The hormones testosterone and its derivative dihydrotestosterone are, along with genetic factors, responsible for causing this type of hair loss in over 80% of men and about 50% of women.
That’s a lot of people!
In fact, this is by far the most common type of hair loss affecting millions of men and women around the world.
So why does it affect so many people?
Cause of Androgenetic Alopecia
There are three important hormone-related areas to consider:
1. How these hormones act.
2. How they fit in with the current theory.
3. How these hormones are produced.
1. How these hormones act: Bone, muscle and hair growth… and hair loss!
Testosterone and dihydrotestosterone (DHT) are steroid hormones (androgens) and, as such, have an anabolic effect. In other words, they make things grow.
That’s why, during puberty when levels of these two hormones increase, men experience a big surge in bone and muscle growth.
But these hormones also promote the growth of hair – testosterone develops pubic hair growth, and dihydrotestosterone develops facial and body hair growth. So that raises the question:
How can these hormones be linked to both hair growth and hair loss?
The current theory for this type of hair loss cannot explain this apparent paradox…
2. The current theory
The current theory was developed after it had been observed that castrated men (eunuchs) tend to keep their hair and not suffer male pattern baldness. Clearly then, without normal levels of testosterone and dihydrotestosterone, hair loss will not develop.
Subsequent research also reported the following:
- Hair follicles in the hair loss region of the scalp appear to contain more androgen receptors and 5-alpha reductase than in the rest of the scalp.
- The enzyme 5-alpha reductase converts testosterone into dihydrotestosterone (which is about five times more powerful than testosterone).
- Dihydrotestosterone then binds to the androgen receptors much more so than does testosterone, and accumulates within the hair follicles.
- Increased levels of dihydrotestosterone can be found in the hair loss region of the scalp in people who suffer androgenetic alopecia.
All of which led to the current theory, which states that high levels of dihydrotestosterone must be responsible for the miniaturization of hair follicles and the hair loss which then develops, but exactly how dihydrotestosterone does this is not known!
So that explains how dihydrotestosterone fits in with this type of hair loss.
But how is this hormone produced?
3. Hormone production: Food, hormones and hair loss are all connected
The very simplified pathway below shows how testosterone and dihydrotestosterone are formed in both men and women.
Fat → Cholesterol → Testosterone → DHT
From this pathway you can see that these hormones are derived from cholesterol. And cholesterol is, of course, derived from the foods we eat.
It follows then, that the more foods you eat which get processed into cholesterol, the more testosterone, dihydrotestosterone and, ultimately, hair loss you might develop.
This is the main connection that food has with androgenetic alopecia. Learn more about the link between hair loss and food – Read this page.
Although it’s dihydrotestosterone which is most often given the blame for androgenetic alopecia, the link between dihydrotestosterone and hair loss is only part of the story.
Genetics also plays a very big role…
Several genes have been identified which are connected to androgenetic alopecia in some way. These include the 5-alpha reductase and androgen receptor genes (the relevance of which was explained in the last section).
However, it’s widely accepted that the genes which actually initiate this condition remain unknown. And, as such, the current theory simply states that hair follicles must be “genetically programmed” for hair loss.
But, I believe the reason why these genes have not been identified is because scientists are looking in the wrong place!
No one, it seems, is currently studying the bones of the skull that underlie the scalp.
If they did, they should be able to confirm my own theory for this type of genetic hair loss:
Most men suffer quite severe hair loss from androgenetic alopecia, which develops into areas of total baldness, as shown below:
Receding temples in the frontal region…
A bald spot or patch at the back…
Severe hair loss at both the front and back usually develops into the familiar male pattern baldness profile…
As you can see, men might lose hair from the front, back, or both. Or they could just develop thinning hair rather than areas of baldness.
So why do all these different regions and varying degrees of hair loss emerge?
The current theory gives no real explanation – it simply states that the hair follicles must somehow be “individually programmed” in one region of the scalp but not in any other.
Women produce much lower levels of testosterone and dihydrotestosterone than men. And this, along with genetic factors, explains why most women do not develop severe hair loss, whereas most men do.
So instead of developing areas of total baldness, women generally tend to experience thinning hair (diffuse hair loss) and do so in exactly the same region as in men (see photo on the left below).
From the photo on the right, you can see that this lady appears to have developed frontal baldness, and not diffuse hair loss across her scalp. So, for some women, more severe and localized hair loss can develop instead.
All these different patterns of hair loss in men and women have also been formally classified, as explained below.
How to measure hair loss
For men, the Hamilton-Norwood scale is often used to gauge androgenetic alopecia development.
From the diagram below, you can see that there are seven stages of hair loss, but also two variations:
Anterior – Addresses recession of the entire front hairline (i.e., not just the temples).
Vertex – Addresses early-stage baldness developing on the top of the head.
A further modified Hamilton-Norwood scale also exists whereby a stage II vertex version has been added (not shown in the diagram).
For women, the Ludwig scale can be used to show androgenetic alopecia development and is largely based upon the width of a middle parting to indicate the extent of hair loss, as you can see from the diagram below.
However, there’s also the Savin scale. This is virtually the same as the Ludwig scale but has more detail of hair thinning and hair density. For both scales, female hair loss classification involves three stages divided into seven variations. But the Savin scale also has two further variations:
Advanced hair loss (i.e., baldness of the crown)
Frontal hair loss (i.e., receding temples)
Note: Both these versions are very rare in women and are not shown in the diagram.
A few notes:
1. Notice from the Ludwig scale that the area of hair loss in women is exactly the same as it is in men whereby the sides of the head remain unaffected. This differs from telogen effluvium which causes hair thinning across the whole scalp.
2. The Hamilton-Norwood scale has more stages than the Ludwig scale – this reflects the greater variety and severity of hair loss in men than in women.
3. The first image in each diagram represents no apparent hair loss.
Many hair loss patients and practitioners find these scales useful. But, as you can see, hair loss classification can be quite complicated!
So, personally, I prefer my own much simpler version, which can apply to both men and women:
Mild – You notice an increase in hair loss (e.g., comb, basin, pillow) but no one else does. Most likely to apply if your hair loss has only recently started.
Moderate – Thinning hair and reduced hair density makes your hair loss noticeable to both you and others. Can apply to rapid or medium-term hair loss.
Severe – Your scalp clearly shows through your remaining hair, and you might even be completely bald in some areas. Most likely to apply to long-term hair loss.