THE THYROID: LET'S START WITH THE BASICS
Our thyroid is a butterfly shaped gland that lies against our windpipe in our neck. Though small, it has a mighty role in the body: Regulating our metabolism, supporting growth, development, steroidogenesis and neural differentiation, as well as having a say in most tissue activity. It's no wonder when this gland starts over or under-functioning that we notice a shift in well being pretty quickly.
The thyroid hormones
First up, let me introduce the thyroid hormones. We have TSH, T4, T3 and rT3.
Thyroid stimulating hormone (TSH) is released by the brain to tell the thyroid how much thyroid hormone it needs to make.
Thyroxine (T4), our inactive thyroid hormone, is made by the thyroid gland to be peripherally converted into our active thyroid hormone, T3.
Triiodothyronine (T3), our active thyroid hormone, is converted from T4. This hormone acts on tissues to increase their activity. The thyroid gland also makes some T3, though it makes 17x more T4. In someone who is replaced with thyroid medication (i.e. thyroxine), very little if any T3 will be produced by the thyroid gland. The amount of T3 in the body = how hard the body has its foot down on acceleration and the speed it is running at. T3 is what feeds back to the brain to let it know the body has enough, it sets our metabolic rate and thermogenesis. It will affect the motility in our gut as well as red blood cell production.
Reverse triiodothyronine (rT3) is a deactivated thyroid hormone, where T4 is diverted away from T3 production. This is a very protective mechanism of the body to not allow excess levels of active thyroid hormone. It can be elevated during stressful periods and is highest in pregnancy (where it’s too scary to have too much T3). Where T3 is considered the accelerator of the body, rT3 is considered the brake.
Dysfunction
Our thyroid can go into over or under function. In over function, we noticed increased heart rate and sweating, palpitations, anxious feelings, excessive unexplained weight loss, diarrhoea—basically everything speeds up in the body with an increase in T3, our accelerator. In under active function we notice hair loss, unexplained weight gain or inability to lose weight, depression, fatigue, cold intolerance, constipation, dry skin, infertility—basically everything slows down in the body with a decrease in T3.
thyroid labs
Understanding our thyroid labs is immensely important for specificity around what our thyroid is up to. The biggest issue with thyroid disorders is that the lab ranges for diagnosing hyper- and hypothyroidism are huge. This is not representative of how sensitive this gland is. We must be aware that diagnosing a disease state vs. feelings of wellbeing are not the same thing. We can be on the trajectory toward hypothyroidism and feel the effects much before we are within the ranges for medical diagnosis.
If we were to use our accelerator analogy, every 1.0 pmol/L increase in T3 is like going 10km faster. The difference between going 30km and 50km is palpable. And, this is like a T3 reading of 3 pmol/L vs. 5 pmol/L. You are going to feel incredibly different (better with a reading of 5, though if it starts to go too fast—as in hyperfunction—it might feel like you’re going 70km in a 50km zone).
Then we need to consider that we need to see the full picture. Ordinarily, our thyroid stimulating hormone (TSH) will be the only parameter tested on bloods. This is used to discern if there is anything astray with the thyroid. TSH range is 0.4-4.0, which when we are talking thyroid and subtle shifts = huge sensed change, that is a lot.
When I have a patient in clinic, I like to see TSH between 0.5 and 1.5. Of course, there will be people that feel okay and have euthyroid/normal function on a higher TSH, however, anything outside that range raises my suspicions and I want to know what T4 and T3 are up to.
The next hormone that may be tested is T4, and again, this can tell us very little about the activity in the body. It's just how much T4 is being made. What we really want to see are T3 levels and how much active thyroid hormone there is in the body to act on tissues. Expected conversion of T4 to T3 in a non-replaced person is 3:1. So, if we see a beautiful T4 of 15, we would more or less want to see a T3 of 5. When we see a lovely T4 level, but low T3, we are looking at under conversion (this is very nutrient dependent and so deficiencies are suspect).
OPTIMAL THYROID RANGES
TSH: 0.5 - 1.5 mIU/L
T4: 14 - 17 pmol/L
T3: 4.5 - 5.5 pmol/L
Please note: This is general information and these ranges are what have been observed in clinic to be the range in which the majority of people feel their best. However, we are all individuals and factors such as age, gender and pregnancy status can all play into what would be the most optimal level for a specific individual.
HOLISTIC THYROID MANAGEMENT
The thyroid does not work alone! And so if there is some kind of dysfunction, it is good to understand what might be happening with the big managers of the thyroid—adrenal glands, fat cells, reproductive glands, brain, and immune system. These will ‘read the room’ so to speak, and then feed information to the pituitary and hypothalamus (brain), that directs the thyroid on what to do next.
In this way, it is so important to understand thyroid dysfunction within a holistic scope—Do we need to address stress? Has there been a drastic change in diet? An acute illness? Has the immune system gone rogue? Currently pregnant? In postpartum? What’s nutrition like? Are we getting enough of the cofactors for making T4, as well as converting T4 to T3?
There is always lots on my radar!
Stay tuned for the next instalments of the thyroid series, where we talk about the thyroid in pregnancy and postpartum, and meet Hashimoto’s and Graves’.
