What is 17-Hydroxylase Deficiency?

17-Hydroxylase deficiency is a very rare cause of CAH. The diagnosis is usually made at puberty with the clinical findings of:

• Hypertension (high blood pressure)
• Hypokalaemia (low blood potassium levels)
• Hypogonadism (low production of sex steroids)

The deficiency of this enzyme will result in a reduction in the conversion of pregnenolone and progesterone into 17-Hydroxypregnenolone and 17-Hydroxyprogesterone respectively (see the diagram in the 'What is Congenital Adrenal Hyperplasia' section). The deficiency will result in an accumulation of aldosterone, explaining the hypertension and hypokalaemia (see physiology section), and a deficiency of cortisol and sex steroids.

The diagnosis of 17-Hydroxylase deficiency is made by demonstrating the accumulation of hormones prior to this enzyme deficient step. The basis of the treatment is to administer glucocorticoids (to suppress the ACTH production) and to manage the aldosterone excess. Gonadal steroids are also given at puberty. Most patients are raised as females regardless of whether they are genetically male or female. The deficient enzyme will prevent the production of virilising sex hormones during development.