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Understanding TSH, a key thyroid hormone

Understanding TSH

When the thyroid gland isn’t working optimally, it affects your whole body—from your bowels to your brain (think brain fog), to your body temperature, energy levels and body shape and size. Troublingly, thyroid challenges are very common, particularly among women. And all too often this results in unnecessary suffering when these challenges are either not identified or not appropriately supported. 

If you’ve ever been concerned about your thyroid, it’s likely that you have had a blood test to check your TSH levels.

What is TSH?

TSH stands for Thyroid Stimulating Hormone and it is commonly tested in the blood to check for thyroid issues. Often it is the only parameter that is tested when someone initially presents to their medical professional with symptoms of thyroid dysfunction. This is somewhat problematic, as there are a number of other blood tests that can help to provide a more comprehensive picture of what’s going on—more on this later. 

While TSH is used to assess thyroid function, it is actually a hormone that is made by the pituitary gland in the brain, not the thyroid gland itself. Its job is to talk to the thyroid gland to tell it whether to ramp up its production of thyroid hormones (T4 and T3) or whether it needs to slow down the production of these hormones.

What does high TSH suggest?

When blood levels of TSH are high, this essentially means that the brain is needing to talk much more loudly—perhaps it’s yelling—to the thyroid gland to make more of its hormones. It usually does this when there are not enough thyroid hormones in the body. In other words, the thyroid may be under performing or underactive. The clinical name for the latter is hypothyroidism.

What does low TSH suggest?

When TSH is low, this suggests the opposite—the brain has lowered its communication to the thyroid gland to a whisper, because there may be too many thyroid hormones circulating in the body already. This can suggest that the thyroid is overactive. The clinical name for this is hyperthyroidism.

An additional consideration

If TSH is within the ‘normal’ range, often you will be told that there is nothing wrong—which can be incredibly frustrating if you’re experiencing a whole host of symptoms that may suggest otherwise. The reference range for TSH is broad, so it’s important to be aware of where you sit within the range—you can ask for a copy of your blood test results so that you (and your practitioner) can have a look at this. For example, if your TSH value is sitting within the range but right up near the upper limit—and you are experiencing symptoms—it’s likely that it’s underperforming and optimising thyroid function will be highly beneficial for you and will lead you to feel much better. 

What other tests are available to assess thyroid function?

In addition to TSH, other blood tests that can be used to assess thyroid function include T4 (inactive thyroid hormone and the precursor to T3)and T3 (active thyroid hormone), reverse T3, and thyroid antibodies. Interpreting these alongside TSH can help to provide a clearer picture of how your thyroid is functioning and what (if anything) might be awry. If T4 is fine and T3 is low (or low end normal), it can be related to a selenium deficiency.

However, it’s important to be aware that your GP or medical professional may not be able to order all of these tests for you. As I mentioned, TSH is often the only marker that is tested initially by a GP, and this can be due to strict rules that they may need to comply with to order subsidised/free tests for you. There is an option, however, to pay for these tests yourself. However, if you wish to do this, it’s important to work with a qualified practitioner to ensure that the tests are conducted in the right context and interpreted appropriately—you want to make sure you are getting the most out of any tests that you invest in. 

If you are experiencing ongoing symptoms, the most important thing is that you seek support—regardless of whether your TSH has come back normal or not.

Want to learn more about the thyroid? Check out my on-demand Thyroid webinar here.

If you are experiencing unexplained or ongoing symptoms and/or you suspect you may have a thyroid problem, please consult with your qualified healthcare practitioner. It’s important to see your medical professional in the first instance to rule out any other potential conditions, as some symptoms can present for a range of different reasons.

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