What Is DHT, and How Does It Actually Cause Hair Loss?

DHT, short for dihydrotestosterone, is a hormone your body makes from testosterone, and it drives pattern hair loss by locking onto receptors inside hair follicles that are genetically primed to respond to it. That binding does not switch a follicle off in one step. It shortens the follicle's growth phase a little more with each cycle, so the hair that grows back is finer and shorter than the one before, and after years of shortened cycles some follicles produce only a fine, barely visible hair. Only follicles carrying a particular sensitivity to that signal behave this way, which is why a receding hairline and a full, untouched patch at the back of the same head are both explained by exactly the same hormone.

• DHT is not a separate hormone your body produces on its own. An enzyme converts a portion of circulating testosterone into it.
• The damage comes from receptor binding, not from DHT floating past a follicle. A follicle only responds if it carries the right genetic sensitivity.
• Susceptibility is local and inherited, not a measure of how much DHT someone produces overall. That is why hair loss follows a pattern instead of thinning the whole scalp evenly.
• Minoxidil regrows hair through a separate route that has nothing to do with DHT or its receptor. That is worth knowing before assuming every hair-loss product works the same way.

What DHT actually is

DHT is an androgen, part of the same hormone family as testosterone, but it is not manufactured directly by the testes or ovaries in any meaningful quantity. It is made from testosterone by an enzyme called 5-alpha-reductase, which converts roughly a tenth of the testosterone circulating in the body into DHT (source: Healthline). Weight for weight, DHT binds far more tightly to the androgen receptor than testosterone does, which is the reason such a comparatively small conversion has an outsized effect wherever those receptors sit (source: StatPearls).

Where 5-alpha-reductase is active in the body

5-alpha-reductase exists in two main forms, and they are not interchangeable for this discussion. Type 2 is concentrated in the outer root sheath of the hair follicle, along with the prostate, and it is the isoform most consistently linked to androgenetic alopecia. Type 1 is found mainly in sebaceous glands, skin cells and sweat glands, which is a different tissue with a different job (source: StatPearls). Knowing which isoform sits where matters, because it explains why a treatment aimed at one enzyme type can leave the other largely untouched.

How DHT causes hair follicles to shrink

Once DHT is available near a follicle, the effect depends entirely on whether that follicle's androgen receptors are built to respond strongly to it. In follicles that are, DHT binding shortens anagen, the active growth phase of the hair cycle, so each hair spends less time growing before it sheds and the cycle restarts. That shortened phase is also progressively narrower, which is what produces the finer, shorter hair typical of early pattern loss.

Why this is a cycle, not a single event

Miniaturisation is the cumulative result of many shortened cycles, not something that happens in one pass. A healthy scalp normally carries roughly twelve anagen (growing) hairs for every one telogen (resting) hair. In scalp affected by androgenetic alopecia, biopsies show that ratio dropping as low as roughly five to one, which is the physical evidence of follicles spending less time growing and more time idle (source: StatPearls). Repeated over years, that shift is what turns a full head of terminal hair into the visibly thinner coverage associated with pattern loss, and it is also why early intervention has more follicles left to work with than a decade of untreated shrinkage does.

Why only some follicles are affected

If DHT circulated everywhere on the scalp, an unhelped reader might expect uniform thinning, but that is not what happens. Susceptibility to DHT depends on variation in the androgen receptor gene within the follicle itself, not on how much DHT a person produces overall (source: Healthline). Two follicles exposed to the same circulating hormone level can respond completely differently depending on that local genetic sensitivity.

This is why pattern hair loss follows a recognisable distribution: the vertex and frontotemporal areas in men, and more diffuse crown thinning in women, while the donor area at the back and sides of the scalp typically stays resistant for life. The same genetics explain the strong family pattern people notice, where a father's hairline history is a reasonable, though not certain, predictor of a son's risk.

Where minoxidil fits in, and why it isn't a DHT strategy

It is easy to assume every hair-loss product works on DHT somehow, given how often the hormone comes up, but minoxidil is a clear exception. Minoxidil works as a potassium-channel opener that dilates blood vessels around the follicle, which is thought to improve nutrient and oxygen delivery and to prolong the anagen phase directly. That pathway does not touch 5-alpha-reductase and does not involve the androgen receptor at all (source: StatPearls). For a fuller answer on whether minoxidil interacts with DHT at all, the separate article on minoxidil and DHT works through that question in more depth.

The practical consequence is that Minoxidil Topical Solution USP, 5% can help regrow hair in people with high androgen-receptor sensitivity and people with low sensitivity alike, because its effect does not depend on DHT levels or receptor genetics in the first place. That mechanism explains why it works at all, but it does not widen what the product is actually approved for: the approved use of the 5% solution is regrowth at the vertex, the top of the scalp, in men, and applying it to a receding hairline, the temples, a beard, or using it as a woman, falls outside that approved indication and counts as off-label use. It is not, however, a fast or a set-and-forget treatment: consistent use for four to six months, sometimes longer, is typically needed before any visible change appears, an early shedding phase is common as older hairs are pushed out by the new growth cycle, and stopping the treatment reverses the gains within a few months as the follicles return to their untreated pattern (source: MedlinePlus). Irritation and itching from the propylene glycol in the solution, and occasional unwanted hair growth on nearby skin such as the face, are the side effects reported most often, and anyone who is pregnant or breastfeeding, has a heart condition, has scalp that looks abnormal, has hair loss that started suddenly or in patches, or is under eighteen should check with a doctor before starting rather than assume the mechanism above applies the same way to their situation.

Finasteride is worth naming here only as a contrast, because it is the drug that actually does target this pathway: it inhibits type 2 5-alpha-reductase directly, which lowers scalp DHT production rather than working around it. It is prescription-only, we do not sell it, and this is not the place to weigh starting or stopping it; that decision, including dosing, belongs with a doctor who can review a person's full history.

Where a DHT-adjacent ingredient like saw palmetto fits

Saw palmetto fruit extract is the catalog example worth naming, because it sits closest to this article's subject without pretending to replace it. The product's own description notes that its fatty acids and phytosterols have inhibited 5-alpha-reductase in laboratory assays, a seller claim rather than an independently verified result, and worth treating as a lead worth watching rather than a settled finding. What that finding does not establish is an equivalent effect once the extract is sitting in a rinse-off shampoo on a living scalp: the clinical evidence on saw palmetto is limited, mostly conducted with oral supplements rather than topical products, mostly small in scale, and no published study has tested a shampoo specifically. A wash also gives the scalp only a couple of minutes of contact before the product goes down the drain, which is a very different exposure from a leave-on treatment.

That gap is exactly why the Saw Palmetto DHT Shampoo is presented as a supporting step rather than a treatment: a reasonable, honestly-labelled option for someone who wants a DHT-adjacent product in their routine, sitting alongside a therapy that has real regrowth evidence behind it, rather than in place of one. Readers who want the fuller picture on oral versus topical saw palmetto evidence, including dosing and what the actual trials tested, can follow the dedicated saw palmetto article, and anyone comparing saw palmetto against other DHT-adjacent ingredients such as rosemary oil or pumpkin seed extract will find that comparison laid out in the natural DHT blockers article.

Putting the mechanism together

Pattern hair loss traces back to a specific chain: testosterone is converted to DHT by 5-alpha-reductase, DHT binds tightly to androgen receptors, and in follicles carrying the genetic sensitivity to that binding, each growth cycle gets a little shorter until the hair produced is barely visible. None of that chain depends on how much DHT a person makes overall; it depends on which follicles are built to respond to it, which is why the pattern looks the way it does on a real scalp.

That same mechanism is what separates a DHT-focused approach from a vascular one. Minoxidil regrows hair by improving conditions at the follicle rather than by interrupting DHT production, so it works regardless of a person's androgen-receptor sensitivity, while an ingredient like saw palmetto only has evidence at the enzyme level and belongs in a routine as a supporting product, not a substitute. Building a routine around that distinction, an honestly-labelled supporting step alongside the treatment that actually has regrowth evidence, is a reasonable way to use both without overselling either. For more on the range this sits within, the Ingredients & Evidence section of the blog covers the other actives one at a time in the same way.