Treatment of euthyroid sick syndrome

Over the years, I have listened to many presentations reviewing the pros vs. cons of treating euthyroid sick syndrome, also known as non-thyroidal illness syndrome. Most of these lectures were interesting and intellectually stimulating. However, as a clinician faced with choosing whether to treat or not treat, such academic discussions are sometimes less than helpful.

In the December 2008 issue of Endocrine Practice, Alan P. Farwell, MD, writes a commentary on why thyroid hormone therapy is not indicated in the majority of patients with euthyroid sick syndrome. He points out the limited evidence to suggest benefit but also notes there is no evidence that it causes harm. He suggests further study is merited in whether liothyronine (T₃) has any benefit in congestive heart failure as well as increasing organs available to harvest from brain-dead donors. He concludes that otherwise there is no clear evidence that thyroid HT is beneficial in patients with euthyroid sick syndrome.

In an informal, unscientific survey of several endocrinologists I know, I found that as a rule most do not treat, although some still do. Their position seems to depend on whether they believe euthyroid sick syndrome is a normal physiologic effect of severe illness or if it represents a maladaptive response that needs therapy. Space limitations prevent me from going into detail reviewing the merits and limitations of each point of view.

However, I do have one caveat. No matter what side of the issue you are on: be cautious. Even if mild laboratory abnormalities may not need to be treated, be aware that other diagnoses are possible. I once saw a woman who was hospitalized with congestive heart failure. Her thyroid-stimulating hormone level was fully suppressed but was written off as her being euthyroid sick. It was only when she developed atrial fibrillation that additional studies were ordered. Her free T₃ was elevated, and free thyroxine was high normal. She had hyperthyroidism, not euthyroid sick syndrome.

More challenging are patients with undiagnosed hypopituitarism. Their thyroid studies can be difficult to distinguish from someone with euthyroid sick syndrome. I have seen several cases of panhypopituitarism in which the only clue was slightly abnormal thyroid studies. The diagnosis was missed at first. It was only when an astute clinician evaluated further that the hypopituitarism was recognized. Not only did the patient have central hypothyroidism but also central hypoadrenalism and other hormonal deficiencies.

I look forward to your comments.

Farwell AP. Endocr Pract. 2008;14:1180-1187.