@IdealForehead Wouldn't the rate of hairless be linear then ? Why do some people lose all there hair in 2 years at 20 years old whilst some might thing a bit then not lose substantial amounts until their latter years etc ..?
Also what do you do for a living lol . Clearly have a scientific background yet also somehow find the time to literally write a thousand words a day on the forums.
I don't think anyone could quite answer for sure the questions of why hair loss starts at a certain point in age or why it progresses more rapidly in some men than others. However, I can offer a few theoretical explanations in the context of this research.
Primarily the initiation of balding could be conceived as the point when tension-mediated androgenic influences overwhelm the natural protective, growth, and repair functions of the follicles. The "tipping point" for this to happen would be established on an individual basis by several processes and factors. These are:
1) Subcutaneous fat under the skin of the scalp acts as a cushion for the skin, and it atrophies with age. As it atrophies, the stress the galea exerts on the hair follicles will increase. As the stress increases, androgen sensitivity and expression increase until eventually it overwhelms the natural follicular repair mechanisms. Once your reach that point, male pattern baldness begins to manifest. Additionally, increased androgens can provoke further fat atrophy creating a feedback loop.
2) Follicles in the galeal/Norwood zones may be continually upregulating androgen sensitivity genes due to mechanical stress from birth until late adulthood. Once these genes are upregulated to a significant enough degree, baldness perhaps begins, as the androgen feedback loop overwhelms the natural follicular repair mechanisms. Increased androgens will further increase galeal stress via scalp muscle hypertrophy, creating another feedback loop.
3) Galeal stress induces androgen sensitivity in the Norwood zones for different men to different degrees based on our fundamental genetics. Men for whom the galeal stress induces a great degree of androgen sensitivity will be programmed to go bald more rapidly. Men who have better adapted repair functions of their follicles would be more resistant to androgenic damage as well.
All of these processes would likely be linked. Much of male pattern baldness seems to be mediated by feedback loops.
So in this model you can see feedback between:
- Galeal tension --> Mechanical stress on hair follicles --> Androgen upregulation --> Scalp muscle hypertrophy --> More galeal tension
- Galeal tension --> Mechanical stress on hair follicles --> Androgen upregulation --> Subcutaneous fat atrophy --> More stress transmission to hair follicles
These two feedback loops may reach a "tipping point" at a certain stage of life for each man, and each area of the scalp. The difference between one man and another in terms of how strongly these feedback loops operate and how resilient the natural hairs are to avoid miniaturizing in this context would be genetic factors beyond our control.
In the context of feedback loops, hair loss would therefore be expected to follow a sigmoidal curve, where the rate of balding is virtually zero at the beginning of life, then reaches a point where it rises exponentially (as the feedback loops reach the "tipping point" where they overwhelm repair mechanisms), and then lastly a stable rate of balding, where the feedback loops are operating at maximum capacity until baldness is complete.
Such a curve would look something like this:
For reference, that graph was adapted from
here, and incidentally, it models a bacterial growth rate. These types of curves are common in nature.
I don't like to say too much personal about myself, but the main reason I've been able to post so much the past few weeks is I was off work for my hair surgery, and hair has been the only thing on my mind. I have an obsessive personality, so when I start focusing on something (like hair) it becomes consuming. That can be good because I can get a lot done and dive deeply into an area of interest. But it means I need to prioritize where I put my attention as well. I stopped posting here for a few months for that reason. As much as I like it here, and enjoy the community, it will therefore likely become necessary for me to do the same again soon.
I have also reached a point where I feel I am no longer so curious or concerned about the balding process. I feel I have sufficient answers that my curiosity has been sated. I have additionally found numerous treatments that seem to be working for me, and I have more already lined up to try next (eg. equol, genistein), so my hair anxiety is settling. At a certain point, I will again need to focus on other areas of life.
I hope all this has been interesting. I have found it interesting myself, and I think in the long run, the science will confirm much of this to be correct.