46,xy difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency

This condition stems from a change in the HSD17B3 gene that reduces the body’s ability to make testosterone before birth and at puberty. It happens when a child inherits two nonworking copies, one from each carrier parent. Family history, shared ancestry, or parents who are related by blood can raise the chance of 46,XY difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency. Lifestyle or environment do not cause it, but nutrition, other health conditions, and access to timely care can affect how the condition appears and is managed. Some risks are written in our DNA, passed down through families.

Genetic risk factors

In 46,xy difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency, changes in the HSD17B3 gene limit the body’s ability to make testosterone before birth and at puberty. The condition is inherited in an autosomal recessive way, so two altered copies of the gene are needed to cause it. Only those with a 46,XY chromosome pattern develop the differences in sex development; 46,XX relatives are typically healthy carriers. Some risk factors are inherited through our genes.

• HSD17B3 gene changes: Variants in the HSD17B3 gene reduce or block the enzyme that converts androstenedione to testosterone. This is the direct genetic cause of HSD17B3 deficiency. Understanding the genetic causes of HSD17B3 deficiency can guide testing for family members.

• Autosomal recessive: A child is affected when both copies of the HSD17B3 gene carry nonworking changes. Parents are usually healthy carriers with one changed copy each.

• Biallelic variants: People may have the same variant on both copies (homozygous) or two different variants (compound heterozygous). The specific pair can influence how much enzyme activity remains and how the condition looks over time.

• 46,XY chromosomes: This 46,XY difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency appears only in individuals with 46,XY chromosomes. 46,XX family members can carry the gene change without the outward features of the condition.

• Family recurrence risk: When both parents are carriers, each pregnancy has a 25% chance the child will inherit both nonworking copies. Another 50% of pregnancies will result in a carrier child. These figures help families understand the chance of another child with 46,XY difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency.

• Consanguinity factor: Parents who are related by blood are more likely to share the same rare HSD17B3 variant. This increases the chance their child will inherit two identical changes.

• Founder variants: In some populations, a single historical founder variant in HSD17B3 became more common over generations. This clustering can raise the likelihood that two carriers meet and have an affected child.

• Variable expressivity: Different HSD17B3 variants can leave some enzyme function, so genital appearance at birth and changes at puberty can range widely. This helps explain why people with 46,XY difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency may have different clinical features even within one family.

Transmission

46,XY difference of sex development due to 17‑beta‑hydroxysteroid dehydrogenase 3 deficiency is not contagious; it cannot be caught or spread between people. It is usually passed down in an autosomal recessive way: each parent typically carries one nonworking copy of the HSD17B3 gene and is healthy, and with each pregnancy there is a 25% (1 in 4) chance the child will have the condition. There is also a 50% (1 in 2) chance the child will be a carrier like the parents, and a 25% (1 in 4) chance of inheriting two working copies. Rarely, a new gene change can cause the condition even when neither parent is a carrier. If this runs in your family, a genetics professional can explain how 46,XY difference of sex development due to 17‑beta‑hydroxysteroid dehydrogenase 3 deficiency is inherited and talk through carrier or prenatal testing options.

When to test your genes

Consider genetic testing if a newborn has atypical genital development, if puberty is delayed or progresses unexpectedly in someone assigned male at birth, or if there’s a family history of similar findings. Testing helps confirm the diagnosis, guide hormone management, and inform fertility planning. Relatives may also benefit from carrier or predictive testing.

For many living with 46,XY difference of sex development due to 17‑beta‑hydroxysteroid dehydrogenase 3 deficiency, the long‑term picture is shaped by hormone balance, timing of diagnosis, and access to expert care. In childhood, early symptoms of 17‑beta‑HSD3 deficiency can be subtle, and some people are diagnosed only around puberty when expected changes don’t appear or virilization begins. With the right support, the future can include good overall health, normal life expectancy, and the ability to thrive at school, work, and in relationships.

Looking at the long-term picture can be helpful. Many people do well with tailored hormone treatment to support their affirmed gender, routine monitoring of bone health, and counseling when needed. Fertility is usually reduced or not possible without assisted methods, but sexual function and comfort often improve with thoughtful, stepwise care. The risk of testicular cancer is higher than average when undescended or dysgenetic testes are present; decisions about gonad removal versus surveillance depend on age, location of the gonads, hormone needs, and personal goals.

The outlook is not the same for everyone, but emotional well‑being tends to improve when people have a clear care plan and feel respected in their identity. Puberty planning, including whether to use puberty blockers or hormone therapy, can lessen distress and support healthy development. As adults, many maintain good health with periodic endocrine follow‑up and attention to cardiovascular, metabolic, and bone measures common to anyone using long‑term hormone therapy. Talk with your doctor about what your personal outlook might look like.

Treatment for 46,XY difference of sex development due to 17‑beta‑hydroxysteroid dehydrogenase 3 deficiency focuses on aligning hormones and physical development with the person’s gender identity and supporting long‑term health. Care is usually provided by a multidisciplinary team, and may include hormone therapy (such as testosterone or estrogen) to support puberty, bone health, sexual function, and well‑being; some people also consider surgeries that address gonads or genital appearance, ideally timed and chosen with careful counseling. Doctors sometimes recommend a combination of lifestyle changes and drugs, and regular follow‑up monitors blood pressure, lipids, bone density, and tumor risk in any internal testes. Not every treatment works the same way for every person, so plans are individualized and can be adjusted over time. Ask your doctor about the best starting point for you, and consider psychological support to help with decision‑making and day‑to‑day coping.

Changes in a gene called HSD17B3 reduce the activity of an enzyme that helps the testes make testosterone before birth and at puberty, which drives this 46,XY difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency. A “carrier” means you hold the gene change but may not show symptoms. The condition follows an autosomal recessive pattern: when two carriers have a child, there is a 25% chance in each pregnancy that the child will inherit both gene changes and be affected. Carriers themselves usually remain healthy but can pass the gene change to their children. If you’re curious about the genetic inheritance of 46,XY difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency, testing the HSD17B3 gene can confirm the diagnosis and guide family planning discussions with a genetics professional. In some families or communities, a shared ancestor with the same gene change makes the condition more common, while others may have no clear family history.

Day-to-day, having this condition alongside other health issues can shape which hormone treatments are safe and how often labs are checked. Doctors call it a “comorbidity” when two conditions occur together. If someone also has a history of blood clots, migraine with aura, liver disease, or high blood pressure, certain estrogen or testosterone options may carry higher risks, so the care team may choose different doses or forms and monitor more closely. Low sex hormone levels can weaken bones over time; coexisting vitamin D deficiency, thyroid problems, eating disorders, or long-term steroid use can add to bone loss and raise fracture risk, making calcium/vitamin D, weight‑bearing exercise, and bone-density scans especially important. Undescended testes are linked with a higher chance of gonadal tumors, and that risk may be influenced by where the testes are located and any additional differences in gonadal development, so tumor surveillance plans can change if other urogenital issues are present. Some medicines used for other conditions—such as certain anti‑seizure drugs, antifungals, or HIV treatments—can speed up or slow down how the body handles hormones, which may require dose adjustments. Finally, early symptoms of 46,XY difference of sex development due to 17‑beta‑hydroxysteroid dehydrogenase 3 deficiency can resemble other causes of undervirilization, so when another condition is present, it can take longer to sort out what’s driving what and to tailor care.

How genes can cause diseases

Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.

Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.