Classification of congenital hypothyroidism based on scintigraphy, ultrasonography and the serum thyroglobulin level

In the present study, infants with congenital hypothyroidism discovered on neonatal mass screening were examined in order to clarify the pathogenesis by means of I-123 or Tc-99m scintigraphy, with and without thyroid ultrasonography and serum thyroglobulin measurement. The patients were divided into two groups: sixteen neonates with hypothyroidism discovered in a neonatal mass screening program performed between 1985 and 1992 (group A), and eleven neonates discovered between 1992 and 1994 (group B). In group A, only I-123 scintigraphy was performed to determine the pathogenesis. Group B was subjected to Tc-99m scintigraphy, thyroid ultrasonography and serum thyroglobulin measurement. The pathogenesis of thirteen patients with congenital hypothyroidism in group A (1985-1992) were as follows; seven patients were diagnosed as having dysorganogenesis, consisting of six with ectopic glands and one with agenesis of the thyroid gland. Six patients were diagnosed as having dyshormonogenesis. All three patients with transient hypothyroidism were diagnosed as having transient dyshormonogenesis. The pathogenesis of eight patients with congenital hypothyroidism in group B (1992-1994) were as follows; one patient of dysorganogenesis with ectopic gland and seven patients of dyshormonogenesis consisting of one patient with iodine transport defect, one patient with iodine transport defect combined with ectopic gland, one patient with dyshormonogenesis combined with dysorganogenesis and four patients with only dyshormonogenesis. All of three patients with transient hypothyroidisms were diagnosed as transient dyshormonogenesis. These results suggest that the examination of thyroid scintigraphy and ultrasonography as well as serum thyroglobulin measurement are useful to clarify the etiology and pathogenesis of congenital hypothyroidism.