POMC and classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency: It is caused by certain enzyme deficiencies, mostly 21 hydroxylase deficiency (in more than 90% of cases), affecting steroidogenesis and reduced cortisol production by adrenals that leads to overstimulation of adrenal glands by adrenocorticotropic hormone (ACTH) through feedback mechanism leading to its hyperplasia and results in excessive testosterone production.