Congenital adrenal hyperplasia (CAH) refers to a group of autosomal recessive disorders caused by congenital defects in specific enzymes involved in the biosynthesis of adrenal cortical hormones, leading to insufficient production of these hormones. The deficiency in adrenal hormone synthesis weakens the negative feedback inhibition on the hypothalamic-pituitary-adrenal axis, resulting in excessive secretion of ACTH. This causes adrenal cortical hyperplasia and accumulation of precursor substances upstream of the defective enzyme. The clinical and biochemical manifestations depend on the type and severity of the enzyme deficiency, which may include alterations in the levels of glucocorticoids, mineralocorticoids, and sex hormones, as well as the resulting clinical symptoms, signs, and biochemical abnormalities.
The most common types of CAH include 21-hydroxylase deficiency (21-OHD), 11β-hydroxylase deficiency (11β-OHD), 3β-hydroxysteroid dehydrogenase (3β-HSD) deficiency, 17α-hydroxylase deficiency (17α-OHD), cholesterol side-chain cleavage enzyme (P450scc) deficiency, and steroidogenic acute regulatory protein (StAR) deficiency. Among these, 21-OHD accounts for over 90% of cases, followed by 11β-OHD, which accounts for 5–8% of cases, while other types are rare.
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