Thyroid hormones implication in severe community-acquired pneumonia (SCAP): Relationship with survival, outcomes and clinical complications

Background: The low thyroid hormone levels in the absence of primary thyroid disease have proved to be predictive of outcomes and disease severity in critical illness. We aimed to assess thyroid function in SCAP patients requiring intensive care unit (ICU) admission and it's association with in-hospital outcomes, SCAP complications, need for invasive mechanical ventilation (IMV) and vasopressor support. Methods: 40 ICU patients with SCAP CURB-65 class 3-5 were enrolled. Control group included 16 healthy subjects. X-ray examination, free triiodthyronine (fT3), free tetraiodthyronine (fT4), thyroid stimulating hormone (TSH) levels measurement were performed within the first 24 hours after admission. Results: fT3 initial values decreased with increasing severity of CAP (r=-0,75; p=0,0007). fT3 and TSH levels were lower in non-survivors vs in survivors [median] [2,8 vs 4,6 pmol/l, p=0,008 and 0,89 vs 2,6 mMU/l, p=0,037] and revealed correlation with in-hospital mortality (IHM) (r= -0,67; p=0,003 and r= -0,54; p=0,031 respectively). Longer in-hospital stay was associated with higher TSH (r=0,56; p=0,017) and lower fT4 values on admission (r= -0,44; p=0,05). Necrotising pneumonia (NP) developed in patients with lower fT4 levels vs those without destructive lung changes [16,9 vs19,1 pmol/l, p=0,042]. fT3 correlated with need for IMV (r= -0,71; p=0,001) and was lower in patients requiring IMV [2,86 vs 4,8 pmol/l, p=0,005]. Conclu sions:Thyroid hormone values in SCAP patients are reliable markers of diseases severity, high risk of IHM and NP development and can be helpful in identifying patients requiring IMV and predicting length of in-hospital stay.