Hairitage: What Your Genes Say About Going Bald

BY AMELIA LEE

The receding hairline, bald spots, and eventually a horseshoe of hair around the heads of our fathers, brothers, and many of the men in our lives. We’ve all seen the symptoms of this well-known condition. Balding is not something new to the world, but the research and treatments surrounding it are. 

What is alopecia?

Alopecia is an umbrella term relating to all kinds of hair loss. It’s present in both men and women, and although it’s seen most commonly on the scalp, it can be found over the entire body. There are many different forms of alopecia, but 95%  of alopecia seen with age is due to an inherited condition called Androgenetic Alopecia. Androgenetic Alopecia (AGA) is responsible for almost all hair loss, and affects males more vigorously than females. As its name suggests, AGA is caused by androgens, which are hormones needed for male sexual development. The most influential is dihydrotestosterone (DHT). When DHT binds to androgen receptors, it triggers hair follicle miniaturization. Hair then grows thinner and shorter each time, until it eventually stops growing completely. AGA progresses with age, due to hair follicles growing weaker as well. The hair cycle has three stages, growth, regression, and dormancy. As individuals age, their growth phase decreases, while the dormancy phase increases. 

How does genetics influence androgenetic alopecia?

It is well known that AGA is inherited, predominantly maternally, but how exactly does heredity play a role in balding? As mentioned earlier, AGA is largely due to DHT binding to androgen receptors and causing hair follicles to shrink. The AR gene is on the X chromosome and codes for androgen receptors. Males always receive their X chromosome from their mothers, and the genes that go along with it. Therefore, the severity of AGA relates to hair loss among the mother’s side of the family. When the AR gene is highly expressed, it means more DHT is able to bond at once. This causes more miniaturization and moves hair follicles out of the growthC phase much faster. Typically, higher levels of AR expression occur at the front and top of the head and lower levels at the back of the head. The greater the expression the greater the balding, which is why most men bald much more on the front and tops of their heads. In addition to AR, the EDA2R gene, which is also on the X chromosome, has an influence on AGA. The EDA2R gene inhibits new hair follicles from growing and causes cell death. Having low expression of the EDA2R can lead to more hair follicles, and thus more hair. 

What are some potential treatments? 

At the moment, there are two gene therapies in trials. The first uses CRISPR, a tool used to cut and paste genes together. It targets the SRD5A2 gene, which then lowers the amount of DHT produced and lowers the amount of follicle miniaturization. Second, stem cells can be injected into bald areas, which release growth factors and encourage follicle regeneration. While these gene therapies show promise, they’re still in the early stages of development. In the meantime, traditional solutions like hats or hairpieces remain common options for managing hair loss.

In summary, Androgenetic Alopecia (AGA) is responsible for 95% of all balding. It’s largely caused by testosterone levels, and thus affects males more. The related genes are on the X chromosome, which is why men often inherit it from their mother. While there are no current genetic treatments available, multiple are in early trial stages.