Association of severe respiratory distress syndrome and thyroid agenesis in a term neonate

Case report: A neonate was born by vaginal route at the gestational age of 38 weeks after a normal pregnancy. At birth the baby unexpectedly showed no signs of spontaneous breathing and was immediately intubated. Respiratory support was continued but with gradual evolution towards respiratory insufficiency (oxygenation index of 25–35) with subsequent referral to our unit for ECMO treatment on day 3.

On admission, clinical examination of the neonate showed a large fontanel with large protruding tongue and icterus. On neurological examination, there was a striking hypotonia ('frog'like position). X-ray was consisted with lung hypoplasia and signs of hyaline membrane disease.

Based on these clinical signs, thyroid function was evaluated and severe hypothyroidism (TSH 126,9 mIU/L; T4 1,4µg/dL; T3 43 ng/dl) was documented. Nuclear scan showed no capitation of Technetium suggestive of agenesis of the thyroid gland. Ossification of the tibia (Beclar) was consisted with delayed bone maturation. Substitution with elthyrone was immediately initiated (20µg/kg) and increased to 30µg/kg because of persisting low values. With this substitution the baby euthyroidism was achieved. Improving thyroid function was accompanied by in improved oxygenation.

Discussion: Thyroid agenesis should be screened for in term neonates referred for ECMO with unexplained respiratory distress syndrome (RDS).

There are arguments in literature that RDS in these extremely hypothyroid infants could be explained by delayed maturation of surfactant metabolism.