Among patients undergoing surgery for a brain tumor, low T3 (triiodothyronine) syndrome has been found to be predictive of unfavorable clinical outcomes and depressive symptoms.
Low T3 syndrome is a term used to describe the finding of low blood serum concentrations of T3, which can be accompanied by abnormal T4 (thyroxine) to T3 conversion and high concentrations of reverse T3 (rT3) without any obvious sign of thyroid disease. Previous reports have shown that the finding of low levels of T3 in critically ill patients and in patients undergoing surgery for some disorders is widespread and associated with unfavorable clinical outcomes.
This association of low T3 and poor outcomes was investigated in patients undergoing brain tumor surgery by Adomas Bunevicius, MD, PhD, of Lithuanian University of Health Sciences and colleagues there and at the University of North Carolina at Chapel Hill. They performed perioperative thyroid function tests and also examined whether there was an association between low T3 syndrome and symptoms of anxiety and depression. These are common complications in patients harboring brain tumors and are associated with poor prognoses.
Thyroid function profiles were evaluated in 90 patients (median age 55 years, 71% women) on the morning of brain surgery and again on the following morning. If patients were found to have a free T3 level of 3.1 pmol/L or less, they were diagnosed as having low T3 syndrome.
Low T3 syndrome occurred in 38% of these patients before brain tumor surgery and in 54% of the patients after surgery. In comparing preoperative and postoperative thyroid hormone profiles, significant decreases occurred in the concentration of free T3, the concentration of thyroid-stimulating hormone, and the conversion of T4 to T3, while significant increases occurred in the concentration of free T4 (all P< .001). This study was published in the Journal of Neurosurgery (2013; doi:10.3171/2013.1.JNS121696).
Perioperative low T3 syndrome was associated with a five-fold increased risk of unfavorable outcome at the time of hospital discharge, compared to patients with normal T3 concentrations. A significantly increased risk of unfavorable outcome was associated with preoperative and postoperative low T3 syndrome was confirmed in analyses that considered patient age and sex, preoperative impairments in function, histologic type of brain tumor, and previous treatment for brain tumor.
Postoperative scores for symptoms of depression and anxiety significantly improved compared with preoperative scores. The risk of preoperative symptoms of depression was found to be increased four-fold in patients with preoperative low T3 syndrome, and the association between these two factors was confirmed in analyses that accounted for sociodemographic and clinical factors.
These findings indicate that diagnosis and preoperative management of low T3 syndrome should be considered in patients undergoing surgery for a brain tumor. Bunevicius added, “Thyroid hormone concentrations can easily be investigated in routine clinical settings. The tests are inexpensive and readily available worldwide. Thyroid hormone concentrations can be potentially relevant for risk stratification in patients undergoing surgery for brain tumors.”