Congenital Adrenal Hyperplasia (CAH) occurs due to deficiency of one or the other enzyme in the common adrenal cortical  hormone bio synthetic pathway.

Depending on the enzyme which is deficient, there is less production of the hormone along that pathway but the excess substrate thus produced is redirected to other pathways leading to excess production along those pathways.

The three common enzyme deficiencies and their effects are as following:
1) 21 β hydroxylase deficiency: ↓ MC & GC while ↑ SS (virilisation)
2) 11 β hydroxylase deficiency: ↓ GC while ↑ MC &  SS (virilisation + hypertension)
3) 17α  hydroxylase deficiency: ↓ GC & SS while ↑ MC (hypertension)

where, GC = Glucocorticoides, MC = mineralocorticoides, SS = sex steroides.

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if GC = 1, MC = 2 & SS = 7


1) 21 β hydroxylase deficiency: ↓ 2 & 1 while ↑ 7
2) 11 β hydroxylase deficiency: ↓ 1 & 1 while ↑ 2 & 7
3) 17α  hydroxylase deficiency: ↓ 1 & 7 while ↑ 2