Association between thyroid function tests at baseline and the outcome of patients with sepsis or septic shock: a systematic review

Abstract

Introduction: The severity of critical illness is associated with various patterns of thyroid hormone abnormalities. We sought to evaluate whether the outcome of patients with, specifically, sepsis or septic shock is associated with the thyroid function tests evaluated at diagnosis or admission in the intensive care unit (ICU). Methods: We performed a systematic review of relevant studies by searching PubMed. Results: We included nine studies that all had a prospective cohort design. Seven involved children or neonates, and two involved adults. Mortality was the outcome evaluated in eight studies, while the length of ICU stay was evaluated in the remaining study. In univariate analysis, six of the nine included studies showed that either, free or total, triiodothyronine or thyroxine was lower in the group of patients with sepsis or septic shock who had unfavorable outcome than in those who had favorable outcome. Two other studies showed higher TSH values in the group of patients with unfavorable outcome. No significant relevant findings were observed in the remaining study. Regarding the correlation of sepsis prognostic scoring systems with thyroid function tests, the three studies that provided specific relevant data showed variable findings. Discussion: Most of the relevant studies identified favor the concept that decreased thyroid function at baseline might be associated with a worse outcome of patients with sepsis or septic shock. Although these findings are not consistent, the role of thyroid function in affecting or merely predicting the outcome of sepsis or septic shock merits further investigation.

Endocrine dysfunction in sepsis: a beneficial or deleterious host response?

“…6,40 It is believed that the thyroid dysfunction observed during sepsis constitutes part of an adaptive metabolic response in an attempt to increase resistance to different stressors by lowering the cellular metabolic activity. 41 The prevalence of thyroid abnormalities in the general population varies between 1% and 10%, which could explain the presence of various forms of thyroid dysfunction in some patients with sepsis. 41 Thyroid dysfunction in sepsis is often defined by the low T3 syndrome, euthyroid sick syndrome or nonthyroidal illness syndrome.…”

“…41 The prevalence of thyroid abnormalities in the general population varies between 1% and 10%, which could explain the presence of various forms of thyroid dysfunction in some patients with sepsis. 41 Thyroid dysfunction in sepsis is often defined by the low T3 syndrome, euthyroid sick syndrome or nonthyroidal illness syndrome. 6 The initial abnormality is a decrease in total T3 concentration secondary to a decrease of peripheral conversion of thyroxine (T4) to T3 by reducing 5'-deiodinase activity.…”

“…40 Several inflammatory cytokines (IL-1β, IL-6, and TNF-ɑ) can directly or indirectly suppress thyroid function at different levels, leading to a reduction in thyrotropin-releasing hormone (TRH) secretion at the level of the hypothalamus or a direct suppression of TSH release. 6,41 Activation and depression of hypothalamic-pituitary-adrenal (HPA) axis with biphasic vasopressin secretory response and inappropriately low levels compared to the severity of illness; it is not recommended as first line vasopressor and should be used in low dose in addition to vasopressors (norepinephrine)…”

“…40,41 There is little evidence regarding thyroid hormone substitution in human critical illness. 41 Some studies have shown that T4 substitution can result in reduction in the need for vasopressors in circulatory shock.…”

“…40,41 There is little evidence regarding thyroid hormone substitution in human critical illness. 41 Some studies have shown that T4 substitution can result in reduction in the need for vasopressors in circulatory shock. 42 Follow-up thyroid function tests are recommended if abnormal levels are detected during sepsis, as usually most of these abnormalities are transient and do not represent a true underlying thyroid disease.…”