ESPE Abstracts

Background: Congenital hypothyroidism (CH) is one of most common endocrine disease in childhood. If unteated, it is one of the leading causes of childhood intellectual disability. CH can be permanent, or can be transient in which thyroid function is spontaneously recovered. It is also known that among children with congenital hypothyroidism, the proportion of transient cases is higher in preterm than in full term babies. But there are few, if any, large studies which evaluated the risk factors of permanent congenital hypothyroidism. And most of previvous studies involved only full-term infants. So, in this study, we investigated the proportion of permanent hypothyroidism and the difference between transient and permanent hypothyroidism group, in CH patients including both term and preterm infants. We also tried to find out the predictive factors of permanent hypothyroidism.

Methods: In CH patients, we gathered information about demographic characteristics and information about thyroid function test and levothyroxine medication by retrospective chart review. Discontinuation of levothyroxine was tried when the patients were 3 years of age. Thyroid function test was followed up for more than 6 months after discontinuation. We compared the clinical characteristics between permanent and transient group and investigated the risk factors for permanent CH.

Results: Patients were 82 infants who were born between July 2005–July 2014 and treated for congenital hypothyroidism in Gyeongsang National University Hospital (52 preterm and 30 full-term infants). Fourty-two (51.2%) were males. Eleven (13.4%) were permanent hypothyroidism. There was no difference in proportion of permanent cases between preterm and full term groups (9.6 vs 20.0%, P=0.198). Compared with transient cases, those with permanent hypothyroidism had higher levethyroxine dose at 1 yr, 2yr and at discoutinuation. levothyroxine dose at discontinuation of 2.88 μg/kg could suggest permanent CH at a sensitivity of 90% and a specificity of 71%, with an area under the ROC curve of 0.864.

Conclusion: Majority of CH patients discontinued successfully. Higher levothyroxine dose at discontinuation was found to be a predictive factor of permanent hypothyroidism.