In congenital adrenal hyperplasia, which deficiency is primarily implicated?

In congenital adrenal hyperplasia (CAH), the primary deficiency implicated is that of 21-hydroxylase. This enzyme plays a critical role in the adrenal steroidogenesis pathway, particularly in the synthesis of cortisol and aldosterone.

When 21-hydroxylase is deficient, the conversion of 17-hydroxyprogesterone to 11-deoxycortisol is impaired, and the conversion of progesterone to 11-deoxycorticosterone is also disrupted. As a result, there is a decreased production of both cortisol and aldosterone, leading to an accumulation of 17-hydroxyprogesterone and ultimately causing adrenal hyperplasia due to unopposed adrenal stimulation by ACTH.

The lack of cortisol production can lead to adrenal crisis, hypotension, and electrolyte imbalances, particularly hyperkalemia and hyponatremia. In female patients, the excess androgens produced due to shunting in steroidogenesis can lead to virilization and ambiguous genitalia.

The other deficiencies mentioned (17-hydroxylase, 11-hydroxylase, and 3-beta-hydroxysteroid dehydrogenase) involve various other defects in steroidogenesis, which cause different clinical