Early Identification of Primary Hypothyroidism in Neonates Exposed to Intra-Lymphatic Iodinated Contrast: A Case Series.

Context: In neonates, iatrogenic hypothyroidism can result from topical or IV iodine exposure. Data on intralymphatic iodine exposure, risk factors for disease severity, and timing of hypothyroidism are limited. Case Descriptions: We report 4 cases of premature neonates with previously normal thyroid function tests (TFTs) who developed hypothyroidism after intralymphatic iodinated contrast. Patients 1 and 2, premature infants with complex medical histories, had chylous effusions and high-volume chest tube output requiring imaging with lymphangiograms on day of life (DOL) 97 and DOL 43, respectively. They developed severe, primary hypothyroidism with TSH of 335.7 mIU/mL (reference range, 1.7 to 9.1) on DOL 111 and TSH of 470.2 mIU/mL (reference range, 1.7 to 9.1) on DOL 68. Patient 3 had prenatally diagnosed fetal hydrops manifesting with chylous effusions and high-volume chest tube output. The infant underwent lymphangiography on DOL 90 and was noted to have an elevated TSH of 13.35 mIU/mL (reference range, 1.7 to 9.1) 4 days later with spot urine iodine of 1742 mu g/L (normal, <200). Patient 4 had a lymphatic malformation and underwent sclerotherapy with doxycycline with intralymphatic iodine exposure on DOL 4 and was found to haveaTSHof16.7mU/mL (reference range, 1.7 to 9.1) 3 days later with spot urine iodine of 228,712 mu g/L (normal, <200). The TFT results for all patients improved after levothyroxine administration. Conclusion: Intralymphatic iodine should be considered a major risk factor in the development of iatrogenic primary hypothyroidism, especially in premature neonates soon after exposure. Close monitoring of TFTs is imperative to avoid potential long-term adverse outcomes in this population.