Hypothyroidism: More than TSH

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

The CBC reported 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 big 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 most cutting edge research supporting that a normal range should be narrowed from 0. ** to 0.5 – 3.0. A tighter reference range would result in more diagnoses, or in my opinion, at least capturing 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 up in their appointments, and they are just told to get more sleep and go on a diet.

What is included in a full thyroid panel?

1. TSH (the typical test) is a measure of how loudly your pituitary gland is screaming at your thyroid gland. The higher the number, the louder the screaming, indicating that your thyroid is under functioning. I think of this like a parent asking their child to do their homework. If the kid isn’t listening, the parent yells more loudly. If the kid is working on their own, 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

2. Free T4 (not typically 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 understands if they need to motivate the child more/less, but sometimes the homework is incomplete without the parent realizing it. 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

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 run together 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 it symptoms are due to a conversion issue.

  • Low T3 = low metabolism
  • “Normal” range = 2.6 – 5.8 pmol/L
  • Ideal range: 4.5-5.5 pmol/L

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 war or a famine. The trouble is, we don’t need rT3 to survive in Canada, and this is often a huge piece of the puzzle that is overlooked.

  • High rT3 = low metabolism
  • Normal range = 8 – 25 ng/dL
  • Ideal range <13 (some say <10) ng/dL

5. Autoimmune markers (anti TPO, anti TG) can also be tested to see if the thyroid gland is being attacked by your immune system. This is called Hashimoto’s hypothyroidism, and it impacts the way we address your thyroid treatment and assess progress over time.

The bottom line

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.

Lastly, in some people who have already been diagnosed with hypothyroidism and are taking medication, full panel testing can also be helpful to optimize the efficacy of your medication in the body.

Book your appointment to address your thyroid heath.