Do you really understand your Thyroid Labs?

Do you really understand your thyroid labs, and why should you care? It’s important to know what is happening with your labs because knowing is power. Getting to the root cause of your problems can make a big difference in your health.

When you have lab work performed, your results are compared to normal ranges.

Most people think these normal ranges are set as a standard across all labs, but they’re not. Labs follow clinical and lab standard institute guidelines that the FDA recognizes. These guidelines suggest that every lab create their own lab normal from patients that come into their labs for testing. They suggest that the lab compile results from as little as 20 patients up to 120 patients. You must wonder if these are normal healthy individuals who are getting tested? In addition, they recommend that each lab’s normal ranges be compiled from 95% of the tested individuals. This leaves only 5% that is outside the range – 2.5% higher than 95% and 2.5% lower than the 95% middle range.


In functional medicine, we use ranges from truly normal, healthy individuals who never had problems–those with optimal health. Many doctors never look at your lab values but instead look at a place where the lab signifies that it is out of the lab’s normal range. This can be a problem because you never really know what optimum levels are.

TSH (Thyroid Stimulating Hormone) is a hormone produced by the pituitary gland.

TSH tells the thyroid to speed up and produce more hormones. This is considered a negative feedback loop. For example, when the pituitary increases TSH, the thyroid increases its production of thyroid hormone. The pituitary then senses the thyroid hormone levels increase and then reduces its output of TSH.

The typical lab range for the TSH value is 0.5-5.5 mU/L, which is too large of a range. If you get a TSH lab result of 3.5 and up, by functional medicine standards, this means that you may have hypothyroid problems, but conventional medicine considers this normal.


On the other hand, the functional range is 0.3-2.5 mU/L. This is a good lab value to have. Normally, TSH should be well balanced with T3 and T4, according to functional medicine standards.

In hypothyroidism, there is a decrease in T3 and T4 levels while there is an increased level of TSH in the body.

TSH is produced by the pituitary in a response to get your thyroid gland to produce more hormone. The increase in TSH levels is relatively gradual as it keeps on “telling” the thyroid to produce more hormone.


Some of the signs and symptoms of hypothyroidism include obesity, swelling, being cold, constipation, thinning hair, slow heartbeat, loss of the outside 1/3 of your eyebrows, and edema in the eyes, especially when you wake up in the morning. And there are many more symptoms. Hashimoto’s disease, an autoimmune disease, is considered one of the leading causes of hypothyroidism. If you have this problem, your immune system is attacking your thyroid gland. If this goes on long enough, your thyroid gland may be completely destroyed, rendering its hormone production absent.

In hyperthyroidism, there is a decrease in TSH and an increase in T3 and T4 levels.

In this case, the body produces too much thyroid hormone causing the TSH levels to decrease. Values may go from 2.5 down to 0.2 and sometimes 0. If you have this dysfunction, you are likely to have Graves’ disease, which can also be accompanied by ophthalmopathy/ophthalmology (bulging eyes). Once you have it, it won’t go away even if your thyroid hormone levels start to get better. There are surgical means that can help minimize this condition, but it’s a tough one to have even with this intervention.


T4 is a tyrosine-based amino acid hormone.

It makes up about 93% of your thyroid hormone. It’s inactive and gets converted in the liver (60%) and your gut (20%). The remainder is eventually processed in the peripheral tissues. This is converted into T3 which is the active thyroid hormone.

It is also made up of iodine placed in each or all of the corners of the molecule depending if its T4, T3 or rT3 (reverse T3). This arrangement makes it fit into the receptor site if it is in the active T3 or rT3 form. T4 is not active and doesn’t fit into the receptor on the cell.


This inactivity happens for a good reason. Can you imagine all the thyroid hormones being active at the same time? Certain cells close to the thyroid would always be in overdrive while others far away from the gland may not get any at all.

In addition, T4, the inactive hormone, lasts longer in the system than T3, which is the active form. T4 (protein bound) is attached to thyroxine binding globulin (also known as TBG) which transports the thyroid hormones in circulation.

T4 free is not bound to protein and has a great propensity to be converted to T3, the active thyroid hormone. The typical lab range for T4 (protein bound) is 4.5 – 12.0, while T4f (free) is 0.8 – 1.70. On the other hand, the functional range for T4 (protein bound) is 6.0 – 12.0, while T4f (free) is 1.0 – 1.50. Most doctors only check TSH and T4, and if you’re lucky, they may check T3, but it’s quite rare.

T3 is the thyroid hormone that does all the work.

T3 is also produced at the thyroid gland (7%), though its mainly produced through conversion. T4 is transformed into T3 by an enzyme called 5’ deiodinase. This is an enzyme that depends on the mineral selenium.

T3 is bound to protein which is regarded as a transport mechanism. It’s not an active hormone at that point in time until it becomes free. T3 free is what we usually evaluate. If you observe the following values, you will see that the typical lab ranges versus the functional lab ranges are quite different:


Typical Lab Range

  • T3 (protein bound): 71 – 180
  • T3f (free): 2.1 – 4.5
  • T3 uptake: 24 – 39

Functional Range

  • T3 (protein bound): 100 – 180
  • T3f (free): 3.0 – 4.5
  • T3 uptake: 27 – 37

There are various differences between T3 and T4.

For these values, “secretion” is the difference in how much hormone is actually made. The “source” is the location where the hormone is produced. “Half-life” is the amount of time it takes for the quantity to reduce to half of its initial value. “Potency” is how much the hormone is effective in doing what it’s supposed to do.


  • Secretion: 18-30 micrograms/day
  • Source: 20-25% by the thyroid; 75-80% by conversion (in the gut and the peripheral tissue)
  • Half-life: 1 day (active hormone is used up pretty quickly)
  • Potency: 3-4 times more potent than T4


  • Secretion: 80 micrograms/day
  • Source: by thyroid only
  • Half-life: 7 days (the inactive hormone stays around for quite some time before)
  • Potency: potent


T3 uptake is done to see how much thyroxine binding globulin (TBG) is available.

TBG is one type of protein that transports most of the T4 and T3 in your blood. T3RU is a lab test that measures the level of proteins that carry thyroid hormone in the blood. This is typically tested if you have signs and symptoms of hyperthyroid, hypothyroid or liver problems.

RT3 (reverse T3) is another thyroid hormone made from T4.

It looks a lot like T3, but it’s a little bit different as far as function is concerned. Approximately 60% of T4 is converted to T3. On the other hand, 20% is reverted into the inactive form of your thyroid hormone. This is called the reverse T3 (rT3) and this will attach itself to T3 receptors.  Because of this, it will block T3 from stimulating the cell, creating hypothyroid issues.

It’s important that we have enough T3 and not so much RT3. RT3 will bind to those receptor sites, creating a problem with the cell not getting enough thyroid stimulation and therefore decreasing the cell’s metabolism.


Typical lab range for reverse T3 is 11-23. The functional range is also 11-23. Reverse T3 may be both good and bad even if it is inactive by nature. The problem is that most doctors do not check for these RT3 values.

Too little or too much cortisol that the adrenals produce in response to stress will increase the circulating amounts of your reverse T3. It slows down the metabolism so you can better deal with adrenalin’s actions.

Cortisol production, because of stress, will also blunt the function of TSH, prevent conversion, and increase rT3. As a result, thyroid hormone levels drop. The following are some things that can cause high levels of RT3:

  • Immune system issues
  • Excess free radical damage
  • High adrenaline
  • Aging
  • Fasting
  • Prolonged illness
  • Drugs
  • Stress
  • Low iron and B12
  • Lyme Disease
  • Diabetes

To better assess reverse T3, you may refer to the following ratio:

  • FT3/RT3 ratio: >20
  • T3/RT3 ratio: >10



Most conventional providers do not even bother looking at autoimmunity. They just treat the low or high thyroid issues. However, it’s a very important thing in functional medicine because if you have one autoimmune disease, you’re 70-90% likely to develop an additional autoimmune disease.

The functional ranges of autoimmune labs:

  • TGAb: <0.90
  • TPOab: <13
  • TSHRab: <1.76
  • TSI: <1.3
  • TBII: <1.75

TGAb (thyroglobulin antibody). Thyroglobulin is a protein involved in thyroid hormone production.

Don’t confuse this with thyroid binding globulin which transports thyroid hormone to the blood. TGAb can be ordered for hyperthyroid evaluation and management. This is also ordered for proper diagnosis and treatment of tumors and cancer.


TPOab (thyroid peroxidase antibody). Thyroid Peroxidase is an enzyme that helps activate iodine in the making of your thyroid hormone.

It also helps connect tyrosine together for making the thyroid hormone. This test is used to determine if the person has Graves’ or Hashimoto’s disease.


TSHRab (thyroid stimulating receptor antibody) is divided into two subtypes.

There are two types of antibodies that attach to proteins in the thyroid to which TSH normally binds. This can be seen in Hashimoto’s and Graves’ disease.


TSI (thyroid stimulating immunoglobulin).

TSI is seen in Graves’ disease. One big problem is when this is positive coupled with a negative TPO, the risk of Graves’ ophthalmopathy increases (bulging eyes).

TBII (thyroid binding inhibitory immunoglobulin).

This is important for diagnosing Graves’ disease.

There is more to thyroid than just running a TSH and T4, like your conventional doctor would do.

You look at everything! You look at the different hormones: T3, T4, inactive T3 and T4. It is important to understand conversion from the inactive to the active hormone. You also look at autoimmune conditions. You especially want to look at reverse T3 because when it is high, you’re not binding T3 to the active hormone and then to cell receptor sites. Therefore, this could create symptoms of hypothyroidism. When you look at your thyroid lab test, you might see that everything is normal. If that is the case, you should also look at adrenal gland function, as they can actually have very, very similar symptoms as those with thyroid disease.