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Hypothalamic-pituitary-thyroid axis changes in children after cardiac surgery

Seth D Marks1, Christina Haines, Ivan M Rebeyka

  • 1Department of Pediatrics, Division of Endocrinology, University of Alberta, Stollery Children's Hospital, 1C4 Walter Mackenzie Health Sciences Centre, 8440 112th Street, Edmonton, Alberta, Canada. smarks@ualberta.ca

The Journal of Clinical Endocrinology and Metabolism
|June 4, 2009
PubMed

Insights

Nonthyroidal illness syndrome (NTIS) in critically ill children undergoing cardiac surgery is common and linked to poorer outcomes. Thyroid hormone levels remained abnormal for at least 8 days, indicating a prolonged impact.

Area of Science:

  • Pediatric Endocrinology
  • Critical Care Medicine
  • Thyroidology

Background:

  • Critical illness disrupts the hypothalamic-pituitary-thyroid axis, causing nonthyroidal illness syndrome (NTIS) with altered thyroid hormone levels.
  • The adaptive or maladaptive nature of NTIS and its impact on outcomes in pediatric critical illness remain unclear.
  • Limited data exist on NTIS in children, particularly those undergoing cardiac bypass surgery.

Purpose of the Study:

  • To investigate the natural history of NTIS in pediatric patients following cardiac bypass surgery.
  • To correlate NTIS biochemical changes with clinical outcomes and illness severity.
  • To assess the predictive value of thyroid function tests for clinical outcomes in this population.

Main Methods:

  • Thyroid function tests (TSH, T3, T3 uptake) were measured in 21 children (aged 1-11 years) preoperatively and postoperatively up to 7 days.
  • Illness severity was assessed using Pediatric Logistic Organ Dysfunction (PLOD) and inotrope scores.
  • Pediatric intensive care unit (PICU), hospital, and mechanical ventilation durations were recorded and analyzed.

Main Results:

  • All patients developed NTIS within 24 hours postoperatively; TSH normalized by postoperative day 4.
  • Thyroid hormone levels (Total T3, free T3 index, T3 uptake) remained below preoperative levels on postoperative day 7.
  • NTIS severity correlated with prolonged hospital stays, increased PICU and ventilation days, and higher PLOD and inotrope scores.
  • Early postoperative T3 measures predicted clinical outcomes, with illness severity preceding thyroid function changes.

Conclusions:

  • NTIS is prevalent in critically ill children after cardiac surgery, with some biochemical abnormalities persisting beyond 8 days.
  • The extent of NTIS is directly related to and predictive of clinical outcomes and illness severity in pediatric critical illness.
  • These findings suggest NTIS is a significant indicator of illness severity and prognosis in pediatric cardiac surgery patients.
Abstract

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