Congenital Adrenal Hyperplasia

Question 1

Pathology

Answer 1

Congenital adrenal hyperplasia is caused by a congenital deficiency of the 21-hydroxylase enzyme.

This causes UNDERPRODUCTION OF CORTISOL AND ALDOSTERONE and so RAISED ACTH due to negative feedback causing an OVERPRODUCTION of ANDROGENS

Question 2

Inheritance

Answer 2

Autosomal recessive

Question 3

Clinical Features

Answer 3

HIGH ANDOGREN:

• Female patients: presents at birth with virilised genitalia, known as “ambiguous genitalia” and an enlarged clitoris due to the high testosterone levels.
• Male: precocious puberty

LOW ALDOSTERONE:

• hyponatraemia
• hyperkalaemia

LOW CORTISOL:
- Low glucose

This leads to signs and symptoms:
Poor feeding
Vomiting
Dehydration
Arrhythmias

HIGH ACTH:
- Skin hyperpigmentation

Question 4

Investigations

Answer 4

U+Es: hyperkalaemia, hyponatraemia

Enzyme levels: low

ACTH stimulation: An IV injection of 250 micrograms of ACTH is given. 17-hydroxyprogesterone levels are measured at baseline and then 60 minutes later: CAH = significant increased levels

Genetic Testing

Question 5

Management

Answer 5

Cortisol replacement: usually with hydrocortisone

Aldosterone replacement: usually with fludrocortisone

Female patients with “virilised” genitals may require corrective surgery