The hormone behind male pattern baldness.
Most people know that hair loss is genetic, but fewer understand the specific mechanism that causes it. The answer comes down to a single hormone: DHT, or dihydrotestosterone.
DHT is derived from testosterone. An enzyme called 5-alpha reductase converts testosterone into DHT in various tissues throughout the body, including the scalp. For most bodily functions, DHT is unremarkable. But in men who are genetically predisposed to hair loss, DHT causes a damaging process in the scalp called follicle miniaturisation.
What follicle miniaturisation means.
Hair follicles go through cycles: a growth phase (anagen), a transition phase (catagen), and a resting phase (telogen). In a healthy scalp, follicles spend most of their time in the growth phase, producing thick, long hairs.
When DHT binds to androgen receptors in genetically sensitive follicles, it shortens the growth phase with each successive cycle. The follicles produce progressively thinner and shorter hairs until eventually the growth phase is so short that no visible hair is produced at all.
This process happens gradually over years and decades. It's why hair loss looks different at 25 versus 45 — the same process, just further along.
Why genetics determine sensitivity.
Not all men are equally sensitive to DHT. The number of androgen receptors in your follicles, and how sensitive those receptors are to DHT, is genetically determined. This is why some men can have high testosterone levels and never lose their hair, while others experience significant loss by their mid-twenties.
The genetic factors come from both sides of your family — it's not simply a matter of looking at your maternal grandfather, as the old myth suggests. If either parent's family has a history of hair loss, your risk is elevated.
The key takeaway: Hair loss is not caused by high testosterone. It's caused by genetic sensitivity to DHT — a byproduct of testosterone. You can have average testosterone levels and still experience significant hair loss if your follicles are sensitive.
How finasteride works against DHT.
Finasteride works by inhibiting the 5-alpha reductase enzyme that converts testosterone into DHT. By blocking this conversion, finasteride reduces scalp DHT levels by approximately 60-70% — enough to halt the miniaturisation process at its source rather than simply managing the symptoms.
This is why finasteride is considered the most effective single treatment for male pattern hair loss. It addresses the root cause rather than working around it.
Minoxidil works through a complementary mechanism — it doesn't affect DHT at all, but instead directly stimulates follicle activity and improves blood flow and oxygen delivery to the scalp. Used alongside finasteride, minoxidil helps reactivate follicles that have already been affected while finasteride prevents further damage. The combination produces significantly stronger results than either treatment alone.
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