Iodide Transport Defect and Breast Milk Iodine

Area of Science:

• Endocrinology
• Genetics
• Pediatrics

Background:

• Iodide transport defect (ITD) is a congenital hypothyroidism resulting from mutations in the sodium/iodide symporter (NIS) gene.
• The NIS in the lactating mammary gland concentrates iodide, supplying iodine for infant thyroid hormone synthesis via breast milk.

Purpose of the Study:

• To investigate the impact of a specific NIS gene mutation (T354P) on maternal iodide transport and its implications for infant nutrition.
• To evaluate the efficacy of prophylactic iodine supplementation in breastfed infants of mothers with ITD.

Main Methods:

• Case study of a 34-year-old Japanese woman with ITD (homozygous NIS T354P mutation) treated for hypothyroidism.
• Monitoring of breast milk iodine concentration before and after daily potassium iodide supplementation (50 mg) initiated postpartum.
• Assessment of infant thyroid function from birth to 6 months of age.

Main Results:

• Maternal breast milk iodine concentration increased from 54 µg/l to 90 µg/l with daily supplementation.
• The infant's thyroid function remained normal throughout the 6-month follow-up period.
• The infant was weaned to iodine-rich formula after 6 weeks of breastfeeding.

Conclusions:

• Infants breastfed by mothers with ITD are at risk of iodine deficiency.
• Prophylactic iodine supplementation for these infants is crucial to prevent severe iodine deficiency and support normal thyroid development.