Primary adrenal insufficiency (PAI) including congenital adrenal hyperplasia (CAH), X-linked adrenal hypoplasia congenita (X-AHC) and Xp21 contiguous gene deletion syndrome, are conditions characterized by a failure to produce cortisol and it is the most common etiology of Ald synthesis defects. Here, ABCD1 is linked to congenital adrenal hyperplasia.