- Description
- A change in thyroid hormone levels (typically decreased) that occurs in severe illness or severe physical stress
- Common in intensive care patients and associated with morbidity and mortality
- Also known as euthyroid sick syndrome (ESS)
- Pathophysiology: multifactorial and not fully understood
- Increased pro-inflammatory cytokines (e.g., IL-6, TNF-α) inhibit 5’-deiodinase activity.
- Result: ↓ Peripheral conversion of T4 to T3.
- Metabolism is shunted towards the production of the inactive isomer, Reverse T3 (rT3).
- Clinical features
- Signs and symptoms of the underlying illness
- Typically no classic symptoms of hyper- or hypothyroidism
- Diagnostics
- Early: Low T3, normal TSH & T4
- Late: Low T3, TSH & T4