Congenital hypothyroidism is a condition where a newborn has decreased or absent thyroid function and thyroid hormone production. It is the most common cause of preventable mental retardation and its early diagnosis can only be achieved through systematic neonatal screening because its clinical manifestations are usually late. The etiologic study of this condition relies heavily on nuclear medicine and ultrasound, describing various findings. This research analyzed the characteristics of the ultrasound patterns observed in these children and their correlation with the most common etiologies. The use of ultrasound allows selecting children that require scintigraphic studies, decreasing the use of radiation in neonates.