title: Individualized treatment to optimize eventual cognitive outcome in congenital hypothyroidism.
abstract: In congenital hypothyroidism (CH), age-specific reference ranges (asRR) for fT4and thyrotropine (TSH) are usually used to signal over/under-treatment. We compared the consequences of individual fT4steady-state concentrations (SSC's) and asRR regarding over-treatment signaling and intelligence quotient at 11 y (IQ11) and the effect of early over-treatment with high L-T4dosages on IQ11.
  
  
  
  Sixty-one patients (27 severe, 34 mild CH) were psychologically tested at 1.8, 6, and 11 y. Development scores were related to over-treatment in the period 0-24 mo, relative to either individual fT4SSC's or asRR. Three groups were formed, based on severity of over/under-treatment 0-5 mo (severe, mild, and no over/under-treatment).
  
  
  
  FT4and TSH asRR missed 41-50% of the over-treatment episodes and consequently 22% of the over-treated patients, classified as such by fT4SSC's. Severe over-treatment 0-5 mo led to lowered IQ11's and to a 5.5-fold higher risk of IQ11< 85 than other treatment regimes. Under-treatment had no effect on development scores. Initial L-T4dosages >10 µg/kg resulted in a 3.7-fold higher risk of over-treatment than lower dosages.
  
  
  
  Data suggest that asRR, compared to fT4SSC's, signal over-treatment insufficiently. Using fT4SSC's and avoiding over-treatment may optimize cognitive outcome. Lowered IQ11's are usually a late complication of severe early over-treatment.
authors: Department of Pediatrics, Sophia Children's Hospital Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands.
authors: Jacoba J
authors: JJ
authors: Bongers-Schokking
authors: Department of Developmental and Educational Psychology, Faculty of Social Sciences, University of Leiden, Leiden, the Netherlands.
authors: Wilma C M
authors: WC
authors: Resing
authors: Department of Pediatrics, Leiden University Medical Center, Leiden, the Netherlands.
authors: Wilma
authors: W
authors: Oostdijk
authors: Department of Clinical Chemistry, Division of Endocrinology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands.|Department of Internal Medicine, Division of Endocrinology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands.
authors: Yolanda B
authors: YB
authors: de Rijke
authors: Department of Pediatrics, Sophia Children's Hospital Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands.
authors: Sabine M P F
authors: SM
authors: de Muinck Keizer-Schrama
mesh_terms: D002648:Child; D002657:Child Development / Q000187:drug effects; D002675:Child, Preschool; D003071:Cognition / Q000187:drug effects*; D003409:Congenital Hypothyroidism / Q000097:blood / Q000188:drug therapy* / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D000069342:Medical Overuse; D057285:Precision Medicine; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D013972:Thyrotropin; D013974:Thyroxine