Congenital Adrenal Hyperplasia

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Congenital adrenal hyperplasia (CAH) is the most common cause of ambiguous genitalia.




The Case of...

a simple case introducing clincial presentation and calling for a differential diagnosis. To get students thinking.

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Causes and Risk Factors

CAH is an autosomal-dominant condition leading to partial or total enzyme defect.

In over 95% of cases, 21-hydroxylase deficiency leads to decreased cortisol and aldosterone, leading to androgen overproduction.


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Cortisol deficiency increases ACTH production, leading to adrenal hyperplasia.

Different types include:

Late-onset 21-hydroxylase deficiency



Salt-wasting 21-hydroxylase deficiency

Salt-wasting accounts for over half of cases. It leads to low [Na], high [K], low [Cl], low glucose, and high ACTH.

It is a medical emergency, as infants can die of dehydration and shock at 2-4 weeks of age.

Treat with fluid and electrolytes, restore glucose, and start lifetime regimen of hydrocortisone.


Simple virilizing 21-hydroxylase deficiency


11-hydroxylase deficiency


17-hydroxylase deficiency



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Signs and Symptoms

Clinical presentation depends on specific deficieincy.

  • history
  • physical exam



Physical Exam

Salt-wasting 21-hydroxylase deficiency can lead to hyperpigmentation of genitals and areola.

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  • lab investigations
  • diagnostic imaging

Lab Investigations



Increased ACTH leads to increased:

  • 17-OH progesterone
  • testosterone, DHEAS
  • urinary 17-ketosteroids

Diagnostic Imaging

Advanced bone age results.

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Differential Diagnosis

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Stress dosing of cortisol

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Consequences and Course

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The Case of...

Case #2 - a small story wrapping it all up and asking about esp management.

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Additional Resources

SickKids Flash animation

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Topic Development




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