Good questions Roger_ that.
My conclusion here is based upon the layout of the superficial lymphatic system, and the areas of increased hair growth induced by DHT. This also involves a consideration of how the lymphatic vessels move tissue fluid, and where most of the bodies DHT is produced. Also what really matters is proving an in-vivo effect of DHT upon lymphatic efficiency. There is an existing in-vivo study that found significant gender differences in lymphatic efficiency, and the same kind of study could confirm if DHT is responsible for this gender difference.
I think most people would agree that there is more of a direct link with the amount of DHT, and the amount of body hair growth. It is the scalp hair loss effect that is not consistent, in that you can have high levels of DHT and body hair, and either lose scalp hair or not. I think this is explained by fluid dynamics.
Increased lymphatic drainage in men would increase nutrient supply and waste removal. This would increase tissue building capacity, performance and endurance, all very useful in terms of androgenic effects. Lymph vessels move tissue fluid by contractions of the vessels, the abundant one way valves in these close when the vessels contract directing the fluid ultimately back into the main circulation.
The only logical way to increase lymphatic drainage, is to increase the natural rate of the vessel contractions. But because of the one way valves, you would have to be careful where you introduced a substance in the body designed to increase the contractions.
Most of such a substance would have to be feed into the lymph vessels at the extremities of the lymphatic system, in order to get an even increase throughout the system. If say you did this half way along the length of a lymph vessel, the increased contraction rate here would close the one way valves more often against the flow from the extremity, restricting the flow rate here. You get an opposite effect, common in many complex fluid transport systems.
I think nature has largely taken care of this issue, as most DHT production happens at the bodies extremities in hair follicles and sebaceous glands. According to Merck hair follicles produce most of the DHT at around two thirds, with sebaceous glands accounting for the rest of the dermal production. So large hair follicles can produce more DHT, and i think this accounts for the enigma of MPB.
This is how i see it. At puberty the large scalp follicles start to produce a lot of DHT. This feeds into the lower lymph vessels of the head and face, increasing lymph drainage, reducing tissue pressures to allow larger follicles, you get beard growth. These larger beard follicles produce even more DHT feeding into the lower lymph system. The MPB area is right at the end of the lymph system, and the increased lymph vessel contractions lower down creates a restriction in drainage from the MPB area. In the individual this process is linked to other vascular factors i describe in my article. This scenario is consistent with the often lengthy time periods involved in the individuals development of MPB.
For a long time now i have been trying to generate interest from scientists who can, to test the lymphatic/ DHT effect as in the study linked above. It seems that as this is not in the interest of current lines of research, i just get a no comment.
This does raise an interesting test proposal that anyone taking Finasteride could try for themselves. This could significantly boost the effect of fin to grow more scalp hair. According to this the most powerful hair growth stimulant we have is DHT. In MPB it is just a case of too much in the wrong place, we need to make DHT work for us. Finasteride does significantly reduce overall DHT production, but for maximum effect DHT needs to be re-introduced were it matters. This is as a topical on the balding scalp.
There are DHT creams out there, so any volunteers?