Start with the actual condition
Androgenetic alopecia (AGA)—often called male or female pattern hair loss—is characterized by progressive miniaturization of susceptible hair follicles. Terminal hairs become finer, shorter and more vellus-like across repeated cycles.
Androgens are part of the signal. Testosterone can be converted to dihydrotestosterone (DHT) by 5-alpha reductase. In genetically susceptible follicles, androgen signaling contributes to the miniaturization process.
Why “DHT blocker” is an incomplete phrase
The phrase makes marketing easy and biology look stupid. DHT is not a toxin floating around your scalp. Susceptibility depends on androgen receptors, local enzyme activity, genetics and follicle biology. Two people can have very different outcomes under similar androgen exposure.
Not every kind of shedding is AGA
Telogen effluvium, alopecia areata, traction, inflammatory scalp disease, nutritional deficiencies, medication effects and breakage are different problems. A routine built around “blocking DHT” is not automatically relevant to all of them.
Where Scalp Defense fits
Alrénza discusses DHT because saw palmetto is the headline botanical and its research is commonly framed around 5-alpha-reductase. We keep that discussion educational. The finished cosmetic product has not been clinically shown to treat AGA or to reduce scalp DHT by a measured amount.
Primary reference
- Whiting DA. Possible mechanisms of miniaturization during androgenetic alopecia or pattern hair loss. J Am Acad Dermatol. 2001;45(3 Suppl):S81–S86. DOI: 10.1067/mjd.2001.117428.