‘no’, however, you will see other thyroid resources suggesting we must have it checked.)

‘Normal’ TSH Levels

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

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?

As one study states:

“Screening exclusively with TSH will result in misdiagnosis of some cases, whilst other conditions may be missed altogether (by virtue of returning a TSH result that falls within the reference range despite overt hypothalamic–pituitary–thyroid dysfunction).” [1]

You can still feel unwell with a ‘normal’ TSH level because:

• You’re on T4-only thyroid medication such as Synthroid or Levothyroxine, which does work well for many but your body may be struggling to convert the T4 (stored thyroid hormone) to (active) T3. Your body needs enough T4 and T3.
• Your Free T3 and T4 levels could be below optimal or at the bottom of the range. TSH doesn’t tell us this. 
• Your Free T3 and T4 levels could be too high. In rare instances, TSH doesn’t always indicate this.
• You TSH may be ‘in range’ but not optimal.
• You could have adrenal dysfunction (high or low cortisol levels) or low iron levels, meaning the T3 isn’t being carried to all the places it needs to.
• You have high thyroid antibody levels, which can only be picked up by testing those antibody tests shown above, or on an ultrasound (less common). Treating the autoimmune side of hypothyroidism (present in around 90% of us) can also be of importance when it comes to resolving symptoms.

Going Forward

The next time your TSH is ‘normal’ and you still feel unwell, one of the above reasons could well be why. Many thyroid patients find that whilst their TSH is OK, their Free T3 and Free T4 isn’t optimal and so they still feel unwell. You should always be working to optimise your levels. 

If your doctor won’t test a full thyroid panel, you may explore ordering your own from online lab services.

Medichecks is a popular place in the UK, where you can order the all important thyroid function test, and thyroid antibodies to check for autoimmune hypothyroidism (Hashimoto’s).

LetsGetChecked cover most countries, and offer the thyroid function test, Hashimoto’s testing and many more, all from the comfort of your own home.

Conclusion

Now you know all of this, please don’t stay undiagnosed, under-medicated or be dismissed due to just having only TSH tested. It should form part of the picture, but not all of it.

Obtain a copy of your test results and have a look for yourself. Ensure you’re having the full thyroid panel tested to get the most comprehensive view of your thyroid health.

TSH gives an indication of what’s going on, but not the full picture.

Related Post: TSH Is Still an Important Thyroid Test by Dy Henderson

Did you know that TSH alone isn’t accurate? Share your thoughts in the comments section below.

You can click on the hyperlinks in the above post to learn more and see references to information given.

See also:

The book Be Your Own Thyroid Advocate: When You’re Sick and Tired of Being Sick and Tired, which builds on this article in detail and tells you everything you need to know to become an active participant in your own thyroid health and understand what you can do to get better.

References:

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3857600/