Concerning thinning hair, would it be accurate to say that something like decrease in hair density (without miniaturization) might be temporary and stress-induced, but evidence of miniaturization would almost certainly be MPB? Is miniaturization obvious from hair diameter or does it require magnification?

Hair grows in groups called Follicular units which contain between 1-5 hairs each along with one or two vellus hairs. With age or genetic balding, the hair count within these groups can be reduced making a person’s hair look thinner (less full).

This mas is 24 days after his crown hair transplant.  The healing crown itched and he responded by scratching it. Scratching it breaks the fragile skin of the recipient area and makes it vulnerable to the invasion of bacteria that normally reside on the scalp and in the pores of the scalp,  These bacteria are opportunists and take hold as shown in this photo. It is easily addressed with antibiotics

This is an excellent response from topical finasteride and topical minoxidil use for one year started at 23 years of age

Female taking dutasteride for thinning hair over a 6 month period of time. Young women who getting pregnant while on dutasteride will condemn their baby with physical sexual identification problems.

From the New York Times, this article discusses verteporfin, a new miracle drug for preventing scars: https://www.nytimes.com/2021/04/22/health/surgery-scar.html

According to the article, this drug is not yet FDA approved for use in humans for the prevention of scarring.

Too many young men want to prescribe their own dose to avoid the 2-4% risks of sexual side effects.  That may not make sense.  When Merck did the original study for the best dose of finasteride across a huge group of men, they found that the 1mg daily dose was the most effective dose. Higher doses didn’t effect the balding more than the 1mg dose, Lower doses, were less effective with a half dose at about 80% as effective as the 1 mg dose. In their data, the .25 mg dose was only 50% as effective as the 1 mg dose. So when I prescribe it, I prescribe the 1mg daily dose.

How much shed should I worry about?

Average scalp sheds about 100 hairs/day with a cycle of 3 years. That is 100,000 hair shed over almost 3 years, just do the math). If the cycle is shorter like a two year cycle (anagen to telogen cycle) then more hair loss can be expected and it would be normal. With the average Caucasian having 100,000 hairs and a two year cycle (which may be the case in some men in their early 20s), that would be 50,000 hairs/year shed (137/hairs per day shed would be normal).