How DHT Causes Hair Loss

What Is DHT?

Dihydrotestosterone (DHT) is an androgen hormone derived from testosterone through the action of the enzyme 5-alpha reductase. While DHT plays important roles during puberty — driving the development of male secondary sex characteristics like facial hair and voice deepening — it becomes a liability for scalp hair in genetically predisposed individuals. DHT is approximately five times more potent than testosterone at binding to androgen receptors, making it a powerful hormonal signal.

How DHT Damages Hair Follicles

In men with androgenetic alopecia, certain hair follicles on the scalp (particularly at the temples and crown) express high levels of androgen receptors. When DHT binds to these receptors, it triggers a process called follicular miniaturization. The growth (anagen) phase of the hair cycle becomes progressively shorter, while the resting (telogen) phase lengthens. Over successive cycles, the follicle produces thinner, shorter, and less pigmented hairs until it eventually stops producing visible hair altogether.

The Genetic Component

Not everyone with normal DHT levels experiences hair loss. The key factor is genetic sensitivity — specifically, the density and responsiveness of androgen receptors in scalp follicles. This genetic predisposition is polygenic, meaning multiple genes contribute, and it can be inherited from either parent. The androgen receptor gene on the X chromosome is one of the strongest genetic predictors, but it is far from the only factor.

Why the Hairline Pattern?

The characteristic pattern of male hair loss — receding temples and thinning crown — occurs because follicles in these regions express the highest density of androgen receptors. Follicles at the back and sides of the scalp (the occipital region) are genetically programmed to be DHT-resistant, which is why they persist even in advanced baldness. This differential sensitivity is also why transplanted follicles from the occipital region retain their DHT resistance in their new location.

Implications for Treatment

Understanding the DHT mechanism directly informs treatment strategy. The most effective medical treatments — finasteride and dutasteride — work by inhibiting 5-alpha reductase to reduce DHT production. Minoxidil works through a separate mechanism (vasodilation and potassium channel opening) and can be combined with DHT blockers for synergistic results. Early intervention is critical because once a follicle is fully miniaturized, it is much harder to reverse than simply maintaining a weakened but still-active follicle.