3-beta-hydroxysteroid dehydrogenase type II deficiency (congenital adrenal hyperplasia)

3-beta-hydroxysteroid dehydrogenase (3β-HSD) deficiency mainly affects how the sexual organs function (ovaries in females and testes in males) and is part of a family of disorders called congenital adrenal hyperplasia (CAH). CAH causes problems with hormone production and can disrupt sexual development and maturation.

3β-HSD also affects the adrenal glands, which produce hormones that regulate many functions in the body. There are three types of 3β-HSD deficiency, which vary in how serious the condition will be - the salt- wasting type (most serious), the non-salt-wasting type (less serious), and the non-classic type (the least serious form).

The most serious form of the condition can unfortunately cause life-threatening complications in early childhood, due to the increased loss of salt in the urine. With all forms of 3β-HSD, individuals can have ambiguous genitalia, which makes it difficult to tell if they are clearly male or female based on abnormal genitals. Puberty and fertility can also be problematic for both males and females with the condition.

Quick facts about 3-beta-hydroxysteroid dehydrogenase type II deficiency (congenital adrenal hyperplasia)
Genes: HSD3B2
Inheritance: Autosomal Recessive
Alternative Names: CAH, 3β-HSD
Relevant resources for 3-beta-hydroxysteroid dehydrogenase type II deficiency (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 3-beta-hydroxysteroid dehydrogenase type II deficiency (congenital adrenal hyperplasia) inherited?

3-beta-hydroxysteroid dehydrogenase type II deficiency (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 3-beta-hydroxysteroid dehydrogenase type II deficiency (congenital adrenal hyperplasia), there’s a one in four chance that their children could develop symptoms.
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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 3-beta-hydroxysteroid dehydrogenase type II deficiency (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 3-beta-hydroxysteroid dehydrogenase type II deficiency (congenital adrenal hyperplasia) before or early in pregnancy?

The biggest benefit of screening for 3-beta-hydroxysteroid dehydrogenase type II deficiency (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 3-beta-hydroxysteroid dehydrogenase type II deficiency (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.

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