Congenital adrenal hyperplasia (CAH)

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders that result in impaired hormone production from the adrenal glands. The most common form of CAH is caused by a deficiency of the enzyme 21-hydroxylase (21-OHD) which accounts for over 90% of people with CAH (White & Speiser 2000 PMID: 10857554).

This condition is extremely variable and depends on the level of impairment of production of cortisol and aldosterone. Classical CAH, due to severe enzyme deficiency, can be divided into two phenotypes: salt wasting (SW) and simple virilising (SV). SW is the most severe form of CAH and can be a life-threatening condition if not recognised and treated. In SV CAH, virilisation occurs because of increased production of male sex hormones by the adrenal glands. The non-classical form of CAH is due to mild enzyme deficiency and patients may present with mild symptoms of androgen excess.

CAH is caused by disease-causing variants in the CYP21A2 gene. There is some correlation between CYP21A2 genotype and phenotype. Our assay will detect at least 90% of all CYP21A2 variants.

NHSE test directory code: R180 Congenital adrenal hyperplasia.

Visit the NHS Genomic Test Directory 

Eligibility criteria for genomic tests can be found in the National Genomic Test Directory.

This lists the clinical specialties that would be expected to request for a given clinical indication and sets out which patients should be considered for testing.

All samples for genomic testing should be accompanied by a fully completed request form.

The request form should include as much clinical information about the patient or family member, family relationships and the requested test code (R number). All request forms must indicate either a specific disorder/gene(s) to be investigated or, a request to extract and store DNA.

This form should be used for the majority of test requests.

Please do not download and store this on your desktop or system. The form is regularly updated. Our recommendation is to save or bookmark a link to our website to ensure you are working with the most up-do-date version.

Download the latest version here: GMS Test Order Form v2.3

An appropriate discussion of genomic testing and the possible implications for a patient and their family members must take place before testing is requested.

It is the referring clinician’s responsibility to ensure that the patient/carer knows the purpose of the test and that the sample may be stored for future diagnostic testing. In submitting a sample with a request form, the clinician confirms that informed consent has been obtained for (a) testing and storage (indefinitely) (b) the use of this sample and the information generated from it to be shared with members of the donor’s family and their health professionals (if appropriate). The patient should be advised that the samples may be used anonymously for quality assurance and training purposes.

If stated as a requirement for a specific test, a record of this discussion must be retained within the patient record when a genomic test is ordered.

For more information please view the Consent and Confidentiality in Genomic Medicine guidelines from the Joint Committee on Medical Genetics.

Before sending samples for genomic testing, please ensure you follow the correct preparation and transport guidelines. This includes information on sample types, volumes, handling, labelling, and packaging standards.

For a full list of sample requirements and transport guidance, please visit the samples and transport page of the website. 

For diagnostic referrals please also send samples from parents, where possible, to aid the interpretation of any variants identified.

Turnaround times (TATs) for genomic tests are continually refined through ongoing reviews of testing standards.

Results will be returned to the email account or clinician listed on the request form.

Visit the results and turnaround page for more information.

Visit the results and turnaround page for more information.