Man palpating his neck with thyroid gland superimposed on throat and text bubble saying confusing thyroid blood work: non-thyroidal illness

When your doctor assesses or treats your thyroid function, they will usually rely on blood work. In a lot of patients suffering from hypothyroidism, blood test results are confusing, and don’t follow the expected findings; one cause is non-thyroidal illness.

Normal Testing

Usually, testing is straightforward and results align with symptoms. In cases of hypothyroidism, we expect elevated TSH and diminished T3 and T4. With hyperthyroidism, we expect low TSH and elevated T3 and T4.

a schematic showing thyroid metabolism in hypothyroidism, including T3 and T4 and how when they drop, TSH will increase
thyroid physiology involved in hyperthyroidism showing T3 and T4 hormones have increased expression while TSH drops

Non-Thyroidal Illness (aka Sick Euthyroid Syndrome)

This is defined as an abnormality of hypothalamus-pituitary-thyroid (HPT) function that is considered secondary to something else. In other words, the thyroid lab values are off, and symptoms may be present, but it’s not due to a dysfunctional hypothalamus, pituitary or thyroid gland. Click here to review how the hypothalamus, pituitary and thyroid work together. Something else in the body is not right and affects this HPT system indirectly. It is considered an adaptive, protective mechanism.

So Non-thyroidal illness (NTI) is also referred to as sick euthyroid syndrome. The name is accurate – abnormal thyroid blood tests can be caused by various illnesses that do not directly involve the thyroid gland [3]. This phenomenon is very common, and occurs in as many as 70% of patients who have been admitted to a hospital. This is a well-known phenomenon in chronically ill patients and explains a person going into the hospital for one thing and coming out with thyroid medications. As you will see, treatment must be carefully considered. There is no evidence that giving thyroid medications to people with non-thyroidal illness is useful [1].

Common Presentation of NTI

One of the classic presentations is raised thyroid hormones (T3 and T4) with a non-suppressed TSH [2]. Typically, these changes are seen as early as 24 hours after onset of NTI [1], [2].

This type of presentation has been reported in a wide range of conditions:

  • Myocardial infarction
  • Post-surgery
  • Chronic liver disease
  • Chronic renal disease
  • Poor nutrition/starvation
  • Sepsis
  • Burns
  • Malignancy
  • Acute psychiatric states: abnormal result should revert with recovery, recovery noted to be about <2 weeks

Treatment Needs to be Carefully Considered

As mentioned above, this is a common phenomenon and treating based on the lab values alone can be done erroneously. If Thyroid hormone levels from prior to illness is available, it’s helpful in confirming NTI involvement [2]. Recognition is critical because therapy is often not needed and could be detrimental.

These anomalous results of thyroid function tests often revert to normal once the patient recovers from the illness [1], [2].


Those patients with confusing thyroid blood work must ensure all causative factors are investigated. Non-thyroidal illness must be considered in those with other illnesses. Understanding why thyroid numbers are off is important because treatment options vary drastically.


Interested in learning more?

Read on in our series of articles on Thyroid Health!

About the Author - Dr. Johann de Chickera

man facing camera

Dr. Johann is a fully licensed Naturopathic Doctor. His approach emphasizes the importance of living a healthy lifestyle and improving one’s health naturally. Dr. Johann obtained a Doctor of Naturopathy at the Canadian College of Naturopathic Medicine (CCNM). Education at CCNM is a vigorous four years, with a curriculum involving biomedical sciences, physical diagnosis, clinical nutrition, traditional Chinese medicine and acupuncture, botanical (herbal) medicine, physical medicine, homeopathy and lifestyle management.

While Dr. Johann has a general practice, he focuses on fertility, hormonal imbalances, gut health, and autoimmune disease.

To book in please call us at (519) 442-2206 or click here.

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