DHT and the hair growth cycle explained

The hair follicle grows in repeating cycles

Each hair on the scalp is produced by a follicle, and every follicle moves through a repeating sequence of phases rather than growing continuously. Scientists generally describe three main phases:

• Anagen — the active growth phase during which the follicle builds a hair shaft
• Catagen — a short transition phase in which growth stops and the lower part of the follicle regresses
• Telogen — the resting phase, at the end of which the existing hair is released and a new anagen phase begins

Some descriptions add a shedding step, sometimes called exogen, to account for the release of the old hair.

Follicles cycle independently of one another, so at any given moment a scalp contains hairs in different phases at once. This mosaic pattern is why healthy scalps shed some hairs every day without any visible change in overall coverage — the follicles releasing resting hairs are balanced by others in active growth. The length a hair can reach is tied to how long its follicle stays in anagen, since that is the window in which the shaft is actively lengthened.

Understanding this cycle is the foundation for understanding pattern hair thinning. The phases themselves are a normal part of follicle biology; what changes in androgenetic (pattern) hair loss is the balance and duration of those phases in genetically susceptible follicles. That is where the androgen dihydrotestosterone enters the picture.

What DHT is and how the body forms it

Dihydrotestosterone, usually shortened to DHT, is an androgen — a class of hormones that includes testosterone. The body does not secrete DHT directly in large amounts; instead, it forms DHT from testosterone through the action of an enzyme called 5-alpha-reductase. This enzyme exists in more than one form, and the different types are concentrated in different tissues, including skin, hair follicles, and other androgen-responsive areas of the body.

Because DHT is generated locally by this enzymatic conversion, its concentration can differ from tissue to tissue rather than being uniform throughout the body. In tissues where 5-alpha-reductase is active, testosterone arriving through the bloodstream can be converted into DHT right where receptors are present. This local conversion is one reason DHT is often discussed specifically in the context of skin and follicle biology.

DHT is described in pharmacology as a potent androgen because of how tightly it interacts with the receptor that androgens act on, which is discussed in the next section. It is a normal part of human physiology and plays roles in development and in various tissues; its relationship to scalp follicles in genetically susceptible people is only one aspect of a broader biological role.

How DHT acts at the androgen receptor

Androgens exert their effects by binding to the androgen receptor, a protein found inside cells that belongs to the family of nuclear hormone receptors. When an androgen such as DHT binds to this receptor, the receptor changes shape and the resulting complex moves into the cell nucleus, where it can influence which genes are switched on or off. In this way, the receptor acts as a bridge between a circulating hormone and the activity of the cell.

DHT is understood to bind the androgen receptor with greater affinity than testosterone does, and the DHT–receptor complex tends to remain associated for a longer period. In practical terms, that means DHT can produce a stronger and more sustained androgen signal in a tissue than an equivalent amount of testosterone. In hair follicles, the androgen receptor is present in cells of the dermal papilla, the specialized structure at the base of the follicle that helps orchestrate the growth cycle.

It is important to frame this as a description of a signaling pathway rather than a claim about any particular outcome. The receptor's activity translates a hormonal signal into changes in gene expression within the cell; how a given follicle responds to that signal depends heavily on the follicle's own genetically determined sensitivity, which is why the same circulating androgen levels affect different people, and different regions of the same person's scalp, so differently.

How DHT relates to anagen, catagen, and telogen

In follicles that are genetically sensitive to androgens, DHT signaling through the androgen receptor is associated with changes in the timing of the growth cycle. The most commonly described change is a gradual shortening of the anagen (active growth) phase. When anagen is shorter, the follicle spends less of each cycle actively building a hair shaft, and a larger share of follicles at any moment is found in the telogen resting phase relative to the growth phase.

Because the length a hair can reach depends on how long it stays in anagen, a progressively shorter growth phase is associated with hairs that emerge finer and shorter over successive cycles. This step-by-step change across repeated cycles is described as follicle miniaturization: with each turn of the cycle, an affected follicle tends to produce a thinner, less pigmented hair, and the ratio of growing to resting follicles in the affected area shifts. The catagen transition and telogen rest phases are still present, but the overall balance of the cycle tilts away from sustained growth.

This is a description of how the process is generally understood, not a timetable or a prediction for any individual. The pace and pattern of these changes vary widely from person to person, and many factors beyond androgens influence how a scalp looks over time. Whether and how this biology applies to a specific person is a clinical question for a licensed provider, not something an article can determine.

Why sensitivity varies from follicle to follicle

One of the most striking features of androgen biology in the scalp is that the same hormone is associated with opposite tendencies in different regions. In genetically susceptible follicles at the crown and hairline, androgen signaling is linked to miniaturization, while follicles in areas such as the back and sides of the scalp — and elsewhere on the body — can respond to androgens in the opposite direction. Researchers sometimes refer to this contrast as the androgen paradox, and it points to the fact that the hormone itself is not the whole story.

The difference comes down to the follicle's own genetically programmed characteristics: how much androgen receptor it expresses, how much 5-alpha-reductase activity is present locally, and the downstream signaling wired into that particular follicle. These traits are inherited and vary among individuals and among regions of the scalp, which is why pattern hair loss tends to follow recognizable distributions and why family history is often part of the clinical picture.

This variability is also why understanding the DHT pathway does not, by itself, tell anyone what is happening in their own scalp or what to do about it. Some prescription approaches to pattern hair loss are designed to act on parts of this pathway — for example, the enzymatic conversion of testosterone to DHT — while others act on the follicle through unrelated mechanisms. Whether any such approach is appropriate for a given person is a judgment that belongs to an independent licensed provider who can weigh that person's history and goals.

How prescription review works on OpenDoseRx

This article is educational and describes biology only; it is not medical advice and does not recommend any product, ingredient, or course of action for you. On OpenDoseRx, the clinical decision is made by a clinician rather than by the shopper. You begin by choosing a product and strength, then complete a medical intake that collects your health history and other relevant information.

That intake is routed to an independent, licensed U.S. provider who reviews it and decides whether a prescription is appropriate for you — a clinical judgment, not an automatic one. If the provider determines a prescription is appropriate, it is sent to a licensed U.S. pharmacy to be filled and shipped to you. If the request is declined, you are not charged for the medication and you receive a full refund.

Every product offered through OpenDoseRx is prescription-only, so nothing is prepared or shipped until that independent review is complete. And nothing here replaces a conversation with your own healthcare provider, who knows your full medical history and can address questions this kind of general education cannot.