Reduction of mortality rate in premature infants by substitution of thyroid hormones

Abstract

Our previous examinations had shown that 9 of 13 premature infants with severe respiratory distress had hypothyroid T4-values. On the basis of these results a prospective study was initiated. Every second neonate born after less than 37 weeks gestation or weighing less than 2200 g and admitted to our intensive care unit since Janary 1979 received a prophylactic dose of 25 μg l-Thyroxine and 5 μg Tri-iodothyronine daily. Five of the patients inadvertently did not receive the drug and were included in the non-treated group which thus numbered 55. Both groups were nearly identical with regard to gestational age, birth weight and Apgar score.

In the treated group of 45 infants three (=6.6%) died. In the untreated group of 55 infants 16 (=29%) died. The probability that the different mortality in the two groups was due to chance alone is less than 0.5% (χ²-test: P<0.005). In 14 of the 55 non-treated patients transient hypothyroidism developed. Five patients with transient hypothyroidism and 2 patients with low T4-values without a TSH-increase were treated with thyroid hormone after ascertainment of their serum thyroxine levels and six survived.

The analysis of the prophylactically treated cases showed that the dosage of 25 μg l-Thyroxine and 5 μg Tri-iodothyronine in critically ill infants (i.e., those who were mechanically ventilated or had sepsis) was rarely sufficient to produce normal serum thyroxine levels. In these children thyroxine usually rose to normal levels only when they had passed the acute stage of the disease. It therefore seems advisable to double the dose of thyroid hormone during the acute stage of the disease.