Incidence and Risk Factor of Permanent Hypothyroidism in Preterm Infants

Background: To investigate the incidence and risk factors of permanent hypothyroidism in premature infants diagnosed with congenital hypothyroidism. Methods: A retrospective review of medical records of preterm infants was performed between March 2010 and December 2013. We included infants who were treated with thyroxine after being diagnosed with congenital hypothyroidism and persistent hyperthyrotropinemia. Exclusion criteria included an infants who were lost to follow up or earlier discontinuation of thyroxine medication and had proven permanent hypothyroidism. We performed trial offtherapy at 36 months of age. Results: A total of 49 infants were eligible for trial off-therapy at age 3 years. Permanent and transient hypothyroidism was diagnosed in 12 and 37 infants, respectively. Persistent hypothyroidism was more frequent in the infants with high TSH and low FT4 levels at initial screening and high incidence in abnormalities in thyroid imaging work-ups and positive anti-thyroid antibodies. Moreover, the average thyroxine dosage during follow-up was significantly higher in infants with persistent hypothyroidism (p<0.05). Conclusion: Thyroid dysfunction is common in preterm infants, and nearly 80% of infants showed transient hypothyroidism. Therefore, if there is no other risk factor for permanent hypothyroidism, it is possible to consider an earlier trail off- therapy for preterm infants.