What Causes Baldness?
You’re standing in front of the mirror trying to figure out why your hairline is retreating. Is it job stress? Your child pulling on your locks to wake you up every morning? Possibly, but evidence suggests it’s more to do with your genes.
Hair loss affects both sexes: 50% of males and 25% of females experience balding, and whilst hair loss is more common in men, women experience more hair thinning than outright loss.
Sleeping hair follicles
Hair follicle growth occurs in cycles of growing, resting and falling out. In humans this cycle is quite long compared to other mammals – between two and six years. Baldness begins with a shorter growing phase of the hair follicles and a reduction in the size of the follicles, making the hairs less healthy and prone to falling out. Eventually, the follicles become dormant and stop producing hair altogether.
One commonly cited player causing this is dihydrotestosterone (DHT), a sex hormone derived from testosterone. During puberty, DHT helps men to develop body hair and a deep voice, and later in life maintains muscle mass and fertility. Higher levels of DHT in the skin affects the hair growth cycle, shortening the growth phase and causing the follicles to gradually stop growing hair.
Men with male pattern baldness often have higher levels of DHT. Often, higher levels of DHT can be due to genetic variances in receptor of DHT and in the enzymes that produce DHT from testosterone. But high DHT levels are not a definitive cause: men and women with baldness can also have normal or even lower levels of DHT and testosterone. Simply put, the cellular mechanisms that cause hair follicles to stop growing hair are not fully understood.
In women, hair loss is common with age and is common around menopause. Clearly, like in men, hormonal changes play a key role in balding, but it will take many years to find out the full story.
You get it from your mother’s side – or your father’s
There is a commonly repeated myth that baldness comes from your mother’s side. Possibly, but you’re just as likely to inherit it from your father, or both.
The genetics behind baldness are complex: over 200 genetic variances correlate with male pattern baldness, and we don’t know how these variances cause baldness.
But, correlation doesn’t mean causation – knowing what genetic variances you have doesn’t necessarily predict whether you’ll become bald or not. Indeed, it isn’t certain you’ll become bald if the menfolk in your family sit around the dinner table looking like eggs in an eggbox.
So what about factors such as stress and hair pulling? Indeed, chemotherapy, pregnancy, air pollution, stress and even Covid-19 can all play their part, and what about environmental factors? It is estimated that 80% of the variance of baldness is estimated to be genetic, with the remaining 20% being associated with environmental factors. It is tricky to nail down whether your lifestyle causes balding, but things like stress, air pollution, and even Covid-19 can possibly accelerate baldness if you are already genetic predisposed.
It seems, like most things in our lives, that baldness is an interplay between our genes and the environment, so thanking your kids or your boss for your baldness may only be partly deserved.
By Fred Schwaller PHd
Neuroscience Research Scientist (…and Martin’s son)