Thyroid function in 76 sick preterm infants 30-36 weeks: results from a longitudinal study

Abstract

Aim: To assess thyroid function in 76 sick preterm infants 30-36 weeks gestational age.

Patients and methods: Measurement of serum TSH, T4, T3, free T4 and rT3 in the mother and cord at delivery, and in the infant at 1 and 24 hours, 1 and 3 weeks, 2, 4, 6 and 12 months of postnatal age. These values were compared with those of 75 healthy age-matched controls. Gestational age was 30 weeks in 24, 31 weeks in 23, 32 weeks in 13, 33 weeks in 13, 34 weeks in one, 35 weeks in one and 36 weeks in one. Hypothyroxinemia at each postnatal age was defined as serum free T4 values under -2 SD of the mean of controls.

Results: Forty-four patients were normothy-roxinemic at all times, and 32 presented hypothyroxinemia at 24 hours (29 patients), 1 week (seven patients) and 3 weeks (two patients). Follow-up of 31 patients who were normothyroxinemic at 24 hours of life showed that at one week three (9.7%) were hypothyroxinemic and at 3 weeks all were normothyroxinemic. At 24 hours of life, all patients with patent ductus arteriosus and all patients treated with dopamine were in the hypothyroxinemic range.

Conclusion: Hypothyroxinemia may be present in sick preterm infants 30-36 weeks of gestational age, particularly in those treated with dopamine and/or presenting patent ductus arteriosus.