Clinical and laboratory features of children and adolescents with congenital hypothyroidism due to dyshormonogenesis in southern Brazil

objective: to characterize the phenotype of patients with congenital hypothyroidism (ch) due to dyshormonogenesis, and to hypothesize on the degree of genetic defect. subjects and methods: patients with dyshormonogenesis were subdivided into g1 (radioactive iodine uptake, raiu > 15%; n = 62) and g2 (raiu < 15%; n = 32). thyroglobulin (tg) was measured in all patients; perchlorate discharge test (pdt) was performed in g1; and saliva-to-plasma radioiodine ratio (i- s/p) in g2. results: levels of tsh, tt4, and ft4 before treatment and upon diagnosis confirmation were significantly different in both groups, but not between groups. in g1, 27 patients developed goiter; 17 had positive pdt (14%-71% discharge), 11 had tg < 2.5 ng/dl (one with high tsh), and one developed thyroid carcinoma. in g2, four patients developed goiter, and three had low i- s/p. conclusion: these data suggest an iodide organification defect in 17 cases; an iodide transport defect (nis defect) in three, probable tsh resistance in 10, and a tg synthesis defect in two cases.