Congenital adrenal hyperplasia (CAH)

Congenital adrenal hyperplasia (CAH) is caused by an adrenal gland disorder whereby synthesis of cortisol is affected by an enzyme defect. The defect leads to an accumulation of androgen precursors in the blood, with results varying between salt-wasting, high blood pressure (hypertensive), virilising, or feminising.

Congenital adrenal hyperplasia is caused by a mutation in a gene, and most defects result in either excessive or deficient sex hormone production, affecting the development of primary or secondary sex characteristics in babies, children or adults.

Congenital adrenal hyperplasia is considered a cause of Differences of Sexual Development (DSD).

Deficient mineralocorticoids

Deficiencies in mineralocorticoids leave an infant with salt wasting that can lead to dehydration and death.

Excess androgens

Too much of these sex hormones, and you end up with:

• A functional and average-sized penis, but no sperm
• Variations in genitalia, usually in females, with difficulty in determining sex/gender
• Early pubic hair and fast growth in childhood
• Precocious puberty or the complete failure of puberty
• Excessive facial hair
• Virilisation
• Menstrual irregularity in teen years
• Infertility (caused by lack of ovulation)
• An enlarged clitoris (clitoromegaly)
• A shallow or closed-ended vagina (vaginal atresia)

How congenital adrenal hyperplasia works

Normal endocrine function is set about by cortisol production, with production starting in the second month in the womb. Most congenital adrenal hyperplasia is characterised by low cortisol production, which results in high levels of ACTH.

This increase leads to hyperplasia – overgrowth – and overactivity of steroid-producing cells in the adrenal cortex, with this being present at birth (congenital).

Congenital adrenal hyperplasia is caused by a recessive gene, meaning that both the mother and the father of a baby must be recessive carriers for the child to carry CAH genes.

Couples with the gene can use various fertility and genetic testing to avoid the gene in their offspring. Every child in most western countries is screened for congenital adrenal hyperplasia at birth, and if detected early enough, the child can live a happy life with early intervention.

How congenital adrenal hyperplasia affects an individual

Each person will have their own version of congenital adrenal hyperplasia, and it will affect each individual differently. The cortisol deficiency is likely to not be the worst problem affecting those with CAH, with the production of androgens and oestrogens posing a greater set of issues.

The very mildest form affects ovulation and fertility in adults, but the worst types are associated with multiple enzymatic inefficiencies that cause foetal changes and issues in the womb and shortly after.

Treatment for congenital adrenal hyperplasia

Since it is a genetic issue, CAH treatment focuses on treating the symptoms and trying to re-regulate or mimic normal hormone systems. Some treatments may include all or any of the following:

• Supplementation with glucocorticoid to reduce hyperplasia (overgrowth) and overproduction of androgens and mineralocorticoids.
• Replacing mineralocorticoid and salt if deficient.
• Replacing hormones (testosterone, oestrogen) at puberty if deficient.
• Different hormone therapies to optimise growth (delay puberty or delaying bone maturation).

This condition has forced a lot of difficult discussions, including extensive debates over genital reconstructive surgery, gender assignment of severely affected XX infants, and how to treat this condition before birth.

References

• Al-Maghribi H. Congenital adrenal hyperplasia: problems with developmental anomalies of the external genitalia and sex assignment. Saudi J Kidney Dis Transpl. 2007 Sep. 18(3):405-13. [Medline].