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What Are Optimal Thyroid Levels?

What Are Optimal Thyroid Levels?

There is a serious misconception in the medical community regarding thyroid testing and treatment practices. Many medical professionals including endocrinologists incorrectly believe that the standard thyroid testing protocol provides an accurate view of thyroid function. In reality, the current practice of relying solely on TSH is not reliable. Worse still, doctors frequently use inappropriate test ranges to inform decisions for treatment. Attaining an accurate assessment of the thyroid and using that information to provide optimal treatment requires thorough testing and a better understanding of thyroid test ranges. 

The Problem with Current Testing Practices

Most medical institutions use thyroid stimulating hormone or TSH as the sole metric for measuring thyroid function. TSH does play a role an important role in thyroid function but using this value as the only reference is irresponsible and discounts the many other factors involved. 

TSH is a hormone produced by the pituitary gland that tells the thyroid when more thyroid hormone is needed. Many doctors posit that this information is all that is required to get an accurate view of thyroid health. However, TSH values only describe how well the pituitary is communicating with the thyroid while having minimal bearing on the production, values, activity, or transport of thyroid hormones. Because TSH only gives a partial picture, properly assessing the thyroid requires that additional tests be done.

Learn more about the inadequacy of the TSH test here.

What Tests Are Needed to Assess the Thyroid?

Getting an accurate image of thyroid activity and wellness requires that, in addition to TSH, several thyroid-related substances be tested. Free T4 (thyroxine), Free T3 (triiodothyronine), Reverse T3 (reverse triiodothyronine), thyroid antibodies, and sex hormone-binding globulin (SHBG) are the minimum tests required to get a truly accurate view of individual thyroid function. 

Get a FREE downloadable lab slip with a complete thyroid panel here.

Thyroid Stimulating Hormone (TSH)

Irregular levels of TSH may be indicative of several different forms of dysfunction. Elevated TSH may suggest poor thyroid hormone production. Reduced TSH values may indicate increased thyroid hormone production or that the dose of an individual’s thyroid medication is too high or it is simply being artificially lowered by thyroid replacement hormone medication.

Free T4

T4 is the inactive form of thyroid hormone. Knowing how much T4 is available to be converted into T3 and how much is circulating in the bloodstream is valuable for assessing thyroid activity. Elevated T4 may suggest increased thyroid activity while reduced levels often indicate a decline. 

Free T3 and Reverse T3

T3 is the active form of thyroid hormone and is responsible for accelerating cellular activity. Reverse T3 is the mirrored version of T3 and limits the effects of T3, which effectively slows bodily function. Perhaps the best single indicator of thyroid function is the ratio between circulating T3 and Reverse T3. High T3 suggests hyperthyroidism. Conversely, low T3 may indicate poor conversion of T4 to T3 resulting in hypothyroidism. Increased values of Reverse T3 suggests over conversion of T4 to Reverse T3, which contributes to hypothyroidism. 

Learn more about the T3/RT3 ratio and get access to the ratio calculator here.

Thyroid Antibodies

Thyroid antibodies such as thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) are agents produced by the immune system that target specific parts of the thyroid gland. Increased values of these substances may indicate autoimmune thyroid disease such as Hashimoto’s thyroiditis or Graves’ disease. Both of which can result in severe thyroidal malfunction. 

Sex Hormone-Binding Globulin (SHBG)

SHBG is an important factor in the transport of various hormones including the sex hormones testosterone and estrogen. It also acts as a carrier for thyroid hormone. Assessing SHBG levels and activity can provide information regarding the accessibility and delivery of thyroid hormone throughout the body. Reduced levels of SHBG may suggest poor hormone transport that contributes to hypothyroidism. 

The Difference Between “Normal” and Optimal Test Ranges

The current standard of thyroid testing is composed of a large range for what is considered normal. Because of the broad parameters, thyroid patients may display results in any of the above substances at many different levels while still being considered healthy. For example, a TSH between 0.5 and 3.0 is considered “normal” by most practitioners even though a shift of just 0.5 can have a dramatic impact on thyroid function, symptom occurrence, and overall feelings of wellness.

Ideally, each thyroid patient would be treated in a manner that has them reach their optimal level rather than an overly expanded “normal” range. Optimal levels are those that make patients feel their best. Unfortunately, reliance on a standardized and bloated testing range leaves little opportunity for patients to land anywhere near their optimal values. Achieving optimal values requires that doctors work with their patients, test all relevant factors, monitor changes in symptoms, and listen to patient reports and concerns. Reaching your optimal levels may be challenging but with comprehension and persistence it is possible. 

Where to Start Thyroid Optimization

Optimal values are different for every thyroid patient. Typically, doctors work with patients to identify problem areas and optimize errant values. The broad ranges used by the medical community at large make it difficult to narrow down what require optimization. For this reason, many thyroid advocates, practitioners, and experts utilize the updated ranges below as they tend to be much closer to individually optimized levels. However, it is important to keep in mind that optimal levels are always dependent on the individual patient.

These metrics are a good point of reference to use when trying to identify your optimal values.   

  • TSH between 1-2 UIU/ML or less
  • Free T4 greater than 1.1 NG/DL
  • Free T3 greater than 3.2 PG/ML
  • Reverse T3 at a ratio less than 10:1 / RT3:Free T3
  • Thyroid Antibodies less than 4 IU/ML or in the negative

The hope is that by using these more stringent reference ranges, patients will be more quickly brought to a point closer to their optimal level. From there, finer adjustments to treatment can be made to get patients to the values that make them feel best. Armed with this information, you can now work with your doctor more effectively find your optimal values and implement the appropriate changes to reach them. 


1. Kent Holtorf, MD. “Diagnosis of Hypothyroidism: Are we getting what we want from TSH testing?”
2. Kent Holtorf, MD. “Understanding Local Control of Thyroid Hormones: (Deiodinases Function and Activity).”
3. Amy Myers, MD. “What Your Thyroid Lab Results Really Mean.” Amy Myers, MD.

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Jan Mumford
Jan Mumford

Don’t the lab ranges vary from place to place? Especially countries other than the US? It would be helpful if you included the typical ranges in the article. I’m guessing your numbers are mid-range and higher for the frees?

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