Hypothyroidism: More than just TSH

The thyroid controls our metabolism - it's like the body's thermostat. If it's under-functioning (think: slow metabolism), we can feel tired, cold, experience weight gain, low mood, constipation, hair loss, and/or dry skin. If this sounds familiar, you’re not alone!

It is estimated that thyroid disorders affect 1 in 3 Canadians, but 50% of cases go undiagnosed. In addition, women are seven times more likely to experience a thyroid disorder than men. In this article, I’m going to focus on lab testing and understanding how thyroid hormones impact the body.

Why are thyroid disorders under-diagnosed? There are three main issues.

1. Traditional lab testing only looks at what is called the TSH (see below for explanation of what that is...). The TSH provides only a fraction of the bigger thyroid picture, and often misses thyroid dysfunction when tested in isolation.

2. The lab reference range for “normal” TSH has been long-disputed, with research supporting that a normal range should be narrowed from 0.45-4.50, to 1.0-2.5. A tighter reference range would result in more diagnoses, or in my opinion, at least flagging people who are trending toward hypothyroidism before they reach full disease.

3. The most common complaints women experience when their thyroid are fatigue and weight gain. Unfortunately, many patients aren’t heard when they bring these symptoms up with their family doctors, and they are just told to get more sleep and go on a diet.

How should we test and treat thyroid issues?

1. TSH measures a signal that we send from the brain to the thyroid gland. A high TSH means the brain is screaming at the thyroid, “Make more thyroid hormones!” because it is underperforming (called hypothyroidism).

Think of this like a parent asking their kid to do their homework. If the kid isn’t listening, the parent yells more loudly. If the kid is working well already, the parent barely has to whisper to ask that they get their work done.

- High TSH = low thyroid function

- “Normal” range = 0.32 – 4.00 mIU/L

- Ideal range = 1.00-2.5m mIU/L

Treatment: See treatment options below, depending on the cause of high TSH.

2. Free T4 (occasionally tested) is a measure of what your thyroid gland is actually producing. Think of this as the homework that is actually being done. Usually, the parent knows if they need to motivate their kid more/less, but the parent doesn't realize that the kid's homework is sub-par. This lab test allows us to see if you’re experiencing a production issue from the thyroid itself.

- Low T4 = low production of thyroid hormone

- Normal range: 9-19 pmol/L

- Ideal range: 14-16 pmol/L          

Treatment: use iodized salt for cooking at home, increase Tyrosine in the diet, and herbs to boost thyroid function.

3. Free T3 (not typically tested) is our active thyroid hormone, which has been converted from T4 in the body. This one is tricky because it’s less stable than free T4, so it needs to be tested with T4. Think of this as the mark the child’s homework receives from their teacher. Since it’s a measure of conversion from T4 to T3, it allows us to see if hypothyroid symptoms are caused by an issue with converting T4 to active T3.

- Low T3 = slow metabolism

- “Normal” range = 2.6 – 5.8 pmol/L

- Ideal range: 4.0-5.5 pmol/L

Treatment: selenium and zinc to improve the conversion of T4 to T3.

4. Reverse T3 (rarely tested) is our inactive thyroid hormone. When the body is stressed, it converts some T4 into reverse T3 instead of active T3. This is your body’s way of slowing down your metabolism to give you a better chance of survival during a stressful time, like a war or famine. Think of it like a mini-hibernation caused by stress.

- High rT3 = slow metabolism

- Normal range = 8-25 ng/dL

- Ideal range: <13 ng/dL

Treatment: reduce stress, incorporate herbs to regulate cortisol (stress hormone).

5. Autoimmune markers can also be tested to see if the thyroid is slow because it is being attacked by your immune system. This is called Hashimoto’s hypothyroidism, and it impacts the way we approach thyroid treatment and assess progress over time

Treatment: address the immune system with gut-support and dietary changes.

6. Lastly, in people who have already been diagnosed with hypothyroidism and are taking medication (called Levothyroxine), in-depth testing can also be helpful to optimize the efficacy of your medication in the body.

Overall, the thyroid cascade is a perfect example as to why we often need more in-depth lab testing to understand the bigger picture of what is happening in the body. When we understand the why we can target and treat the underlying cause, and often catch things at the start of decline before they progress to full disease.

If you're feeling sluggish, have difficulty losing weight, constipation, dryness, and/or fatigue, book an appointment with your Naturopathic Doctor to assess your full thyroid panel, and treat the root cause of metabolic dysfunction.