Introduction 

Euthyroid sick syndrome is a clinical condition characterized by low thyroid hormone levels  in clinically euthyroid patients with nonthyroidal systemic illness

-it can be precipitated by stresses such as chronic liver failure, renal failure, malnutrition, fasting, starvation, anorexia, diabetic ketosis, and sepsis 

-The first testing abnormality to manifest is low T3 level

Symptoms & Signs 

No signs or symptoms of thyroid dysfunction 

Diagnosis 

Patient’s setting: critical illness, chronic illness, ICU admission etc

No clinical manifestations of thyroid dysfunction 

Labs: TSH: Normal or low 

T4 : Normal or low 

T3, total and free : Low 

Reverse T3 (rT3): High or normal 

Treatment: 

-Treat the underlying nonthyroid illness 

-Thyroid hormone replacement is not beneficial