Postnatal administration of dexamethasone for weaning off the ventilator affects thyroid function.

BACKGROUND

Very preterm neonates are at risk of hypothyroxinemia because of prematurity as well as because of neonatal disease. Hypothyroxinemia is associated with impaired developmental outcome. Preterm infants who cannot be weaned from the ventilator can be treated with dexamethasone. Glucocorticoid administration has been found to alter thyroid hormone parameters. Therefore, dexamethasone treatment in these infants might additionally impair their thyroid function, which could have consequences for developmental outcome.

OBJECTIVE

To assess what changes in thyroid function occur in the first hours after initiating dexamethasone treatment in ventilated preterm infants.

METHODS

Preterm infants, in whom the decision was taken to start dexamethasone treatment, were included. Thyroxine (T(4)), 3,5,3'-triiodothyronine (T(3)), reverse T(3) (rT(3)), thyroid-stimulating hormone (TSH) and cortisol were determined before and 6-9 h after administration of the first dose of a postnatal dexamethasone course. Details of clinical condition were recorded at both time points.

RESULTS

Sixteen very preterm infants were included at a median age of 20 days. While clinical condition was stable between start of dexamethasone and 6-9 h thereafter, TSH and T(3) levels decreased significantly. rT(3) levels significantly increased, resulting in a decrease in the T(3)/rT(3) ratio. There was no statistically significant effect on the levels of T(4).

CONCLUSION

Postnatal dexamethasone administration negatively affects thyroid functioning the preterm infant with severe chronic lung disease.