Congenital Adrenal Hyperplasia (CAH)

Congenital Adrenal Hyperplasia (CAH) is the most prevalent cause of intersex among people with XX chromosomes. About 1 in 10,000 to 18,000 children are born with congenital adrenal hyperplasia, but it does not cause intersex in those with XY chromosomes, so the prevalence of CAH-related intersex is about 1 in 20,000 to 1 in 36,000.

Among the many causes of intersex, only CAH represents a real medical emergency in the newborn period. Click here to read about the medical risks of CAH both at birth and later in life.

CAH occurs when there is a broken genetic “recipe” for making cortisone in the adrenal glands (the glands on top of the kidneys that make various hormones and add them to the blood stream). Because the recipe is broken, the adrenal glands, while trying to make cortisone, may make an unusually high level of other hormones that are “virilizing”. That is, they can make XX embryos have larger than average clitorises, or even a clitoris that looks rather like a penis, or labia that look like a scrotum.

To be more specific, intersex occurs in relation to CAH when an anomaly of the adrenal function causes the synthesis and excretion of an androgen precursor, initiating virilization of a XX person in-utero.

Because the virilization originates metabolically, masculinizing effects continue after birth. So CAH can cause the person to develop masculine-typical characteristics like dense body hair, a receding hairline, deep voice, prominent muscles, etc. Sex phenotype varies along the full continuum, with the possible added complication of metabolic problems which upset serum sodium balance.

The metabolic effects of CAH can be counteracted with cortisone. The long term use of cortisone itself produces significant dependence and other side effects, all of which need to be explained honestly and openly.

CAH also occurs in XY individuals, and requires medical attention as it has significant impacts on health, but it does not cause ambiguous genitalia. CAH doesn’t cause intersex in XY individuals because their testes already produce so much testosterone that the added virilizing hormones don’t really make a difference. However, untreated CAH can cause boys to have their puberty earlier than other boys. This can be a problem because it will stop them from growing taller (so they end up as very short adults) and because it can cause them to be very sexual well before other children their age are having such strong sexual thoughts and desires.