Intellectual capacity of subjects exposed to methimazole or propylthiouracil in utero

Z. Eisenstein*, M. Weiss, Y. Katz, H. Bank

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


Antithyroid drugs, considered the treatment of choice for hyperthyroidism during pregnancy, may have an adverse effect on intellectual development of the offspring. We examined the intellectual capacity of 31 subjects aged 4-23 years, born to women with Graves disease who received antithyroid drugs throughout pregnancy. Methimazole 40-140 mg/week (n=15) or propylthiouracil 250-1400 mg/week (n=16) was given. I.Q. was assessed using the Wechsler test appropriate for age. Twenty-five unexposed siblings served as controls. The exposed and unexposed groups did not differ with respect to the total I.Q. Both groups scored equally in verbal and performance skills and in each of six main subcategories of the tests. There was no difference between exposure to methimazole and propylthiouracil or between the higher (>40 mg/week and >600 mg/week, respectively) and lower dosages. All children were euthyroid at birth and none had goitre. We conclude that exposure to methimazole or propylthiouracil during pregnancy in doses sufficient to control maternal hyperthyroidism does not pose any threat to intellectual capacity of the offspring.

Original languageEnglish
Pages (from-to)558-559
Number of pages2
JournalEuropean Journal of Pediatrics
Issue number8
StatePublished - Aug 1992


  • Intelligence tests
  • Methimazole
  • Prenatal exposure
  • Propylthiouracil


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