Congenital Adrenal Hyperplasia (CAH)

This is due to a congenital 21-hydroxylase deficiency; an enzyme that converts progesterone → adrenal hormones.

Salt-wasting CAH

Complete deficiency of 21-hydroxylase

• Reduced cortisol and aldosterone → High ACTH in response, which leads to the adrenal hyperplasia

• The remaining progesterone is instead converted to testosterone

2-6 weeks after birth, huge volumes of sodium are lost and potassium is retained due to the low aldosterone (Salt water crisis). This leads to hypotension, dehydration, metabolic acidosis, and vomiting. This is a lethal form of CAH.

These symptoms don't present at birth as the foetus has a maternal supply of aldosterone via the foetus. The symptoms are solely due to the low aldosterone, and the maternal supply eventually runs out once the baby is born.

Virilising CAH

Partial deficiency of 21-hydroxylase

• As the deficiency isn't complete, there's therefore still some 21-hydroxylase activity and subsequent aldosterone production

• With some aldosterone, the features of salt-wasting aren't present

Presentation

• Ambiguous genitalia and an enlarged clitoris

• Virilisation - symptoms related to high androgen levels e.g. tall for age, facial hair, absent periods, deep voice, early pubarche

• Salt-wasting crises – Hyponatraemia, Hyperkalaemia, Hypoglycaemia

• Precocious puberty

• Vomiting

• Skin hyperpigmentation – due to increased ACTH in response to low cortisol

Management

• Hydrocortisone and Fludrocortisone for steroid replacement