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Why TSH isn't enough for thyroid testing

Thyroid Stimulating Hormone (TSH) is what most of us would have had tested by a GP when we’ve had our thyroid checked. If we present to the doctor with fatigue or difficulty losing weight or maybe our mother had an underactive thyroid, they will usually run a TSH blood test to see what the thyroid is up to.

TSH is made in the pituitary gland in our brain and it will signal for thyroid hormones to be made. TSH is therefore technically a brain hormone, it shows what the brain wants the thyroid to do but not necessarily what the thyroid is actually doing. I’ve seen countless patients with “normal” TSH levels but when we dig a little deeper, other hormones reveal otherwise.

When TSH is released it will trigger T4 to be made. T4 is the starting block and needs to convert into T3 to exert the actions around our body synonymous with the thyroid (eg: metabolism and energy). Sometimes our T4 is “normal” but our T3 is low which means that we have an underactive thyroid but it would most likely be missed on a blood test.

Thyroid testing without looking at thyroid antibodies (anti-TPO, anti-TG, and TRABs) also only gives one piece of the puzzle. There are many things that can be done to bring hormones back into balance but if there is an autoimmune presence such as in Hashimotos or Graves, it is a whole different way of treating and the usual methods won’t be enough.

Reverse T3 (rT3) is another helpful marker to test as it can tell us a lot about why the thyroid may not be producing adequate hormones. It will be elevated when there is stress in the body often from infection, injury or inflammation.

Other important tests include Vitamin D, iron, iodine loading, and looking into zinc, selenium and heavy metal levels as inadequate or excessive amounts of these can influence thyroid function. So as you can see, it’s not as simple as just looking at TSH!

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