ckl,

"Hyper" means "too MUCH." "Hypo" means "too LITTLE."

In the case of Congenital Adrenal HYPERplasia, the adrenal glands become enlarged over time because they make too MANY male hormones(called "androgens"). This occurs because the adrenal glands are frustrated in their attempt to make cortisol, so compensate by over-producing androgens.

In the case of Congenital Adrenal HYPOplasia, the adrenal glands become shrunken over time, because they produce too few of ALL the adrenal hormones, including androgens.

So, the biggest difference between them is that adrenal hyperplasia involves too MUCH male hormone, while adrenal hypoplasia involves too LITTLE male hormone.

In early years, treatment is essentially the same, no matter which you have...i.e. cortisol replacement (hydrocortisone, prednisone, or dexamthasone) plus fludrocortisone. These medications replace missing cortisol and aldosterone (the salt-retaining hormone.)

Later in life, treatment to address sexual development might differ. Those with "HYPERplasia" might end up with treatment to slow down puberty (because they produce too many sex hormones naturally), while those with "HYPOplasia" might end up with treatment to speed it up (because they produce too few sex hormones naturally). Again, the production of sex hormones is the heart of the difference between the two.