Congenital Adrenal Hyperplasia (CAH) is a genetic disorder which causes an enzyme deficiency in the steroid pathway.  CAH caused by the 21-Hydroxylase enzyme deficiency, accounts for approximately 90-95% of all CAH disorders and the mutation arises on chromosome six.  Other rarer mutations of CAH arise on different chromosomes and exhibit some different features.

Specifically, CAH results in 3 disturbances:

• Lack of Cortisol
• Lack of Aldosterone
• Too much Androgen

Cortisol - which plays an important role in the bodies response to illness or injury by boosting blood sugar and blood pressure, thereby aiding recovery.

Aldosterone (salt-retaining hormone) - which governs the amount of salt lost in urine via the kidneys.

Androgen (male sex hormone) - which is intimately involved in growth and sexual development.

CAH has implications with respect to foetal development, and in particular the development of the external female genitalia. When babies begin their development within the womb, it is impossible to distinguish male and female genitalia - the "undifferentiated" genitalia of males and females look alike. In boys, between approximately 12 to 15 weeks after conception, their testes start producing androgen, which drives the "undifferentiated" genitalia to develop the male structure and characteristics.

As androgen is not normally produced in the female fetus, this "masculinization" does not occur.

In CAH, however, the adrenal glands of the female overproduce androgen and force the girl's genitalia to begin development in the male direction. Therefore, in baby girls with CAH, the genitalia may look more masculine than they should.

The clitoris is enlarged and may resemble a small penis. In addition, the cleft between the labia or lips may be partly closed over, hiding the entrance to the vagina. Often only one opening can be seen, with the urinary passage and vagina both opening into this one entrance. The internal organs, however, are quite normal - the vagina, uterus (womb) and ovaries are perfect.