Congenital adrenal hyperplasia pathophysiology

Congenital adrenal hyperplasia main page
Overview
Classification 21-hydroxylase deficiency
11β-hydroxylase deficiency
17 alpha-hydroxylase deficiency
3 beta-hydroxysteroid dehydrogenase deficiency
Cytochrome P450-oxidoreductase (POR) deficiency (ORD)
Lipoid congenital adrenal hyperplasia
Differential Diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Pathophysiology

• Simple Virilizing Form

  • Female fetuses demonstrate evidence of androgen excess including genital ambiguity. Precocious puberty, accelerated growth followed by premature growth arrest due to epiphiseal fusion can be noted. Because virilization or androgen excess can be very mild, it can be overlooked until later in life.

• Salt-Wasting Form

  • These patients may have virilizing features but 2/3 will also manifest mineralocorticoid deficiency with salt wasting, hyperkalemia, and hypotension, usually within the first 2 weeks of life.

• Nonclassical Form

  • Patients may present with amenorrhea/oligomenorrhea with signs of androgen excess such as hirsutism. These women usually present around puberty and resemble patients with polycystic ovarian syndrome.

Genetics

All involved genes are autosomal. See the table under 'Biochemistry' subheading for chromosomal locations.

Because they code for enzymes with amplifiable activity, noticeable effects only occur in people with two defective alleles of thesegenes. Hundreds of different allelic mutations of these genes have been reported. Nearly always, each parent of an affected person is an unaffected heterozygote (i.e., asymptomatic carrier of one defective gene and one normal gene and has no ill effects). Each child of that pair of parents has a 25% chance of being affected, "having CAH". Prenatal diagnosis and heterozygote detection are now possible.

Although mutations leading to the various forms of CAH have been found all over the world, there are substantial differences in the carrier rates of specific abnormal alleles in different regions and ethnic groups.