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].

Summary

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.