Why testing your TSH alone isn’t telling you much about your thyroid

If you or your doctor suspect that you have a thyroid imbalance, the standard course of action is to run a TSH test. TSH stands for “thyroid stimulating hormone” and it’s made in the pituitary gland. Yes, that’s right, TSH is not made by the thyroid, it’s made by a gland in the brain. Now you might be wondering- why are we looking at a hormone made in the brain to assess the thyroid? That’s a great question!

TSH is an indirect way to look at your thyroid. I like to describe TSH as a doorbell. It’s a signal from the brain (ding-dong!) to the thyroid to make thyroid hormones (T4 and T3- which we’ll talk about in a minute). The assumption is that when your thyroid hormone levels drop, TSH will rise to stimulate the thyroid. The problem is that a TSH test on its own doesn’t tell us much. Is the thyroid responding properly to TSH and making T4 and T3?

T4 is the main hormone produced by the thyroid gland so it is a much more direct way to see how your actual thyroid is doing. If T4 levels are low, it means your thyroid is sluggish and isn’t making enough thyroid hormone. Keep in mind that T4 is a weak and mostly inactive hormone. Its main goal is to be converted into T3 which is the active thyroid hormone which gives you energy, helps you maintain a healthy weight, balances your mood and regulates body temperature. In my opinion, T3 is the MOST IMPORTANT thyroid hormone to test because it’s the one that is actually doing all the work and helping you feel good. TSH is just a signal. It has no direct impact on your weight, energy or mood.

Woman thyroid gland control isolated on white backgroundWoman thyroid gland control isolated on white backgroundLow T3 levels are incredible common and I can’t tell you how many women I see in my practice who have a low T3 hormone but their TSH is perfectly normal. So, if your doctor is only checking your TSH levels, they could tell you that everything looks great when in reality you may have low T4 and T3 hormone levels causing symptoms of hypothyroidism.Woman thyroid gland control isolated on white background

For a full picture of how your thyroid is working, I recommend getting a full thyroid panel that includes the following tests:

  • TSH
  • Free T4
  • Free T3
  • TPO (thyroid peroxidase) antibodies
  • TG (thyroglobulin) antibodies
  • Reverse T3

To learn more about each of these tests and the optimal ranges to look for, check out my 5 Essential Thyroid Tests for Women.

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5 Essential Thyroid Tests for Women

If you are experiencing some of the following symptoms, it may be worth having your thyroid tested to rule out thyroid hormone imbalances:

  • Very slow or very fast heart rate
  • Weight gain or difficulty losing weight (or rapid weight loss)
  • Change in menstrual cycles (irregular periods, heavy periods)
  • Always feeling very cold or overly hot (or going from one extreme to the next)
  • Fatigue
  • Hair loss
  • Elevated LDL cholesterol level
  • Depression

5 Essential Thyroid Tests to ask for:

  1. TSH (thyroid stimulating hormone)
  2. Free T4
  3. Free T3
  4. TPO-antibodies & TG-antibodies
  5. Reverse T3

Understanding Your Test Results

1. TSH is short for thyroid-stimulating hormone, a hormone made by the pituitary gland (located in the brain) which tells the thyroid what to do. Think of it as the knock on the door. If the thyroid is not doing it’s job, the pituitary will knock more loudly (elevated TSH) whereas if the thyroid is working optimally, the knock will be very light (lower TSH). As you can see, TSH is not made in the thyroid meaning it’s an indirect way of looking at thyroid function.

High levels of TSH may indicate hypothyroidism (i.e. underactive thyroid), a pituitary gland tumor, or inadequate thyroid hormone medication in the treatment of a preexisting condition. Low levels of TSH may indicate hyperthyroidism (i.e. overactive thyroid), damage to the pituitary gland, too much thyroid medication in the treatment of a preexisting condition, or pregnancy in the first trimester.

  • Normal Range: 0.4-5 mIU/L
  • Optimal Range: 0.4 -2.5 mIU/L
  • Hypothyroidism = TSH > 5 mIU/L
  • Hyperthyroidism = TSH < 0.4 mIU/L

2. Free T4: T4 is the main hormone produced by the thyroid so it’s the most direct way at looking at actual thyroid gland function. Keep in mind that T4 is a very weak, mostly inactive hormone that’s main purpose is to be converted into T3 (see below).

  • Normal Range: 9-22 pm/L
  • Optimal Range: 14-18 pm/L
  • Hypothyroidism = < 9 pm/L
  • Hyperthyroidism =  > 20 pm/L

3. Free T3: is made from T4 throughout the body but mostly in the liver. T3 is the most active form of thyroid hormone and is responsible for giving us energy, revving up our metabolism, keeping us warm and with hair on our head. It’s vital to look at T3 hormone levels in order to gauge if there is thyroid dysfunction because you can have normal TSH and T4 levels but if you aren’t converting well to T3 you can still have symptoms of thyroid imbalance.

  • Normal Range: 3.4-5.9 mIU/L
  • Optimal Range: 4.5-5.5 mIU/L
  • Hypothyroidism =  <3.4
  • Hyperthyroidism =  > 6

4. Thyroid Antibodies (TPO and TG): Thyroid peroxidase (TPO), an enzyme found in the thyroid gland, plays a key role in the production of thyroid hormones. A TPO test detects antibodies against TPO in the blood, the presence of which suggests that the cause of thyroid disease is an autoimmune disorder (e.g. Hashimoto’s or Grave’s disease).

  • Normal Range: < 35 kIU/L
  • Auto-immune disease (e.g. Hashimoto’s or Graves’s) > 35 kIU/L

5. Reverse T3: is essentially a “dud” hormone that is made when the body is under stress. A small percentage of our T4 hormone is always converted to reverse T3 in order to prevent the body from being overstimulated by T3. However, in certain conditions, especially with higher stress and cortisol hormone levels, the body can convert too much T4 into reverse T3 which essentially blocks other thyroid hormones from doing their job.

  • Normal Range = < 9-24 ng/dL
  • Optimal Range = less than 18 ng/dL

These tests are all done through a simple blood test which your MD can request. Naturopathic Doctors are also able to run these tests which will cost approximately $100.

Getting to Know Your Thyroid

Written by: Sarah Vadeboncoeur & Anita Kushwaha

What is your thyroid?

Your thyroid is a small, butterfly-shaped gland situated at the base of the front of your neck, just below your Adam’s apple.

thyroidgland

What does your thyroid do?

The thyroid gland uses iodine from the foods you eat to make two main hormones:

  • Triiodothyronine (T3)
  • Thyroxine (T4)

These hormones produced by the thyroid gland — T3 and T4 — have a great impact on your health, affecting all aspects of your metabolism.

The thyroid’s hormones regulate vital body functions. For instance, they maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate, and help regulate the production of proteins.

If your thyroid isn’t functioning optimally, it may affect:

  • Heart rate
  • Nervous system
  • Body weight and metabolism
  • Muscle strength
  • Menstrual cycles
  • Body temperature
  • Cholesterol levels

What is hypothyroidism?

Hypothyroidism (i.e. underactive thyroid) is a condition in which your thyroid gland doesn’t produce enough of the above mentioned hormones. When this occurs, bodily functions slow down.

Hypothyroidism may either be genetic or develop in the course of life. There can be many different causes for an underactive thyroid. For example, one reason might be a lack of iodine. Getting enough iodine through your diet is therefore important for normal thyroid function. Similarly, a condition called Hashimoto’s thyroiditis –  an auto-immune condition that causes chronic inflammation of the thyroid – can also lead to underactivity.

What are the symptoms of hypothyroidism?

Hypothyroidism symptoms may include:

  • Fatigue, tiredness
  • Slowed heart rate and metabolism
  • Weight gain
  • Muscle weakness, aches, tenderness and stiffness
  • Constipation, digestive upset
  • Elevated blood cholesterol level
  • Heavy or irregular menstruation
  • Cold sensitivity
  • Hair loss or dry/brittle hair
  • Dry skin
  • Joint pain, stiffness or swelling
  • Depression
  • Impaired memory and concentration
  • Loss of sexual desire

Concerned about your thyroid function? Contact Dr. Sarah to inquire about getting your thyroid levels tested.

 References:

  1. Mayo Clinic: http://www.mayoclinic.org/diseases-conditions/hypothyroidism/home/ovc-20155291
  2. PubMed Health: https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072572/
  3. EndocrineWeb: https://www.endocrineweb.com/conditions/thyroid/hypothyroidism-too-little-thyroid-hormone