By matrix I mean extracellular fluids, as in blood, as in I'm tired, reading about social policy on climate change and am probably typing sloppy generic terms when I should be more precise, thus meaning you don't need to ask such questions.
My reasoning is exactly the same as I explained before. Assuming that finasteride is not specific in whereabouts in the body it inhibits DHT, then inhibition should reach near enough maximum levels in areas where there are less enzymes first. Perhaps a macro-analogy would help me illustrate my point? If not, at least I'll have a huge amount of fun typing it.
Think of finasteride molecules, or whatever its metabolites are that inhibit reductase (again, tiredness), as men. Thats right, little finasteride men. On a galivant around the neighbourhood. Lets say there are 100 men. Now, II reductase can be something that men like, like women or ice cream or something like that. On the way around the neighbourhood, the men see lots of women in some areas, too many for them to all occupy - some of the women therefore end up ignored/unmolested. They then come around a corner where there are less women, and (such is life) all of the women/ice creams get occupied/bought (take it as you will), leaving some of the men to carry on their journey alone. You can add more men, and more women on the streets which had lots of women on can get 'occupied', but all that happens on the less womany streets is a bit more competition between men. Male banter, tomfoolery, fighting, 'I'm better at having muscles than you', that kind of alpha male machismo jazz. That made perfect sense. Maybe not. But hopefully you catch my entirely questionable drift.
I'll really look into this next week, its going to be one of those go out every night/try and do something to fill the day weeks, so I have nil problem in researching more. If you have any studies which would help me with that then please share, I get that you're quite the male pattern baldness library. Anyway, hope that helps. In one sentence, a smaller amount of something means it gets saturated quicker.