A certain type of male hormone (androgens) can have a significant impact on hair growth, leading to androgenetic alopecia or male pattern baldness (MPB).
Androgens affect numerous biological functions in different ways, by interacting with certain receptors located within cells or on cell membranes (as with all hormones).
Hair follicles located in different areas of the body may respond to the same androgen differently, e.g. armpit hairs might grow while hairs on the scalp fall out.
There are 3 key factors involved in this type of hair loss, tied closely together.
First of all, androgenetic alopecia only occurs in men with a specific genetic code in their chromosomes.
This is typically carried by one or more genes, and can be inherited from one or both parents.
While it was formerly believed that this condition came from the mother and affected her sons only, that’s no longer the case.
Androgenetic hair loss is inherited in an autosomal dominant manner, which means that the gene responsible may be passed on by the mother or father.
And this problematic genetic code may cause hair loss in men AND women, so sons and daughters could be affected equally.
But simply carrying the gene is no guarantee of baldness.
The gene must be “expressed” to be activated, which hinges on numerous factors including age, stress levels, hormones, and more.
If an individual shows no signs of developing pattern baldness, the gene responsible is either missing or not expressed.
The specific gene or group of genes causing androgenetic hair loss are still unidentified, though experts believe they’re involved in synthesising male hormones — enzyme 5-alpha reductase (which converts testosterone into dihydrotestosterone or DHT) and androgen receptors found within hair follicles.
Enzyme 5-alpha reductase is more active in balding areas, as it increases the amount of testosterone converted into dihydrotestosterone and the speed at which hair loss occurs.
As a result, dihydrotestosterone can cause hair growth cycles to become increasingly shorter, reducing the anagen phase significantly.
The other stages (catagen, telogen, exogen) will all continue as normal, leaving the scalp with fewer new hairs to replace those being shed.
Hairs will become shorter and thinner, leading to weakened hair shafts.
As specialists continue to unlock more mysteries of genetic medicine, they’re sure to identify the gene(s) causing male pattern baldness in the future.
That will lead to more proactive treatments for androgenetic alopecia, even allowing experts to predict if babies are likely to be affected as adults.