How to Interpret Thyroid Labs

Thyroid lab interpretation can be hard to figure out, but it is definitely possible! In my humble opinion, it is not just science, but also an art that comes with more and more experience and helps to figure out if your thyroid gland is slacking and why.

How to Interpret Thyroid Lab Results

As a rule, I check all thyroid hormone with all the markers. It is necessary to check the complete thyroid panel to understand better where the deficiencies can be hidden. Ask your healthcare provider to check TSH, Total T4 and T3, Free T4 and T3, Reverse T3, and at minimum Thyroid Peroxidase (TPO) and Thyroglobulin Antibodies. I still remember the time when it was hard for me to remember how to pronounce the names of the most common antibodies I have just listed above. Now, it is a piece of cake for me:)

Below, you see the complete thyroid panel that at the first glance looks very optimal.

TSH 1.32 (optimal 1.0 – 2.0).

Total T4 6.1 (lab range 4.5 – 12.0). Thyroxine 6.1 is only 1.6 points over the minimum lab normal of 4.5. It is definitely not optimal. Being mid-range around 8.0 would make it roughly optimal. It means that the total pool of Total T4 is quite low and made downstream T3 may be in the lower range too. One of the reasons of not having enough Total T4 would be the lack of nutrients such as zinc, iron, B vitamins, selenium, Vitamin D, and iodine – the building blocks for the thyroid hormone.

Total T3 103 is as expected on the lower normal range just 30 points above the lowest normal per lab range. To be optimal, the level over 120 would make more sense.

Free T4 1.09 (0.82 – 1.77) is almost in the optimal range of 1.1 – 1.5. The fact that it is not very high may mean 2 things: 1. There is not enough Total T4 to make more Free T4; 2. There is no conversion issue where Free T4 is pooling and not converting into Free T3 optimally.

Free T3 3.1 (2.0 – 4.4). The median would be 3.2 – optimal middle where most patients would be at the optimal range per their thyroid lab markers.

BUT … Let’s look at Reverse T3 and calculate Free T3/Reverse T3 ratio:

FT3/RT3 = 3.1 pg/mL : 18.1 ng/dL = RT3 Ratio: 17.1%

Complete Thyroid Laboratory Analysis

Excess Reverse T3 has emerged lately as the laboratory analysis of Reverse T3 does not cost an arm and a leg anymore. It appears more and more on my radar as more and more people come being treated with T4-only medication such as levothyroxine (Synthroid) and with time they lose the ability to convert synthetic T4 into T3 and instead T4 gets converted into Reverse T3. It can be caused by chronic adrenal dysfunction and low or high cortisol, as well as iron deficiency and lack of necessary nutrients and vitamins. Low Vitamin B12, chronic stress, and strenuous workouts such as boot camps or CrossFit can cause the increased conversion of T4 to Reverse T3. Reverse T3 >15.0 makes me concerned about Thyroid resistance, but to see the whole picture, the ratio of Free T3/Reverse T3 has to be calculated.

With the Free T3/RT3 ratio, healthy ratios will be 20% or higher.

The good news for this person is that Thyroid Peroxidase Antibodies and Thyroglobulin Antibodies are within the normal range. Nevertheless:

“About 5 % of patients with a diagnosis of Hashimoto’s thyroiditis based on clinical grounds or by ultrasound appearance have no measurable thyroid antibodies.”

Patients with Hashimoto’s thyroiditis and negative thyroid antibodies have a milder form of the disease

According to another source, the estimate of the number of patients suffering from Hashimoto’s disease with no evidence of antibodies is even more generous:

“There is a small subset of the population, no more than 10%  with the clinically evident disease, that are serum antibody-negative.”

Hashimoto Thyroiditis

That is why in the absence of thyroid antibodies, I still recommend a basic non-invasive ultrasound that helps to see if there are any nodules in the thyroid gland and if the thyroid tissue is heterogenous (different structure and composition) which would be consistent with a possibility of Hashimoto’s or homogenous which would mean that thyroid tissue is of uniform structure or composition.

Let’s look at one more example! What can you tell about these labs?

Basic Thyroid Labs

Thyroid Stimulating Hormone (TSH) 1.44 (1.0 – 2.0 optimal); Free T4 1.3 is in the optimal range too, but Free T3 is just 2.7! Labs are not everything, so it is ALWAYS necessary to find out if and how many hypothyroid symptoms the person is experiencing. If there are a lot of hypothyroid symptoms and Free T3 is lower than 3.2-3.5, I would consider addressing the underlying vitamin and mineral deficiencies, as well as a trial of thyroid hormone. It is more and more often that Thyroid Stimulating Hormone is not rising as it should in order to stimulate the thyroid gland to make more thyroid hormone. Instead, TSH gets into the optimal range of 1.0 – 2.0 and Free T3 and Free T4 slowly decline and a person may experience hypothyroid symptoms that get worse and worse. The more time passes that the thyroid function is not reestablished, the more hypothyroid symptoms accumulate. Moreover, the more difficult to treat the dysfunction that follows.

Thyroxine (Total T4) 7.6 – close to optimal 7.0 – 9.0; but Total T3 is just 80 with the lab range of 80-200! Let’s make a guess whether this person has hypothyroid symptoms or not?

So, what are the consequences of not treating hypothyroidism and optimizing the thyroid function?

For example, if you are genetically predisposed to diabetes Type 2, being hypothyroid for a long time, at first the person may develop blood sugar dysregulation, i.e. high and low blood sugars, even on lower-carb diet. After some time, the person may develop pre-diabetes which left untreated will turn into Type 2 Diabetes requiring medications and later insulin injections. The issue with that is that the underlying cause – low thyroid hormone or thyroid hormone resistance – stay unaddressed and the person gets medication for every type of symptom.

Typical Hypothyroid Symptoms Treated with Medication:

“The Pill for Every Ill”

  1. High Cholesterol – Statin drug.
  2. Depression – Anti-depressant.
  3. Anxiety – Anti-anxiety medication.
  4. Pre-diabetes and diabetes – Metformin, and other medications to decrease blood sugar.
  5. Constipation – Maalox, and other laxatives.
  6. Heavier than normal or irregular menstrual periods – Oral Contraceptive Pills.
  7. ADHD, inability to focus – Adderall, etc.
  8. And the list goes on…

I hope that now you have a better understanding of what thyroid labwork means and how to attempt to interpret it. This would help you to get a different point of view if your healthcare practitioner tells you that your lab work is “normal” while you are having a lot of hypothyroid symptoms and struggling every day to get going and have enough energy to get through the day! If you ever find yourself in this situation, please, get a second opinion from a functional healthcare provider – who is listed on The Institute for Functional Medicine website

Now, share your experience with your thyroid lab interpretation and what helped you get on the right track when it comes to finding a healthcare provider who would listen!