Iodide Transport Defect and Breast Milk Iodine

Background: Iodide transport defect (ITD) is a dyshormonogenetic congenital hypothyroidism caused by sodium/iodide symporter (NIS) gene mutations. In the lactating mammary gland, iodide is concentrated by NIS, and iodine for thyroid hormone synthesis is thereby supplied to the infant in the breast milk. Case Description: A 34-year-old Japanese woman was diagnosed with ITD caused by a homozygous NIS gene mutation T354P. She had begun treatment of primary hypothyroidism with levothyroxine at the age of 5. She Received: March 4, 2016 Accepted after revision: April 26, 2016 Published online: May 27, 2016 Tetsuya Mizokami, MD Tajiri Thyroid Clinic 2-6-3 Suizenji Kumamoto 862-0950 (Japan) E-Mail tetsuyamizokami @ hotmail.com © 2016 European Thyroid Association Published by S. Karger AG, Basel 2235–0640/16/0052–0145$39.50/0 www.karger.com/etj What Is Known about This Topic? • Iodide transport defect (ITD) is a dyshormonogenetic congenital hypothyroidism caused by sodium/ iodide symporter (NIS) gene mutations. In the lactating mammary gland, iodide is concentrated by NIS. What Does This Case Report Add? • The iodine concentration in an ITD patient’s breast milk is low. Possible iodine deficiency in the infant breast-fed by an ITD patient should be kept in mind.