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