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Interleukin-6 and thyroid hormone metabolism in pediatric cardiac surgery patients
Clarie K McMahon1, Irwin Klein, Kaie Ojamaa
1Department of Pediatric, North Shore-LIJ Health System, NYU School of Medicine, Manhasset, New York, USA.
Insights
Pediatric cardiac surgery patients experience low triiodothyronine (T3) levels post-operation. This study links elevated interleukin-6 (IL-6) to reduced T3, suggesting cytokine modulation as a potential treatment.
Area of Science:
- Pediatric Endocrinology
- Cardiovascular Surgery
- Immunology
Background:
- Children undergoing cardiac surgery often exhibit low serum triiodothyronine (T3) levels postoperatively.
- Proinflammatory cytokines, like interleukin-6 (IL-6), are suspected to inhibit the conversion of thyroxine (T4) to T3 in the liver.
Purpose of the Study:
- To investigate the relationship between serum IL-6 levels and triiodothyronine (T3) levels in pediatric patients during the early postoperative period after cardiopulmonary bypass surgery.
Main Methods:
- Serum T3 and IL-6 levels were measured in 16 pediatric patients (mean age 28 days) during the first 4 days after cardiac surgery.
- Preoperative and serial postoperative measurements were taken to track changes.
Main Results:
- A significant decrease in mean serum T3 from 164 ng/dL preoperatively to a nadir of 43 ng/dL within 48 hours post-surgery was observed.
- Serum IL-6 levels significantly increased from 16 pg/mL preoperatively to a peak of 374 pg/mL 2-3 hours after surgery.
- A positive correlation (r² = 0.507) was found between peak IL-6 levels and the lowest T3 levels observed.
Conclusions:
- Elevated IL-6 levels correlate with reduced T3 levels in pediatric cardiac surgery patients.
- Targeting the reduction of proinflammatory cytokines in the postoperative period may help prevent low T3 levels and associated morbidity.
Abstract:
Pediatric patients undergoing cardiac surgery have been reported to have low serum triiodothyronine (T(3)) levels in the postoperative period. The cause of this dysfunction is not known, although proinflammatory cytokines such as interleukin-6 (IL-6) have been implicated in the inhibition of hepatic conversion of thyroxine (T(4)) to T(3). This study measured serum levels of IL-6 and T(3) during the first 4 postoperative days in 16 children (mean age, 28 +/- 7 days) undergoing cardiopulmonary bypass surgery. The mean preoperative serum total T(3) level was 164 +/- 30 ng/dL (2.5 +/- 0.5 nmol/L) that decreased significantly to a nadir of 43 +/- 8 ng/dL (0.6 +/- 0.01 nmol/L) within 48 hours after surgery. Serum IL-6 levels increased significantly from 16 +/- 7 pg/mL preoperatively to a peak value of 374 +/- 134 pg/mL measured 2-3 hours after surgery. A positive correlation (r(2) = 0.507) was found between the peak serum level of IL-6 and the lowest serum T(3) level in each patient attained during the 4 postoperative days. Potential treatments directed toward diminishing the rise in proinflammatory cytokines in the immediate postoperative period may prove effective in preventing the low serum T(3) in children undergoing cardiac surgery, and thus diminish the associated postoperative morbidity.