Influence on psychological development of early treatment of congenital hypothyroidism detected by neonatal screening: a controlled study.

It has been shown that early diagnosis and treatment of congenital hypothyroidism based on neonatal screening will improve outcome. To test this hypothesis, we performed standard psychological tests (Gesell, Stanford-Binet, or Wechsler) in three groups of children with treated hypothyroidism: 14 were discovered by neonatal screening and 24 (15 with thyroid agenesis and 9 with ectopic thyroid) were diagnosed prior to institution of screening. Age (weeks) at initial treatment differed among the three groups (mean values +/- SE: screened 4.6 +/- 0.8, thyroid agenesis 19.3 +/- 4.0, ectopic thyroid 46.4 +/- 8.0). Age at testing averaged 3.3 years in all three groups. The global developmental quotient (DQ) or IQ score was lowest in the thyroid agenesis group (82 +/- 6, range 52 to 142), intermediate in the ectopic thyroid group (93 +/- 10, range 56 to 141) and highest in the screening group (104 +/- 4, range 75 to 127). Neonatal screening for congenital hypothyroidism results in earlier diagnosis than does use of the clinical criteria, and the consequent early treatment results in improved psychomental development.