“...my labs are normal.”
I have heard some variation of these four words since I became interested in and more focused on thyroid disorders. Now that I’m working at Modern Thyroid Clinic, I hear some variation of “my labs are normal” on a routine basis.
“I’m always cold/exhausted/have brain fog, but my doctor says my labs are normal.”
“I feel like I have low thyroid function but when I talked to my doctor about it, I was told my labs are fine.”
The following conversation occurred shortly after I officially started at Modern Thyroid Clinic and it sums up the experience most of our patients have. I was talking to a woman about my new job. When I told her I was working at a thyroid-focused practice, she told me she had hypothyroidism and was on Synthroid.
“How are you doing on your medication?”
“My doctor says my labs look good.”
“But how are you feeling?”
“I’m so tired and have no energy.”
If you’re reading this, then you must know what it feels like to go to your provider, hoping to find answers about why you’re so tired, have gained weight, and have so much brain fog you can’t remember which way is up. And then to be told... “your labs look good, you’re fine”!
I truly believe the vast majority of providers want to do what’s right for their patients. I know I did and I tried to do that with all of my patients, but when it came to managing the fatigue, brain fog, weight gain, insomnia, etc, I was completely ill-equipped. One of the reasons for this is that I just didn’t know much beyond looking at a TSH to screen for thyroid disorders. And if I did happen to look at a patient’s lab results, I did what most providers do- I looked to see if the value fell into the “out of range” section of the lab report. If the lab value was considered “normal” then everything must be fine.
Why shouldn’t a provider be able to rely on labs? For one, the correct labs aren’t being ordered. The second reason is that there is too much focus on a “normal lab range” when reviewing the results and disregarding or dismissing a patient’s symptoms because of the normal lab value.
Let’s start with what labs are typically being done, TSH ONLY!
Currently, TSH (thyroid stimulating hormone) is considered the “gold standard” for evaluating thyroid function. TSH is a hormone produced by the pituitary gland which tells the thyroid to produce it’s output hormone, thyroxine (T4). Thyroxine then converts to triiodothyronine (T3) which is responsible for metabolism of every tissue in the body.
Most providers, endocrinologists included, just test TSH. If TSH is elevated, the thyroid is not making enough T4 and the pituitary gland is working overtime to tell the thyroid to produce more T4- this is what happens in hypothyroidism. The reverse is true for hyperthyroidism- the thyroid is doing too good of a job making T4 and there is too much thyroid hormone circulating so the pituitary gland releases less TSH in an effort to slow production. TSH tells us what the pituitary gland is doing, and from that, medical providers draw a conclusion about what’s happening in the thyroid. The problem with that is there is so much going on at a cellular level and TSH just isn’t an accurate reflection of that.
Now that we’ve reviewed TSH, let’s talk about the other labs that need to be ordered to truly assess thyroid function.
Free T4 (FT4), Free T3 (FT3), and Reverse T3 (RT3)
If your provider does decide to check other labs besides TSH, FT4 is what is checked. Sometimes, providers order a TSH with Free T4 reflex- basically, if TSH falls outside the normal then FT4 is evaluated. If TSH is “normal”, then it’s not done.
T4 (thyroxine) is an inactive thyroid hormone produced by the thyroid- ~80% of the hormone produced is T4 and 20% T3. Consider T4 the “holding place” for conversion into T3.
T3 (triiodothyronine) is the active thyroid hormone- it is 300 times more biologically active than T4 and is what we can attribute most of the function of the thyroid gland to.
But why not rely on free T4? If the levels are good, then you can assume that free T3 levels will also be adequate, right? Not necessarily. That’s assuming conversion from T4 to T3 (by way of losing an iodine molecule) is actually occuring.
Let’s look at conversion this way- T4 and T3 are important for thyroid function, but T3 is where most of the power lies. T3 is the gasoline to T4’s crude oil. If you’ve listened to McCall speak, this one of her favorite analogies. T4 is your crude oil- you can’t put crude oil in your car, it won’t run (or it might, but you’re really going to mess up your car). Crude oil has to be converted to gasoline. You can put gasoline in your car, gasoline is what makes the car run efficiently. We need adequate levels of T4, as that’s what we get our supply of T3 from. Our bodies need adequate levels of T3 in order to function properly.
T4 can also convert into another hormone, called reverse T3 (RT3). Reverse T3 is an inhibitory hormone. It mimics free T3 in that it binds to the same receptor site but is unable to “activate”. It is one of our built in protective mechanisms. In times of stress, reverse T3 increases. Why? It’s telling our bodies to slow down, to go into hibernation mode as a way to protect us from whatever hardship we’re facing. This is supposed to be a short term occurrence as at some point, the stress should decrease or resolve. Unfortunately, we are often faced with an endless stream of stressors, with no end in sight. As a result, reverse T3 remains consistently elevated. When reverse T3 is elevated, a person can still be highly symptomatic even if the TSH, free T4, and free T3 are in the optimal range. Knowing reverse T3 levels are important for initiating thyroid treatment and adjusting medications.
As you can see, understanding conversion is key to adequately managing hypothyroidism. The most commonly prescribed medication to treat hypothyroidism is medication containing T4 only. This decision is based on the assumption that every person’s conversion process is working properly. If you’re not properly converting T4 to T3 and you’re put on Synthroid, Levothyroxine, etc, you most likely will NOT notice any improvement in symptoms. If anything, you’re going to feel worse, because now, you have so much extra T4 in your system, and most of it is going to reverse T3.
The most frustrating part of this? You follow-up with your doctor and report you’re feeling worse than before. The response you get? “Well, it must not be thyroid (sometimes with an added on “like I thought”), because if it was your thyroid, you would be feeling much better on it.”
Finally, last but not least, testing thyroid antibodies to evaluate Hashimoto's. Those antibodies are thyroid peroxidase (TPO) and thyroglobulin (TgAB). For patients with Graves disease, thyroid stimulating immunoglobulin (TSI) is the antibody to test for if patients exhibit any symptoms of hyperthyroidism. Hashimoto’s is an autoimmune condition in which the body essentially attacks the thyroid gland. The leading cause of hypothyroidism? You got it...Hashimoto’s! Yet, thyroid antibodies aren’t always checked, or if they are, it’s checked much later on in the process. The reason for wanting to know if a patient is positive for antibodies is that early detection and intervention can slow or even halt the process of Hashimoto’s. There is so much to discuss regarding Graves and Hashimoto’s that it will be covered in a future blog post.
These labs, TSH, free T4 and T3, reverse T3, and thyroid antibodies should always be ordered when undergoing an evaluation for hypothyroidism as it allows for a full picture of current thyroid status. Trying to manage hypothyroidism based off of TSH alone does not take into account what happens at the cellular level, but also results in ongoing symptoms and frustration. Knowing what is happening at every level of thyroid function is what allows me as provider to better address the overall well being and functionality of my patients. As we like to say at Modern Thyroid Clinic- “There is no reason to still have thyroid symptoms.”