title: Timing of vulnerability of the brain to iodine deficiency in endemic cretinism.
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.
authors.affiliation: Xinjiang Anti-Epidemic and Health Station, Urumchi.
authors.forename: X Y
authors.initials: XY
authors.lastname: Cao
authors.forename: X M
authors.initials: XM
authors.lastname: Jiang
authors.forename: Z H
authors.initials: ZH
authors.lastname: Dou
authors.forename: M A
authors.initials: MA
authors.lastname: Rakeman
authors.forename: M L
authors.initials: ML
authors.lastname: Zhang
authors.forename: K
authors.initials: K
authors.lastname: O'Donnell
authors.forename: T
authors.initials: T
authors.lastname: Ma
authors.forename: K
authors.initials: K
authors.lastname: Amette
authors.forename: N
authors.initials: N
authors.lastname: DeLong
authors.forename: G R
authors.initials: GR
authors.lastname: DeLong
mesh_terms: D001921:Brain / Q000187:drug effects / Q000196:embryology*; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D003409:Congenital Hypothyroidism / Q000517:prevention & control*; D005314:Embryonic and Fetal Development / Q000187:drug effects; D005260:Female; D005315:Fetal Diseases / Q000517:prevention & control; D005333:Fetus / Q000187:drug effects / Q000502:physiology; D006257:Head / Q000033:anatomy & histology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007455:Iodine / Q000172:deficiency* / Q000627:therapeutic use*; D009460:Neurologic Examination; D011247:Pregnancy; D011248:Pregnancy Complications / Q000188:drug therapy*; D011262:Pregnancy Trimester, Second
chemical_list: D007455:Iodine