Context:The effects of maternal inorganic iodine therapy on infant thyroid function are not well known.Objective:This study investigated the effects on infant thyroid function of maternal inorganic iodine therapy when administered to lactating mothers with Graves disease.Design and Setting:This study was a prospective case series performed at the Tajiri Thyroid Clinic, Kumamoto, Japan.Participants:Subjects were 26 infants of lactating mothers with Graves disease treated with potassium iodide (KI) for postpartum thyrotoxicosis.Main Outcome Measures:Infant blood levels of thyroid-stimulating hormone (TSH) and free thyroxine were measured using the dried filter-paper method. Iodine concentrations in breast milk and infant urine were measured on the same day. Subclinical hypothyroidism was defined as a blood TSH level of ≥10 or ≥5 μIU/mL in <6-month-old and 6- to 12-month-old infants, respectively.Results:The median age of the infants was 3 months (range, 0 to 10 months). The median KI dose was 50 mg/d (range, 10 to 100 mg/d). High median iodine concentrations were detected in breast milk (15,050 μg/L; range, 831 to 72,000 μg/L) and infant urine (15,650 μg/L; range, 157 to 250,000 μg/L). Twenty-five of 26 infants had normal thyroid function. Although one infant had subclinical hypothyroidism (blood TSH, 12.3 μIU/mL), the TSH level normalized to 2.3 μIU/mL at 2 months after KI discontinuation.Conclusion:In Japan, where iodine intake is sufficient, administration of inorganic iodine to lactating mothers with Graves disease did not affect thyroid function in most infants despite high levels of exposure to iodine via breast milk.

We herein experienced 9 patients with primary thyroid lymphoma that developed during 3-18 years of ultrasonographic follow-up of Hashimoto's thyroiditis. All nine patients had localized mucosa-associated lymphoid tissue (MALT) lymphoma. Two patients had diffuse type, one had mixed type, and six had nodular type according to the ultrasonographic classification. A clearly enlarging goiter was observed before the diagnosis of lymphoma in 3 patients. An enlarging goiter was not apparent in the remaining 6 patients with nodular type lymphoma, however, the emergence or enlargement of a hypoechoic nodular lesion was observed. Thyroid MALT lymphoma may be diagnosed early by an ultrasonographic follow-up of Hashimoto's thyroiditis.

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 delivered a baby at the age of 36. The iodine concentration in her breast milk was 54 µg/l. She took a 50-mg potassium iodide tablet daily to supply iodine in the breast milk, starting on the 5th day postpartum. Her breast milk iodine concentration increased to 90 µg/l (slightly above the minimum requirement level). The patient weaned her baby and stopped taking the daily potassium iodide tablet 6 weeks postpartum, and the baby began to be fed with relatively iodine-rich formula milk. The baby's thyroid function remained normal from birth until 6 months of age. Conclusion: Possible iodine deficiency in the infant breast-fed by an ITD patient should be kept in mind. Prophylactic iodine supplementation is essential for such infants in order to prevent severe iodine deficiency.

Context We previously reported that inorganic iodine therapy in lactating women with Graves disease (GD) did not affect the thyroid function in 25 of 26 infants despite their exposure to excess iodine via breast milk. Objective To further assess thyroid function in infants nursed by mothers with GD treated with inorganic iodine. Design Case series Setting Tajiri Thyroid Clinic, Japan Participants One hundred infants of lactating mothers with GD treated with potassium iodide (KI) for thyrotoxicosis Main Outcome Measures Infant blood thyrotropin (TSH) and free thyroxine (FT4) levels were measured by the filter-paper method. Subclinical hypothyroidism was defined as TSH ≥10 μIU/mL and ≥5 μIU/mL in infants aged &lt;6 and ≥6 months, respectively. Results Overall, 210 blood samples were obtained from 100 infants. The median infant age was 5 (range, 0-23) months; median maternal KI dose, 50 (4-100) mg/day; median blood TSH level, 2.7 (0.1&gt; -12.3) μIU/mL; and median blood FT4 level, 1.04 (0.58-1.94) ng/dL. Blood TSH level was normal in 88/100 infants. Twelve infants had subclinical hypothyroidism; among them, blood TSH levels normalized after maternal KI withdrawal or stopping breastfeeding in three infants. In seven infants, blood TSH levels normalized during KI administration without stopping breastfeeding. Two infants could not be followed up. Conclusions In Japan, inorganic iodine therapy for lactating women with GD did not affect thyroid function in most of the infants. Approximately 10% of infants had mild subclinical hypothyroidism, but blood TSH level normalized during continued or after discontinuing iodine exposure in all followed up infants.

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