Lower free triiodothyronine (fT3) levels in cirrhosis are linked to systemic inflammation, higher risk of acute-on-chronic liver failure, and mortality.

Background & Aims: Advanced chronic liver disease (ACLD) may affect thyroid hormone homeostasis. We aimed to analyze the pituitary-thyroid axis in ACLD and the prognostic value of free triiodothyronine (fT3). Methods: Patients with ACLD (liver stiffness measurement [LSM] ≥10 kPa) undergoing hepatic venous pressure gradient (HVPG) measurement between June 2009 and September 2022 and available fT3 levels were included. Clinical stages of ACLD were defined as follows: probable ACLD (pACLD; LSM ≥10 kPa and HVPG ≤5 mmHg), S0 (mild portal hypertension [PH]; HVPG 6-9 mmHg), S1 (clinically significant PH), S2 (clinically significant PH with varices), S3 (past variceal bleeding), S4 (past/current non-bleeding hepatic decompensation), and S5 (further decompensation). Results: Among 297 patients with ACLD, 129 were compensated (pACLD, n = 10; S0, n = 33; S1, n = 42; S2, n = 44), whereas 168 were decompensated (S3, n = 12; S4, n = 97; S5, n = 59). Median levels of thyroid-stimulating hormone (TSH) numerically increased with progressive ACLD stage (from 1.2 μIU/ml [pACLD] to 1.5 μIU/ml [S5]; Conclusions: Increasing TSH and declining fT3 levels are observed with progressive ACLD stages. The association of TSH and fT3 with systemic inflammation suggests a liver disease-associated non-thyroidal illness syndrome. Lower fT3 levels in patients with ACLD indicate increased risk for decompensation, acute-on-chronic liver failure, and liver-related death. Impact and Implications: In a large well-characterized cohort of patients with advanced chronic liver disease (ACLD), we found a decline of free triiodothyronine (fT3) throughout the clinical stages of ACLD, paralleled by a numerical increase of thyroid-stimulating hormone (TSH). This suggests a progressive development of a non-thyroidal illness syndrome in association with ACLD severity. Importantly, C-reactive protein independently correlated with TSH and fT3, linking thyroid dysbalance in ACLD to systemic inflammation. Lower fT3 indicated an increased risk for subsequent development of hepatic decompensation, acute-on-chronic liver failure, and liver-related death. Clinical trial number: Vienna Cirrhosis Study (VICIS; NCT: NCT03267615).