{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T22:09:56Z","timestamp":1778278196981,"version":"3.51.4"},"reference-count":23,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T00:00:00Z","timestamp":1777507200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Clinics and Practice"],"abstract":"<jats:p>Background: Non-thyroidal illness syndrome is frequent in critically ill patients, but the prognostic value of dynamic changes in thyroid function tests remains unclear. This study evaluated whether serial measurements of thyroid-stimulating hormone (TSH) and free triiodothyronine (FT3) provide additional predictive value for 30-day mortality beyond conventional severity scores in ICU patients. Methods: This single-center retrospective observational study included 74 adult patients treated for \u226572 h in a general ICU who had TSH and FT3 measured within 24 h of admission and repeated at 48\u201372 h. Patients aged 18 years or above admitted to the intensive care unit were included in the study. Demographic characteristics, comorbidities, APACHE II, SOFA, modified NUTRIC (mNUTRIC) scores, and routine laboratory data (including albumin, CRP, and lactate) were recorded. The primary outcome was 30-day mortality. Between-group comparisons were performed using t-tests, Mann\u2013Whitney U, and Chi-square tests. Variables significant in univariate analyses were entered into binary logistic regression models, and predictive performance was assessed using receiver operating characteristic (ROC) curves and the Youden index. Results: The mean age was 68.7 \u00b1 14.7 years, and 41.9% (n = 31) of the patients died within 30 days. Non-survivors had higher APACHE II, SOFA, and mNUTRIC scores and lower albumin, lymphocyte count, and second FT3 levels compared with survivors (all p \u2264 0.003). Baseline FT3 and TSH were not associated with mortality, whereas both the subsequent FT3 measurements and the \u0394T3 (variance in former to latter FT3) were remarkably predictive. The latter FT3 &lt; 1.63 pg\/mL produced an AUC of 0.835 (sensitivity: 77%, specificity: 74%), and a \u0394T3 log ratio threshold of \u22120.09 (\u224820% early FT3 decline) produced an AUC of 0.835 (sensitivity: 71%, specificity: 81%). The APACHE II + \u0394T3 (numeric) model showed the best discrimination (AUC: 0.921; sensitivity: 87.1%, specificity: 81.4%), outperforming APACHE II alone (AUC: 0.861). Conclusions: In critically ill adult patients, dynamic T3 kinetics\u2014particularly premature decline in FT3 within the first 72 h\u2014provide incremental prognostic value for 30-day mortality beyond APACHE II. Serial FT3 monitoring may help identify high-risk patients whose endocrine adaptation to critical illness is failing.<\/jats:p>","DOI":"10.3390\/clinpract16050087","type":"journal-article","created":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T10:47:28Z","timestamp":1777546048000},"page":"87","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Prognostic Significance of Dynamic Free T3 Changes in Critically Ill Patients"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1370-1696","authenticated-orcid":false,"given":"Yakup","family":"\u00d6zg\u00fcng\u00f6r","sequence":"first","affiliation":[{"name":"Department of General Intensive Care Unit, \u0130zmir City Hospital, Izmir 35530, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Burak Emre","family":"Gilik","sequence":"additional","affiliation":[{"name":"Department of General Intensive Care Unit, \u0130zmir City Hospital, Izmir 35530, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3831-9565","authenticated-orcid":false,"given":"Emre","family":"Karag\u00f6z","sequence":"additional","affiliation":[{"name":"Department of General Intensive Care Unit, \u0130zmir City Hospital, Izmir 35530, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8736-308X","authenticated-orcid":false,"given":"Hicret","family":"Yeniay","sequence":"additional","affiliation":[{"name":"Department of General Intensive Care, Bal\u0131kesir Atat\u00fcrk City Hospital, Bal\u0131kesir 10185, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7687-0924","authenticated-orcid":false,"given":"Mensure","family":"\u00c7ak\u0131rg\u00f6z","sequence":"additional","affiliation":[{"name":"Department of General Intensive Care Unit, \u0130zmir City Hospital, Izmir 35530, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"\u00d6zlem Melis Korkmaz","family":"\u00d6zg\u00fcng\u00f6r","sequence":"additional","affiliation":[{"name":"Department of Occupational and Environmental Diseases, Dokuz Eylul University Faculty of Medicine, Izmir 35340, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2009-1056","authenticated-orcid":false,"given":"\u0130hsan","family":"Birol","sequence":"additional","affiliation":[{"name":"Department of Intensive Care, Suat Seren Chest Diseases and Thoracic Surgery Training and Research Hospital, Izmir 35110, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"S\u0131la","family":"Seven","sequence":"additional","affiliation":[{"name":"Department of General Intensive Care Unit, \u0130zmir City Hospital, Izmir 35530, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Imam, S.K., and Ahmad, S.I. 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