Preterm infants are jeopardized by the immature thyroid system. Dexamethasone is a widely used drug well known to inhibit the peripheral thyroxine (T4) conversion. We therefore studied the concentrations of T4 and T3 in 22 ELBW infants.Methods: We obtained blood samples at delivery, 4, 7, and 14 days thereafter in (G1) 12 ELBW infants treated with dexamethasone during the first days of live (0.5 mg/kg day) because of arterial hypotension or severe lung disease and in (G2) 10 ELBW infants without dexamethasone.There was no physiological increase in T3 serum concentrations after birth in G1, whereas T4 and TSH showed a similar course in both groups (not shown). T3 concentrations were significantly lower in the dexamethasone treated infants at day 7 and 14.Conclusion: Our data show evidence that the immature thyroid function of ELBW infants (hypothyroxinemia and transient primary hypothroidism) is further adversely affected by dexamethasone.
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