These results imply that the defect causing the hypogonadotropic hypogonadism seen in 4H leukodystrophy is at the level of the pituitary, potentially due to abnormal small RNA synthesis, resulting in defective transcription of key mediators required for the function of the GnRH receptor protein, or for gonadotropin synthesis. The gene discussed is GNRHR; the disease is hypogonadotropic hypogonadism.