Between 1 and 10% of adults have some form of thyroid dysfunction. If you suspect there is a problem with your thyroid, your doctor will likely order a TSH test. Thyroid disorders such as hypothyroidism, hyperthyroidism, Hashimoto’s and Grave’s disease are usually diagnosed as a result of an abnormal TSH test. However, TSH levels are not the sole indicator of thyroid function.

What is TSH?

TSH is short for thyroid stimulating hormone. TSH tests are often used as the only tool to evaluate thyroid levels and diagnose thyroid disease. While TSH levels can be an indicator of thyroid imbalances, it’s only part of the equation. The thyroid and TSH don’t work alone to keep your thyroid function balanced.


TSH production begins with the hypothalamus. Located right above the pituitary gland in the brain, the hypothalamus triggers the pituitary gland to release TSH via a hormone called TRH (thyroid releasing hormone). The pituitary gland then gets the message to release the TSH to the thyroid. Then, the thyroid is stimulated to release its own hormones called T3 and T4. T3 and T4 travel back up to the pituitary gland, telling it to increase, slow or stop the production of TSH.


This constant conversation between the hypothalamus, pituitary, and thyroid glands is called HPT-axis. The HPT-axis is closely connected to every other hormone-producing part of the body, such as the adrenals, ovaries, and testes. 


Understanding the role TSH plays with other glands and hormones, it’s clear that a TSH test isn’t the only indicator of thyroid health.

What is a TSH test and what does it mean?​

Depending on the lab,the TSH normal range is 0.3-5.5 microunits/milliliter. Given the feedback mechanism at play with the HPT axis described above, a TSH lab test indicates whether the pituitary gland is telling the thyroid to efficiently produce T3 and T4, and whether the thyroid gland is appropriately producing T3 and T4. However, the TSH test won’t show whether the thyroid is responding properly to TSH (by making an appropropriate amount of T3 and T4) or whether conversion from T4 (the inactive form of thyroid hormone) to T3 (the active form) is occuring. Many people have normal TSH levels but still have hyperthyroid or hypothyroid symptoms.


When a thyroid blood test shows that TSH levels are within the “normal” range, a doctor will likely tell you that there is no thyroid dysfunction at all.

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Why TSH testing isn’t enough

A more comprehensive evaluation of thyroid function would be to test T3 and T4 levels along with TSH.Knowing how much T3 is present can uncover opportunities to treat a sluggish thyroid that would not be detectable with just a TSH test.

An abnormal T4 and/or T3 test would explain why so many patients experience troublesome symptoms such as fatigue, menstrual irregularities, and digestive issues, despite having a normal TSH. 

Since the thyroid is working in harmony with all the other body systems, there are additional tests that indicate thyroid dysfunction. Functional medicine doctors may run any of the following tests to address thyroid-related symptoms: 

  • TSH
  • Free T3 (and total T3)
  • Reverse T3
  • Free T4 (and total T4)
  • Thyroid antibodies (both thyroid peroxidase and thyroglobulin)
  • Cortisol
  • Urinary iodine 
  • Sex hormone (estrogen, testosterone, progesterone)
  • Thyroid support nutrients: selenium, magnesium, iron, and ferritin

Comprehensive testing is key to accurately determine your level of thyroid function. Functional medicine doctors holistically evaluate your symptoms, lifestyle, nutrition, and test results to heal and preserve your thyroid function. 

Ready to get to the bottom of your thyroid symptoms? Book an appointment with one of our functional medicine providers today.

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