ESPE Abstracts

Background: Primary congenital hypothyroidism can be classified into thyroid dysgenesis and thyroid dyshormonogenesis. Thyroid dysgenesis includes aplasia, hypoplasia, and ectopia. About one-third of ectopic thyroid is presented with congenital hypothyroidism, but sometimes it may be difficult to diagnose ectopic thyroid in infancy. Thyroid ultrasonography or scintigraphy can be used to diagnose thyroid dysgenesis, but sometimes it is hard to diagnose correctly by using one of them. The purpose of this study is to evaluate the diagnostic values of thyroid imaging studies in children referred for the suspected congenital hypothyroidism.

Subjects and Methods: Among children who underwent thyroid scintigraphy below 6 years of age between 2002 and 2017, subjects with the impression of congenital hypothyroidism and thyroid dysgenesis were included. Clinical features and thyroid imaging findings were reviewed and diagnostic values of thyroid imaging studies were analyzed based on the final diagnosis.

Results: A total of 19 children with thyroid ectopia or aplasia on thyroid scintigraphy were included in the study after reviewing 64 medical records of children who performed thyroid scintigraphy between 2002 and 2017. There are 5 males and 14 females. The mean age at 1^st visit was 4.5±9.8 months. The initial presentation was abnormal neonatal thyroid screening test (n=16, 84%), delayed development and low T₄ level (n=1), tongue base mass (n=1), and constipation (n=1). Four subjects were born as premature babies and 1 infant had schizencephaly. Initial results of thyroid sonography were as follows: ectopia (n=6), hypoplasia (n=8), and normal (n=5). The results of simultaneous thyroid scintigraphy were different: ectopia (n=10), invisible (n=9). After re-reading, final diagnosis was established as ectopia (n=9, 47%), hemithyroid (n=1), hypoplasia (n=3), aplasia (n=1), and normal thyroid gland (n=5). Thyroid scintigraphy showed better sensitivity in diagnosing ectopia, whereas sonography had better diagnostic value of normal eutopic thyroid gland.

Conclusions: This study showed that thyroid sonography and scintigraphy had different sensitivity or specificity in diagnosing specific type of thyroid dysgenesis. Thyroid sonography has better diagnostic value in the presence of normal eutopic thyroid gland, whereas scintigraphy is highly sensitive in diagnosing ectopia. Therefore, we recommend to use thyroid sonography as a first imaging modality to detect thyroid tissue, and thyroid scintigraphy will be required if thyroid hypoplasia or aplasia is suspected in thyroid sonography.