Intelligence of patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency, their parents and unaffected siblings.

IQ measurements were performed in 33 patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency (110.6 +/- 13.9), in 29 unaffected siblings (113.8 +/- 11.3) and in 48 parents (104.4 +/- 9.4). The results were significantly higher than normal in the patients and siblings, but not in the parents. They were also significantly higher in the patients and siblings as compared to the parents. It is concluded that neither pre- or postnatal androgen exposure nor a genetic linkage can be made responsible for the increased IQ in congenital adrenal hyperplasia, but that more likely methodological factors (such as outdated standards) account for the higher values in patients and siblings.