Different types of CAH
There are many different grades of severity of CAH depending on the degree of impairment of production of cortisol and aldosterone. In the most severe type of CAH aldosterone is completely lacking and loss of salt from the body is the most prominent problem - salt losing CAH accounts for 80% of children with CAH. The loss of salt in the urine is uncontrolled and can cause acute dehydration, very low blood pressure and vomiting. The levels of salt (sodium and chloride) and sugar (glucose) fall in the blood, and the potassium level rises. This is an 'Adrenal Crisis' needing very urgent treatment as a potentially life threatening condition.
In the 20% of children with less severe CAH, non-salt losing CAH, the salt balance is normal. In stressful situations, however, some people with non-salt losing CAH may become salt losers and need extra treatment. Girls born with non-salt losing CAH are usually healthy, but often born with an enlarged clitoris and the labia may be partially fused because of the excess of testosterone. Generally, this is less severe than that seen in salt losing cases. In boys, non-salt losing CAH produces no detectable signs at birth and the diagnosis is made when the penis enlarges at a very early age along with early pubic hair and rapid growth in height the result of high levels of testosterone. These changes may not occur until 4 or 5 years old.
The mildest form of CAH - late onset CAH - affects women at any age. Symptoms of unwanted hair growth or irregular periods can start at any time after puberty. Often treatment with steroids is not necessary in women with late onset CAH. Instead, giving oestrogen as in the oral contraceptive can regulate testosterone from the ovary. In fact, the treatment of late onset CAH is usually the same as for the polycystic ovary syndrome because the two conditions are so similar. In men, late onset CAH usually goes unrecognised although it may cause the sperm count to be low.
All of the types of CAH above are deficiencies of the enzyme 21 hydroxylase which account for over 90% of people with CAH. The next most common deficiency is of the enzyme 11-beta hydroxylase. Treatment of this type of CAH is more complicated because high blood pressure can be severe if treatment inadequate. The balance of treatment in 11-beta hydroxylase deficiency is very difficult and an experienced specialist is essential. Deficiencies of other enzymes are exceedingly rare.
Many thanks to Dr Gerard Conway, UCLH (University College London Hospital), 250 Euston Road, London NW1 2PQ for help with this section