You have all the symptoms of a dysfunctional thyroid gland; your health care professional ordered a test and now you’re staring at a bunch of numbers trying to decipher them as if they were a cryptic crossword!
I often find myself explaining thyroid tests, so I thought I would publish this article to explain what each marker means, why you should check them and what the optimal reference ranges are to ensure your thyroid is functioning optimally.
TSH – Thyroid stimulating Hormone.
The hypothalamus is responsible for amongst other things managing hunger, thirst, sleep, hormones and body temperature, it continuously monitors the level of thyroid hormones present in the bloodstream. TRH thyroid releasing hormone is sent out to your pituitary gland if it deems energy levels are low, the pituitary gland subsequently releases TSH Thyroid Stimulating hormone which is sent directly to the thyroid to produce more T4 thyroid hormone. Consequently, your TSH level is an indication of what your pituitary gland is doing based on your hypothalamus’ feedback loop as opposed to how your thyroid is actually functioning. Due to this being a negative feedback loop the meaning of the results are generally counterintuitive and confusing.
High TSH – This can be a sign that you are under-producing thyroid hormones and that you are hypothyroid.
Low TSH – This can be a sign that you are over-producing thyroid hormones and are hyperthyroid. It can also indicate that you are on too much supplemental thyroid hormone. Supplemental T3 of natural desiccated thyroid hormone can artificially suppress your TSH, so in the absence of symptoms it could be perfectly normal.
Normal TSH – If your TSH falls within the normal reference range this can indicate that you do not have a thyroid dysfunction. However, if you have the symptoms then even if your test results indicate a normal result you may still have thyroid dysfunction.
T4 – Thyroid Hormone in storage mode.
Once TSH signals your thyroid to up the production of hormones it produces four different types of thyroid hormone = T1, T2, T3 and T4. With the primary being a storage hormone called T4. Free T4 (FT4) is unbound and circulated throughout the bloodstream and stored in tissues so that when required it is readily available.
High FT4 – Can indicate an overactive thyroid – Hyperthyroidism
Low FT4 – Can indicate an underactive thyroid – Hypothyroidism
Free T3 – The Fuel
On deciphering that each local area of your body requires more power, storage T4 is converted into Free T3 (FT3), the active form of the hormone attach to receptors inside your cells and power your metabolic processes, hence the fuel.
High FT3 – indicates your thyroid is overactive – Hyperthyroidism
Low FT3 – You may be converting T4 to FT3 very well and you could have hypothyroid symptoms even if your TSH and FT4 are with in ranged. This is one of the most common causes of hypothyroid symptoms which is often over looked in generalised NHS testing.
Reverse T3 – The Braking System.
A portion of T4 is required and used to create Reverse T3 (RT3), which like T4 is inactive. RT3 can attach to the receptors for FT3 in order to slow your metabolic processes, hence the breaking system.
High RT3 – It is probable that you are converting too much T4 into RT3 and not enough FT3, which can cause hypothyroid symptoms even if your TSH and T4 levels are optimal. Your RT3:FT3 ration should ideally be less that 10:1