The Thinning Gender Divide: The Genetic Basis of Male and Female Pattern Baldness

BY GRACE DJABRE

Let's do a short exercise.

Close your eyes, breathing in and out for ten seconds. Then, with your eyes still closed, imagine a bald person. 

What did you envision? A male with a horseshoe-like or ‘M’-shape recession starting at the top of the head? With a comb over, perhaps? 

Although hair loss is largely considered a male condition, roughly 33% of women experience hair loss at some point in their lives. 

Androgenetic alopecia, also known as male-pattern baldness (MPB) or female-pattern baldness (FPB), is the most common type of baldness. Although aging is a commonly noted factor, genetics plays a key role in severe hair loss. 

What is the difference between MPB and FPB?

The symptoms of baldness vary between males and females. MPB usually starts with a receding hairline at the temples and crown area, forming an "M" shape. As the hair follicles become thinner, a horseshoe pattern develops and hair remains around the sides and back of the head. Males typically experience balding around their twenties and thirties, and 80 percent of men experience MBP by 80 years of age. 

FPB, however, starts with hair thinning on the crown of the scalp, followed by hair loss throughout the scalp. Females typically experience baldness after menopause and don't have receding hairlines. Roughly a third of women experience FPB by 80 years of age.

FPB is caused by a combination of genetic and hormonal changes, but genetics plays a less important role in female hair loss. Hormonal imbalances, due to pregnancy and menopause, and a decrease in estrogen contribute to baldness in females.

What causes MPB and FPB?

FPB is caused by a combination of genetic and hormonal changes, but genetics plays a less important role in female hair loss. Hormonal imbalances, due to pregnancy and menopause, and a decrease in estrogen contribute to baldness in females.

The main cause of androgenetic alopecia, more specifically with MBP, is genetics. Interestingly, studies involving twins estimate that genetics accounts for 80 percent of MBP.

Individuals with a predisposition to baldness have mutated AR genes located on the X chromosome. This gene provides instructions for producing androgen receptors, which act as hair growth regulators. With AR gene mutations, the hair follicles become overly sensitive to dihydrotestosterone (DHT), an androgen converted from testosterone that activates the androgen receptors. DHT then causes hair follicles to shrink, leading to hair thinning and baldness.

Baldness is a polygenic trait, so multiple genes contribute to its development. While the exact inheritance pattern of the balding phenotype isn't fully understood, the AR gene follows X-linked inheritance. Specifically, the mutated gene is passed down from the mother to her offspring. 

Males would need one copy of the mutation for MPB because they have one X chromosome, inherited from the mother, and one Y chromosome, inherited from the father. Females, on the other hand, would need two copies of the mutated X chromosome for FPB to occur, as they have two X chromosome copies.

Androgenetic alopecia is caused by genetic and hormonal factors. Although this condition cannot be prevented, steps can be taken to promote hair growth and slow down its development. Maintaining healthy stress levels, eating healthy, avoiding harmful hair products, and taking medications like finasteride and minoxidil can preserve hair.

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Yetman, D. (2020, November 24). How to fight the baldness gene (and other factors). Healthline. https://www.healthline.com/health/baldness-gene#other-causes

Admin-Science. (2023, December 20). Understanding the role of genetics in baldness: causes, factors, and prevention. Genetics. https://scienceofbiogenetics.com/articles/the-role-of-genetics-in-male-pattern-baldness-understanding-the-genetics-behind-hair-loss