The Baldness Gene

Is baldness hereditary — myth or fact?

Most male hair loss is caused by genetic disposition  

On average about 50 percent of men start losing hair when they are past the age of 40, and for some, the onset of balding is even earlier. About 80 percent of Caucasian men will bald with growing age, while for men of other ethnic backgrounds the chances of keeping their hair is around 50 percent. Other than a few rare cases of an autoimmune disorder (alopecia areata, lupus) or baldness related to external factors (radiation, chemical exposure), most male baldness can be attributed to male pattern hair loss (androgenic alopecia). 

 

In fact, androgenic alopecia accounts for around 95 percent of male baldness. With “baldness”, we here refer to the gradual multi-year process of a receding hairline that if not treated is irreversible. Of course, there’s also stress-related balding, but that’s temporary and reversible once the underlying stress disappears.

 

Male pattern baldness is genetically inherited, as has been shown by several studies. For example, one fascinating Danish study on 739 elderly twins looked for differences in the degrees of baldness between individual twins. The researchers reasoned that different levels of baldness between two twins would be explained by varying genetics. The study results showed that in 79% of cases the male pattern hair loss indeed was inherited.

 

So, where does the baldness gene come from?

For decades the conventional wisdom was that the singular culprit behind your hair loss is the androgen receptor (AR) gene, which is carried by the X chromosome. Men have both an X and a Y chromosome, with the former coming from your mother and the latter from your father. So, men would check family photos from their mom’s side to see whether they were candidates for hereditary baldness. 

 

It’s not that simple — in fact, far from it. The genetics of balding is still a relatively unchartered research territory and much remains to be explored and explained. It’s becoming increasingly clear though that you can’t simply blame the X chromosome and AR gene. AR now is thought of as a trigger specifically for early-onset pattern baldness, but not as a general genetic determinant for whether you’ll go bald one day or not. Moreover, it may not be the AR gene per se but only certain variations of it that cause such balding.

 

And then there is the Chromosome 20 (i.e., number 20 out of the 46 chromosomes that exist in your cells), which among the 500-600 genes it carries includes some genetic mutations now thought to also be responsible for androgenic alopecia.

 

Essentially, there are two things that need to come together to start pattern baldness: the genetic potential and the genetic triggers that awaken that potential. And, of course, it’s not just the genetic triggers, but external factors (the ones mentioned above, but also illness, a poor diet, and lifestyle issues like smoking and drinking) play a role as well in starting and/or worsening pattern hair loss. 

 

Recent research also suggests that chronic inflammatory processes on the scalp can trigger pattern baldness in people who have the genetic potential. To complicate things further, there is some evidence that the Y chromosome could also carry genetic triggers for balding. 

 

You now probably can sense the enormous complexity of baldness-related genetics and all the unanswered questions that there are. Many companies offer commercial DNA testing kits that claim to tell you whether you are likely to experience inherited pattern hair loss. Save yourself that money. Neither are these tests 100 percent accurate nor do they have much predictive power.    

 

Does baldness skip a generation?

It can. All genetic conditions can skip generations or siblings. But that doesn’t mean they always will. It depends on what AR genes and Chromosome 20 you inherited from your parents, whether they are mutated or not. For Chromosome 20, you also received one version from your mother and another from your father. They could both be mutated, or both normal, or only one of them mutated, etc. So, there is no firm inheritance pattern and no predictability either. Your brother could go completely bald with age 60 while you enjoy full hair all the way through your 80s.   

 

The only thing that holds some predictive power is the empirical fact that, depending on race, 50-80% of men eventually will experience hair loss. These are high odds, and every man should get himself mentally prepared for this possible eventuality. Regular monitoring of your hairline will help an early discovery of pattern baldness, and a healthy lifestyle and good scalp hygiene may delay the onset. There also are effective treatments, such as finasteride, that can stop the progress of pattern hair loss and for some men even lead to hair regrowth. Talk to a doctor to learn more about treatment options and preventive measures against male pattern baldness.  

 

References

  1. Rexbye, H., et al. “Hair Loss Among Elderly Men: Etiology and Impact on Perceived Age.” The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, vol. 60, no. 8, 1 Aug. 2005, pp. 1077–1082, academic.oup.com/biomedgerontology/article/60/8/1077/545174, https://doi.org/10.1093/gerona/60.8.1077. Accessed 8 Dec. 2019.
  2. Hillmer, Axel M., et al. “Genetic Variation in the Human Androgen Receptor Gene Is the Major Determinant of Common Early-Onset Androgenetic Alopecia.” The American Journal of Human Genetics, vol. 77, no. 1, July 2005, pp. 140–148, www.ncbi.nlm.nih.gov/pmc/articles/PMC1226186/, https://doi.org/10.1086/431425. Accessed 8 Dec. 2019.
  3. English, Robert S. “A Hypothetical Pathogenesis Model for Androgenic Alopecia: Clarifying the Dihydrotestosterone Paradox and Rate-Limiting Recovery Factors.” Medical Hypotheses, vol. 111, 2018, pp. 73–81, www.ncbi.nlm.nih.gov/pubmed/29407002, https://doi.org/10.1016/j.mehy.2017.12.027. Accessed 8 Dec. 2019.
  4. Genetics Home Reference. “Chromosome 20.” Genetics Home Reference, 2009, ghr.nlm.nih.gov/chromosome/20#. Accessed 8 Dec. 2019.

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