Pulmonary effects of triiodothyronine (T3) and hydrocortisone (HC) supplementation in preterm infants less than 30 weeks gestation:: Results of the THORN trial -: Thyroid hormone replacement in neonates

The THORN trial was a multicenter, randomized, double-blind, placebo-controlled clinical trial to test the hypothesis that administration of triiodothyronine (T-3) and hydrocortisone would decrease mortality and respiratory morbidity in preterm infants of less than 30 wk gestation. Two hundred fifty-three infants were randomized to receive either 6 mug.kg(-1).d(-1) of T-3 with 1 mg.kg(-1).d(-1) of hydrocortisone or 5% dextrose (placebo) as a continuous i.v. infusion for 7 d. The dose was halved on d 5. Our first primary outcome was death or ventilator dependence at 1 wk, and the second was death or oxygen dependence at 2 wk. The overall mortality rate for both groups was 11.4%. Relative risk of death or ventilator dependence at 1 wk, treated versus placebo, was 0.87, p = 0.2, and death or oxygen dependence at 2 wk, 1.00, p = 0.9. We examined the relationship between free T-3 (FT3) and free thyroxine (FT4) levels in the first 7 d and the primary outcome death or ventilator dependence at 1 wk in all 253 babies. We found significant positive correlations of p = 0.05 for FT3 and p = 0.002 for FT4. Thus the higher the FT3 and FT4 levels, the better the outcome. No beneficial effects of T-3 and hydrocortisone were shown. In this study, although FT3 levels were doubled by the treatment infusion, FT4 levels were significantly suppressed. The lack of any beneficial effect of T-3 in our study may be explained by suppression of FT4 in the treatment group.