Everywhere I go, someone manages to ask me a question about health, nutrition or training. One topic that comes back often is thyroid issues (especially on the sluggish side) because a lot of symptoms are well known by the general population. To name a few: low energy, unexplained weight gain, cold extremities, thinning hair, dry skin, and goiter. Often, the person I’m talking to will say that they saw the doctor, did a blood test and everything came back normal (to understand what normal means, see my article “Is your blood test normal or optimal?”). But, is the test accurate enough for a proper diagnostic of low thyroid?
But still, you have all these symptoms and the results of your lab test were normal! Let me explain what they really measure and what should have been measured. First, I’ll do a little bit of education in medical terms and second, in a more understandable way!
When the body needs more thyroid hormone, the brain will send a signal to the pituitary gland by secreting the hormone TRH. TRH will then stimulate the pituitary gland to produce the hormone T4 (thyroxin). T4 will be released in the blood stream and will be converted in part by the liver to either T3 or rT3 (about 50:50 in normal condition). rT3 is non active, it binds to the same receptors, same parking as T3. So the more you convert to rT3, the less the body produce T3 and the less it could find a parking to do its job! T4 will also be converted to T3Ac and T3S (about 20% of T4 is converted to these forms. (They will be secreted in the gut, converted by the gut flora to T3 and reabsorb)
That was the medical stuff, now the understandable part… Hockey season just started so I’ll use a hockey team to explain the thyroid functions. Here it goes:
All the characters:
Mr. TeeRH the General manager (Representing the hormone TRH in the body)
Madam TeeSH the head coach (representing the hormone TSH)
Hockey players (curiously they all have T4 on their t-shirt) (representing the hormone T4)
The hockey sticks (made out of selenium)
The puck!
Usually, the General Manager (GM) upstairs on the top office, gives directions to the Head Coach (HC) easily. They tend to get along very well. If the GM sees that not enough goals are scored, he will talk a bit louder; the Head coach will understand and speak louder to her team of hockey players. These guys become more active and shoot more pucks so more goals are scored. The GM is now happy and lifts the pressure off the Head coach who then asks players to go easy. That’s when every thing goes according to the plan. So in medical terms, if the body has enough thyroid hormones, TRH secretion increase (GM speaks louder), TSH will increase (HC speaks louder) which increase the production of T4 (more active players) that gets converted into T3 (goals), T3 scores… Oops sorry… Goes into the cell which tells the brain to reduce the production of TRH (GM calms down).
Ok try to follow me here. What if not enough goals are made and that the GM is talking louder to the Head coach who talks louder to the players but the players are not listening? The number of goals won’t increase, right? So now Madam TeeSH, the Head coach, who doesn’t want to lose her job, is now shouting at her players up to a point that she gets really loud! If you look at the issue you realize that the real reason why there are no goals is because no one responds to the Head coach (TSH)! That is exactly how the medical teams will evaluate your thyroid function. Is the body shouting too loud at the thyroid? Yes: you have issues… No: you are normal (if within normal range).
Is it the only possible reason why there is no goal being scored? What if the players are actually hearing the Head coach but are too stressed out (high cortisol) and shooting pucks that are easy to stop by the Goalie (rT3), what if the hockey players can not shoot at all because some of them don’t have any selenium hockey sticks (mineral deficiency)? What if they shoot but the Goalie put extra padding so there is no place left to score (environmental pollutants)? What if they try to push the puck behind the net so it bounces back in the zone to be scored but doesn’t come back (T3Ac and T3S into T3)? It’s legit to ask all these questions, right?
So what does it mean for you? If you did a blood test and your doctor only asked for TSH, you will only know if the body is talking too loud to your thyroid to produce the hormone T4. (That’s why if you have low thyroid function, TSH will be high, not low).
The hormone T4 is made out of Tyrosine (an amino acid, part of protein) and Iodine (a mineral). When stressed out for a while, the body can deplete his tyrosine level and that could impair the T4 production. So by asking T4 blood level on top of TSH level, you would get more information of either nutrients depletion (tyrosine and/or Iodine) or a real thyroid issue. You will not be able to differentiate a low level of tyrosine from an exhausted thyroid, but at least you know that if TSH is high and T4 is low you should do further investigations. What if TSH is high and T4 is high? Then the body is asking the thyroid to produce T4 which it does wonderfully, but why is the body still asking for more? Because the cells may not get the T3 they wanted so are still asking the brain to send more! So it would be a good idea to look at T3 levels.
T4 is converted in the liver to T3; it is 4-5 times more active than T4. This process is dependent of proper selenium level in the body. So having a high T4 with low T3 could mean a deficiency in selenium or the body is switching the conversion of T4 to rT3. So now you know that a very basic test shouldn’t have only TSH but include levels T3 and T4 as well.
From a functional medicine point of view, we could investigate further by measuring other hormones like rT3 (Note that this test is not always accessible in hospital laboratories, so more advanced labs are necessary). We could look at iron level that is also mandatory from proper thyroid function. We could look at anti-bodies like anti-TPO and anti-Thyroglobulin, to see if the immune system is attacking your own thyroid gland! We could look at adrenal functions, because of the close relation they have with the thyroid. Other things like environmental pollutants can be measured as well and should be considered too and one could argue that thyroid function should be evaluated by the symptoms, not the numbers, but all this is beyond the scope of this article. If it sounds complicated, it’s a good thing! Why? Because now, at least, you understand that it takes more than the TSH level to evaluate the thyroid function! If for now you either don’t have access to more specific blood tests, or you haven’t found a functional medicine doctor, you can still have a few more information by having your T4 and T3 checked. If we keep it simple, when you have your thyroid functions tested, ask if they’ll evaluate only the TSH. If the answer is yes, ask if you can have your TSH, T4, T3 and iron levels measured as well. Einstein said that everything should be made as simple as possible, but not simpler, I think you would agree that just looking at TSH you’re on the simpler side.