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17-alpha-hydroxylase-deficient congenital adrenal hyperplasia

Congenital Adrenal Hyperplasia (17-Alpha-Hydroxylase-Deficient, 17-OHD) is one of a group of disorders (collectively called congenital adrenal hyperplasia, CAH) that affect the adrenal glands. The adrenal glands are located on top of the kidneys and produce a variety of hormones that regulate many essential functions in the body. In people with Congenital Adrenal Hyperplasia (17-OHD), the adrenal glands produce excess androgens, which are male sex hormones.

There are two types of Congenital Adrenal Hyperplasia (17-OHD): the complete form and the partial form. The complete form is the more severe of the two types, often causing symptoms such as abnormal genitals (ambiguous genitalia), low potassium levels in the blood and high blood pressure. Females with Congenital Adrenal Hyperplasia 17-OHD may not develop breast or pubic hair and may have irregular or absent periods. With appropriate treatment and management, people affected by Congenital Adrenal Hyperplasia (17-OHD) have normal life expectancy.

Quick facts about 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia
Genes: CYP17A1
Inheritance: Autosomal Recessive
Relevant resources for 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia

A quick genetics rundown

As humans we have about 23,000 genes. These genes are like tiny instruction manuals that influence our health, growth and development. We inherit half of our genes from our biological mum and the other half from our biological dad. These genes are lined up on structures called chromosomes. Most of us have 23 pairs of chromosomes. The first 22 pairs are called autosomes and for the most part - these are the same among men and women. The 23rd pair determine our sex - two X chromosomes for a female and one X and one Y chromosome for males.

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How is 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia inherited?

17-alpha-hydroxylase-deficient congenital adrenal hyperplasia is known as an autosomal recessive condition. For autosomal recessive conditions, if a person has a variation in one copy of their gene, they are a carrier. This means that they are healthy because they also have a working copy of the gene. But, they can still pass their non-working copy to their child.

If the other parent also happens to be a carrier of the same gene, there is a 25% (1 in 4) chance that they both pass this gene variation on to their child — and as such, have a child affected by the disease.

If both parents are carriers of 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia, there's a one in four chance that their children could develop symptoms.

What is carrier screening?

Carrier testing is like a checkup for your genes. It tests to see if you carry a gene variation that could cause a serious genetic disease in your child. Eugene offers an inclusive genetic carrier screening panel that includes 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia, but there's a total 301 conditions that can be tested.

Eugene's carrier test is a clinical grade test that can be done from the comfort of your own home — it's just a saliva test. You're also paired with a genetic counsellor who provides mindful support and guidance every step of the way.

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Should parents screen for 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia before or early in pregnancy?

The biggest benefit of screening for 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia is that it can help future parents understand their reproductive risk so they can be ready and empowered to make more informed decisions. If neither partner are carriers, it provides reassurance and peace of mind that the risk of having a child with a genetic disease is low.

Since 90% of children that have a recessive genetic disease like 17-alpha-hydroxylase-deficient congenital adrenal hyperplasia had no previous family history of it, it often feels completely out of the blue for the parents. Getting screened is a way to know this risk in advance, which can help familes manage or even prevent the disease in the first place.