Jimenez, J. J., Wikramanayake, T. C., Bergfeld, W., Hordinsky, M., Hickman, J. G., Hamblin, M. R., & Schachner, L. A. (2014). Efficacy and Safety of a Low-level Laser Device in the Treatment of Male and Female Pattern Hair Loss: A Multicenter, Randomized, Sham Device-controlled, Double-blind Study. American Journal of Clinical Dermatology, 15(2), 115–127.
From what I’ve seen and read they can be quite effective–but come with several risks (scarring and unnatural-looking hairline come to mind). I haven’t dwelled much into it, but basically got FUT (follicular unit transfer), FUE (follicular unit extraction) and DHI (direct hair implant)–which is the newest, similar to FUE, most costly and provides the best results in most cases.

What’s got less evidence supporting its efficacy are the hair-growth shampoos that claim to block DHT (like those sold by Hims in their Rx Hair Kit). Rieder is skeptical that you’re going to see any tangible benefits by rubbing DHT blockers into your scalp. “I find it very difficult to believe that something that’s applied to the scalp and rinsed off is going to have any appreciable effect.” All four doctors also shut down any suggestions that hair-growth supplements or vitamins, like biotin, could help promote hair growth or stop hair loss — though a couple hypothesized that vitamins or supplements could lead to hair regrowth if your hair loss was a result of a nutritional deficiency. But otherwise, if you’re dealing with regular old male-pattern baldness, “There is no such thing as a ‘hair vitamin,’” says McMichael.

Topical treatments like Rogaine use the active ingredient minoxidil -- originally used to treat high blood pressure. After researchers discovered that it also promoted hair growth, it was the first drug approved by the FDA to treat male pattern baldness. It is used topically on the scalp, and the success of treatment is dependent on the user's extent of hair loss. Researchers at the AHLA find its efficacy to be marginal in the long run since it has no effect on the hormonal process. 
Hi, great article. I have an aggressive form of MPB. I am 23 year old with a NW2 hairline, diffuse thinning over the top and crown. Been on 5% Minoxidil and 2% Keto for about 9 months. Went through a period of shedding which has reduced somewhat in the last couple of months. I don’t see any appreciable increase in density anywhere but I do see plenty of thin vellus hair at my hairline. I am waiting for the 1 year mark to see the full effect of this regime. Is there like a test you can do to assess hairfall? Or do we just have to count the hair lost in the shower? Do you reckon I should start the Fin to hold on the the hair I have? Like most guys (actually a bit more than most guys seeing that I am young) I worry a lot about being in the 2% who experience disastrous sides from Fin. I do plan to check my DHT levels before I start, if I do at all, to see if I naturally have high/low DHT. That should tell me what to expect, to an extent.
In either sex, hair loss from androgenetic alopecia occurs because of a genetically determined shortening of anagen, a hair's growing phase, and a lengthening of the time between the shedding of a hair and the start of a new anagen phase. (See "Life cycle of a hair.") That means it takes longer for hair to start growing back after it is shed in the course of the normal growth cycle. The hair follicle itself also changes, shrinking and producing a shorter, thinner hair shaft — a process called "follicular miniaturization." As a result, thicker, pigmented, longer-lived "terminal" hairs are replaced by shorter, thinner, non-pigmented hairs called "vellus."
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