What deficiency is most commonly linked to congenital adrenal hyperplasia (CAH)?

Congenital adrenal hyperplasia (CAH) most commonly arises due to a deficiency in the enzyme 21-hydroxylase. This deficiency impacts the adrenal gland's ability to convert progesterone and 17-hydroxyprogesterone into cortisol and aldosterone, leading to an accumulation of steroid precursors. The lack of cortisol triggers increased production of adrenocorticotropic hormone (ACTH) by the pituitary gland, which further stimulates adrenal steroidogenesis and can result in adrenal hyperplasia.

In cases of 21-hydroxylase deficiency, individuals can present with a range of symptoms depending on the degree of enzyme activity. Classic forms can lead to significant cortisol and aldosterone deficiency, resulting in adrenal crisis, salt-wasting, and ambiguous genitalia in females due to excess androgen production. Non-classic forms may present later in life with milder symptoms like hirsutism or menstrual irregularities.

Other enzyme deficiencies associated with CAH include 11-hydroxylase deficiency, 17-alpha hydroxylase deficiency, and 3-beta hydroxysteroid dehydrogenase deficiency, but these occur less frequently. Each of these alternatives affects corticosteroid and sex hormone production differently and leads to distinct clinical presentations, making