Low T3 syndrome in children with aggressive mature B-cell non-Hodgkin lymphoma

Low triiodothyronine (T3) syndrome, also known as non-thyroidal illness syndrome (NTIS), was one of the common endocrinopathies in critical illness. The potential impacts of low T3 syndrome on survival, endocrine function, and nutritional status of patients with aggressive mature B-cell non-Hodgkin lymphoma (NHL) needed to be explored. We enrolled 225 patients. T3 levels were captured when starting chemotherapy, finishing chemotherapy, and at the first follow-up visit from 6 months after chemotherapy. Latest ultrasound results were recorded. Kaplan-Meier curves were used to compare overall survival (OS) or progression-free survival (PFS). We performed Cox's proportional hazards regression model to analyze prognostic factors of OS and PFS. Ultrasound abnormality and weight gain were tested with the χ² test. The percentage of patients with low T3 syndrome decreased from 55.1% (124 out of 225) to 2.0% (4 out of 201), then further dropped down to 0 (0 out of 173). With a median follow-up of 32.9 months, low T3 syndrome was identified as a statistically significant factor affecting both OS (p = .047; hazard ratio [HR] = 8.18, 95% CI: 1.03-64.97) and PFS (p = .049; HR = 4.64, 95% CI: 1.01-21.31) in multivariate analysis. No significant effects of low T3 syndrome on abnormal thyroid ultrasound results and weight gain were found. In conclusion, low T3 syndrome has a high incidence in pediatric patients with aggressive mature B-cell NHL, and low T3 syndrome has a significant impact on long-term survival. It appears transient and could not contribute to impaired thyroid function.