The 3 main steroids involved in CAH are:

• Cortisol controls how the body copes with stress, emotional and physical, such as infection or injury. It also helps to control blood sugar levels, raising these levels if they become too low particularly in children.
• Aldosterone helps to regulate the salt levels in the body. Aldosterone causes the kidneys to conserve salt if there is too little salt in the diet, or if a lot of salt is lost due to excessive sweating. Conversely, if a lot of salt is eaten the adrenal cortex reduces the amount of Aldosterone secreted, allowing the excess salt to be passed in the urine.
• Androgens are a group of male hormones, one of which is testosterone. Testosterone is produced by the adrenal cortex in both males and females and they control the formation of pubic hair at the onset of puberty. Testosterone is also produced by the testis and in small amounts by the ovary.

There are five main enzymes in the adrenal gland which convert cholesterol into the important steroid Cortisol. If any of these enzymes are missing or defective then not enough Cortisol is made for the needs of the body. The body, recognising the low levels of Cortisol, will try to stimulate the adrenal cortex to make more by ‘pushing’ the gland harder by a stimulating hormone called ACTH made in the pituitary gland. The constant unsuccessful stimulation causes the cortex to increase in thickness and become ‘hyperplastic’.

In the most common form of CAH there is a deficiency of an enzyme called 21 hydroxylase. In this form of CAH the production of Cortisol and Aldosterone is low while testosterone, the male hormone, is produced normally. As the body pushes the adrenal gland harder trying to correct the low Cortisol level more and more testosterone is made. In boys, this excess of testosterone causes early sexual development. In females, the excess in testosterone can cause abnormal genital development before birth while in adults it causes irregular periods, unwanted hair growth and acne. Only by correcting the levels of Cortisol with substitute therapy does the body recognise normal levels and stop producing excessive amounts of testosterone and the circulating levels become normal.

The hormone disturbances caused by CAH:

• Lack of Cortisol
• Lack of Aldosterone
• Excessive androgens

MORE INFORMATION What is CAH? Steroids and CAH Different types of CAH CAH Genetics FAQs

Many thanks to Dr Gerard Conway, UCLH (University College London Hospital), 250 Euston Road, London NW1 2PQ for help with this section