Hypothalamic dysfunction is common in X-linked lissencephaly with abnormal genitalia; the authors are only aware of one other X-linked lissencephaly with abnormal genitalia case with documented hypothyroidism.7 Adrenal gland hypoplasia, however, has been identified at autopsy.4 Mutations in Arx block Leydig cell differentiation, leading to severely dysgenetic testicles,3 which do not respond in a functionally appropriate manner to hormone stimulation.11 This, rather than hypothalamic dysfunction, is thought to account for the genital phenotype. This evidence concerns the gene ARX and hypothyroidism.