nonthyroidal illness (sick euthyroid syndrome)

(J Endocrinol 2010;205:1)

Gold: Low T3 Red: No check signle TSH in ICU, may check full panel TT4, fT3, T4, TSH Red: No need of thyroxine

• TFT abnormalities in Pts w/ severe nonthyroidal illness
  • (∴ in acute illness, ✓ TFTs if ↑ concern for thyroid disease);
  • may have acquired transient central hypothyroidism
• If thyroid dysfxn suspected in critically ill Pt, TSH alone not reliable; must measure total T4, free T4, & T3
• Mild illness:
  • ↓ T4 → T3 conversion,
  • ↑ rT3 → ↓ T3;
• in severe illness:
  • ↓ TBG & albumin,
  • ↑↑ rT3 → ↓↓ T3,
  • ↑ degradation of T4,
  • central ↓ TSH → ↓↓ T3, ↓↓ T4, ↓ free T4, ↓ TSH
• Recovery phase: ↑ TSH followed by recovery of T4 and then T3
• Replacement thyroxine not helpful or recommended for critically ill Pts w/ ↓ T3 and T4 unless other s/s of hypothyroidism