Transient Congenital Hypothyroidism after Topical Iodine in Pregnancy and Lactation

Abstract

Congenital goiter and (rarely) transient hypothyroidism have been reported to occur sporadically in infants whose mothers received iodides during pregnancy. The present authors report a case of prolonged but transient hypothyroidism without goiter in a girt whose mother used povi-done iodine preparations during pregnancy and lactation. A 6-week-old Jewish girl of Ashkenazi origin, the youngest of five healthy siblings, was referred to the authors' unit because of a low serum total thyroxine concentration of 3 μg/dl (normal value, more than 7 μg/dl), revealed by routine screening for congenital hypothyroidism. She was born at term after an uneventful pregnancy and delivery. Her birth weight was 4000 gm. During the pregnancy, the mother washed herself almost daily with a solution of povidone iodine, a complex of iodine and polyvinylpyrrolidone which releases free iodine in solution, with 1 per cent available iodine. She had also rubbed large areas of her skin with povidone iodine ointment (1 per cent) because of spreading furunculosis. These practices were continued during lactation until referral. The mother's aunt and uncle suffered from a thyroid disorder, the nature of which could not be determined. Physical examination revealed an infant in good condition, with mild jaundice. Her weight was 5.1 kg, her length was 54.5 cm, and her head circumference was 40 cm. Body temperature was normal. No goiter was palpable. The face was round, with a protruding tongue. Respiration was noisy, but there was no sign of respiratory distress. The abdomen was large, and the liver was palpated 3 cm below the costal margin. A large umbilical hernia was present. A neurological examination yielded normal results, except for moderately delayed deep tendon reflexes. Laboratory tests disclosed a free thyroxine serum concentration of 0.4 ng/dl (normal values, 0.7–2 ng/dl). Thyroid-stimulating hormone (TSH) was 99 μU/ml (normal values, 0.8–5 μU/ml). Indirect bilirubin was 95 μmol/liter. Thyroid antibodies were negative in the child and her mother. A thyroid scan yielded normal results. A diagnosis of primary hypothyroidism was made on the basis of raised TSH and decreased thyroxine concentrations, and treatment with t-thyroxine sodium was started. On follow-up, there was an increase in thyroxine and a decrease in TSH concentrations (Table 1). Growth and psychomotor development were normal, and treatment was stopped at the age of 7 months. At 1 year, growth and development were normal.