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Original Article
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Volume 331:1739-1744 December 29, 1994 Number 26
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Timing of Vulnerability of the Brain to Iodine Deficiency in Endemic Cretinism
Xue-Yi Cao, Xin-Min Jiang, Zhi-Hong Dou, Murdon Abdul Rakeman, Ming-Li Zhang, Karen O'Donnell, Tai Ma, Kareem Amette, Nancy DeLong, and G. Robert DeLong

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ABSTRACT

Background Endemic cretinism, caused by severe iodine deficiency during pregnancy, is the world's most common preventable cause of mental retardation. It can be prevented by iodine treatment before conception, but whether it can be prevented or ameliorated by treatment during pregnancy or after delivery is not known.

Methods In a severely iodine-deficient area of the Xinjiang region of China, we systematically administered iodine to groups of children from birth to three years of age (n=689) and women at each trimester of pregnancy (n=295); we then followed the treated children and the babies born to the treated women for two years. We used three independent measures of neural development: the results of the neurologic examination, the head circumference (which correlates with brain weight in the first postnatal year), and indexes of cognitive and motor development. Untreated children one to three years of age, who were studied when first seen, served as control subjects.

Results The prevalence of moderate or severe neurologic abnormalities among the 120 infants whose mothers received iodine in the first or second trimester was 2 percent, as compared with 9 percent among the 752 infants who received iodine during the third trimester (through the treatment of their mothers) or after birth (P=0.008). The prevalence of microcephaly (defined as a head circumference more than 3 SD below U.S. norms) decreased from 27 percent in the untreated children to 11 percent in the treated children (P=0.006), and the mean ( ±SD) developmental quotient at two years of age increased (90 ±14, vs. 75 ±18 in the untreated children; P<0.001). Treatment in the third trimester of pregnancy or after delivery did not improve neurologic status, but head growth and developmental quotients improved slightly. Treatment during the first trimester, which was technically problematic, improved the neurologic outcome.

Conclusions Up to the end of the second trimester, iodine treatment protects the fetal brain from the effects of iodine deficiency. Treatment later in pregnancy or after delivery may improve brain growth and developmental achievement slightly, but it does not improve neurologic status.


Source Information

From the Xinjiang Anti-Epidemic and Health Station, Urumchi (C.X.-Y., D.Z.-H., M.A.R.); the Institute of Endemic Diseases Research, Urumchi (J.X.-M., Z.M.-L., K.A.); and Tianjin Medical College, Tianjin (M.T.) -- all in China; and Duke University Medical Center, Durham, N.C. (K.O., N.D., G.R.D.).

Address reprint requests to Dr. DeLong at the Division of Pediatric Neurology, Duke University Medical Center, Box 3936, Durham, NC 27710.

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