High Prevalence of Non-thyroidal Illness Syndrome in Patients with Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-analysis

Our aim was to estimate the prevalence of non-thyroidal illness syndrome in individuals with chronic obstructive pulmonary disease (COPD). A systematic review and meta-analysis of studies indexed in Embase, ScienceDirect, PubMed, Virtual Health Library, Web of Science, and Cochrane Library from inception through December 31, 2023, was performed. The protocol was registered in PROSPERO (CRD42024492108). Pooled prevalence and 95% CIs were calculated using the DerSimonian–Laird random-effects model, and heterogeneity was assessed with the I2 statistic. Meta-regression analyses examined the influence of age, sex, and smoking status. Subgroup and sensitivity analyses were performed, and associations with arterial blood gas parameters (PaO₂, PaCO₂, and SaO₂) were evaluated using the inverse-variance method within a random-effects framework. Eleven studies including 1005 chronic obstructive pulmonary disease patients met the inclusion criteria. The overall pooled prevalence of non-thyroidal illness syndrome was 44.2% (95% CI, 30.0-58.4%) with high heterogeneity (I2, 96.1%). Non-thyroidal illness syndrome was more common during acute exacerbations (54.5%) than in stable disease (13.8%). Meta-regression analyses showed that age, sex, and smoking status did not significantly account for heterogeneity. Among arterial blood gas parameters, a modest but statistically significant reduction in SaO₂ was observed in patients with non-thyroidal illness syndrome compared with those without (−2.65%, 95% CI, −4.56 to −0.74). No significant differences were detected for PaO₂ or PaCO₂. As a conclusion, non-thyroidal illness syndrome is a common finding in patients with COPD, particularly during acute exacerbations, and is associated with reduced oxygen saturation. These findings highlight the importance of monitoring thyroid function and oxygenation in this population. Cite this article as: Vázquez PF, Diez-Manglano J. High prevalence of non-thyroidal illness syndrome in patients with chronic obstructive pulmonary disease: A systematic review and metaanalysis. Eurasian J Med. 2026, 58(3), 1290, doi: 10.5152/eurasianjmed.2026.251290