That is what I am asking.
I don’t know if have any sense.
I would like to reduce DHT in the scalp and not in the blood
The claim made on hair loss forums is as follows:
DHT is an autocrine hormone and is used mostly within the cells where it is produced. Therefore, only "scalp DHT" (or DHT produced in the dermal papilla) contributes to hair loss.
^If the above was true, then the following must also be true:
1) Serum DHT, or DHT in any other location in the body does not contribute in any way to hair loss
2) Applying DHT topically anywhere, should not cause any kind of systemic effect, certainly not hair loss, and should only affect the cells where it has been applied
However, this study shows that topically applied DHT in sufficient doses can even completely shut down the production of sex hormones:
"The extremely high serum levels of DHT achieved in this study lead to significant gonadotropin suppression, thereby reducing circulating testosterone levels to nearly castrate levels and reducing circulating estradiol levels by 90%."
(
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3192006/)
This means that serum DHT has no problems binding to androgen receptors in the brain and downregulating FSH and LH. If it binds to androgen receptors in the brain then I don't see why it would have any problems binding to androgen receptors in the hair follicle.
The amount of DHT in the hair follicle is, in all likelihood, a sum of locally synthesized DHT and DHT resulting from spillover from systemic circulation.
Depending on what % of DHT comes from the DP itself, even the best topical Finasteride/Dutasteride will probably only have a limited effect.