Yet, the serum concentration of testosterone may also be within or above the normal range, and since the testosterone concentration reflects a combination of both testicular and adrenal derivation, and the concentration of LH to some degree may indicate whether an overproduction of adrenal-derived testosterone is present, the evaluation of Leydig cell function in male patients with CAH is challenging. This evidence concerns the gene PLOD1 and congenital adrenal hyperplasia.