Thyroid Function, Reverse Triiodothyronine, and Mortality in Critically Ill Clinical Patients

Abstract

A bstract Background To evaluate the association of thyroid hormones changes, including increased reverse triiodothyronine (rT3) level, with critically ill clinical patients´ mortality. Patients and methods This study analyzed the observational data prospectively collected over 8 months (2018) in an adult intensive care unit (ICU) in Brasilia, Brazil. All consecutive ICU-admitted clinical patients were included. Thyroxine (T4), free thyroxine (fT4), triiodothyronine (T3), free triiodothyronine (fT3), rT3, and thyroid-stimulating hormone (TSH) were collected within 48 hours of ICU admission. Patients with hypothyroidism or hyperthyroidism who were previously diagnosed were excluded. Results Of 353 included patients, age was 68.5 ± 19.0 years, sequential organ failure assessment (SOFA) score was 3.3 ± 2.9, and Acute Physiology and Chronic Health Evaluation II (APACHE II) was 17.1 ± 7.9. ICU mortality was 17.6% ( n = 62). Non-survivor patients had a higher incidence of increased rT3 (69.3 vs 59.2%, p = 0.042), lower incidence of low T4 (4.8 vs 9.7%, p = 0.045), and increased age (75.2 ± 16.3 years vs 67.1 ± 19.3 years, p = 0.001), SOFA (3.0 ± 0.4 vs 2.8 ± 2.6, p <0.001), and APACHE II (23.5 ± 7.5 vs 15.7 ± 7.2, p <0.001). Alterations in other thyroid hormones did not show association with mortality. Increased rT3 [odds ratio (OR): 2.436; 95% confidence interval (CI): 1.023–5.800; p = 0.020] and APACHE II (OR: 1.083, 95% CI: 1.012–1.158; p = 0.044) were associated with ICU mortality in the multivariate analysis. Conclusion Increased rT3 was independently associated with increased ICU mortality. In contrast, other thyroid hormone alterations did not show an association with mortality. Determining rT3 levels may be a helpful test to identify an increased risk for ICU mortality in clinical patients. How to cite this article da Silveira CDG, de Vasconcelos FPJ, Moura EB, da Silveira BTG, Amorim FFP, Shintaku LS, et al. Thyroid Function, Reverse Triiodothyronine, and Mortality in Critically Ill Clinical Patients. Indian J Crit Care Med 2021;25(10):1161–1166.

Adaptive Effects of Endocrine Hormones on Metabolism of Macronutrients during Fasting and Starvation: A Scoping Review

“…Until recently, rT 3 has been identified as an inactive metabolite of thyroid hormone metabolism [ 200 ]. There have been reports indicating that rT 3 may produce unfavorable outcomes, including end-stage chronic kidney disease, acute myocardial infarction, hepatic diseases, and increased intensive care unit (ICU) mortality [ 201 ].…”

“…It has been suggested that rT 3 levels are increased when there is food deprivation [ 38 , 105 , 155 ], and rT 3 may produce unfavorable clinical outcomes [ 201 ]. It is, however, unclear whether increased rT 3 levels during fasting or starvation are linked to unfavorable clinical outcomes.…”

Frequency of non-thyroidal illness syndrome in pediatric patients with sepsis and septic shock

“…One mechanism that could explain the isolated elevation of rT3 levels in D-1 is drop of its clearance in the liver that appears earlier, also leading to a fall in the FT3 levels. The low half-life of rT3 (around 3 h compared to 24 h for T3) makes rT3 a sensitive and earliest marker for acute changes in thyroid hormones' metabolism [32]. Similarly, Hosny et al 2015 found that only FT3 levels measured during follow up in day 5 was significantly decreased in nonsurvivors than survivors [33].…”

Evaluation of non-thyroidal illness syndrome in shock patients admitted to pediatric intensive care unit in a developing country

“…It is noteworthy that all participants in the study had increased levels of rT3, which indicates its potential as a sensitive and early indicator for detecting acute alterations in thyroid hormone metabolism. The short half-life of rT3, approximately 3 h, further enhances its effectiveness in promptly identifying these changes [ 28 ].…”