TRANSIENT IODINE ORGANIFICATION DEFECT IN INFANTS WITH ECTOPIC THYROID-GLANDS

Background: Thyroid gland ectopy is the most common cause in infants w ith congenital hypothyroidism (CH). Its association with iodine organi fication defect, as suggested by positive perchlorate discharge test ( PDT) has been reported. However, whether such an association represent s a true or transient defect has not yet been determined. This finding has an important clinical, epidemiological, and genetic implications. Objective: To determine the natural history of iodine organification defect in patients with CH caused by thyroid ectopy detected by neonat al screening. Design: Prospective longitudinal study. Setting: King Kh alid University Hospital, Riyadh, Saudi Arabia. Patients and Methods: PDT was performed, at the time of diagnosis and follow-up, in infants who showed an enlarged ectopic thyroid gland with a Tc-99m pertechneta te uptake of 2% or more. Results: Of 115 neonates with ectopic thyroid glands, 19 showed an enlarged gland with Tc-99m uptake ranging from 2 to 3.2%. Perchlorate discharge test was performed in 13 of these and was consistent with iodine organification defect in nine. Repeated PDT in seven patients showed normal values. Conclusion: The results of th e authors' study indicate the transient nature of the iodine organific ation defect and suggest that a delay in the developmental of syntheti c mechanisms occur in the dysgenetic glands.