What is euthyroid sick syndrome?

Euthyroid sick syndrome occurs when thyroid function test results appear abnormal despite the thyroid gland functioning normally. This condition is often seen in people with severe illnesses, such as heart failure, chronic kidney disease, or infections, and can lead to low levels of T3 and T4, while TSH remains within the normal range. The syndrome usually resolves once the underlying illness is treated, so thyroid hormone replacement is typically not required. Your healthcare provider will interpret TFT results in the context of your overall health to determine the best course of action.