The Science of Male Pattern Baldness: DHT, Follicle Miniaturization and What Actually Happens Over Time

What Is Male Pattern Baldness and What Causes It?

Male pattern baldness, also known as androgenetic alopecia, is the most common type of hair loss in men and people assigned male at birth. It develops gradually and usually follows a recognizable pattern, most often beginning with a receding hairline, thinning at the crown (or near the temples), or both.

It is also extremely common. Around 30% to 50% of men are affected by age 50, and up to 80% by age 70. Although many people think of it as something that only happens later in life, some men notice the first signs of balding at 20 or as early as their late teens.

It’s easy to blame everyday habits for hair loss, but male pattern baldness isn’t caused by hats, poor scalp circulation, hair products, or shampooing too often. It is influenced by a combination of factors, including:

• Hormones: especially dihydrotestosterone (DHT)
• Genetics: which affect which follicles are more vulnerable and how early the process begins
• Age: which can make the condition more noticeable over time

Aside from having a family history of male pattern baldness (especially on the maternal side), there are other risk factors that make some men more likely to experience the condition such as being Caucasian.

What Is the Normal Hair Growth Cycle?

If you want to understand how androgenetic alopecia happens, it helps to start with the normal hair growth cycle.

Your hair does not grow continuously, and male pattern baldness does not mean follicles suddenly stop working altogether. Each follicle moves through a repeating cycle of growth, transition, rest, and shedding.

• Anagen: The active growth phase, when the follicle produces thick, pigmented hair. On the scalp, this phase can last about two to six years. There are around 100,000 to 150,000 hair follicles on your scalp. Approximately 90% of those hairs are in the anagen phase at any given time.
• Catagen: The short transition phase, when growth stops. The follicle detaches from its blood supply and shrinks, but still retains the hair fiber (now called club hair). It lasts around two to three weeks.
• Telogen: The resting phase, when the club hair stays in place for a while before falling out, making room for a new growth. If you are wondering: “how long does the telogen phase last?” It usually lasts around two to four months.
• Exogen: The shedding phase, when the old hair falls out and a new hair emerges from the same follicle.

In male pattern baldness, the hair growth cycle time is altered, which changes how long hairs grow, rest, and shed

How Does DHT Affect Hair Follicles?

DHT is an androgen (male sex hormone) derived from testosterone through the action of an enzyme 5-alpha reductase (5-AR). It binds to receptors in the hair follicles, causing them to shrink (miniaturize) and diminishing their overall functions. It also shortens the growth phase of the hair cycle.

“If all men (and women) have DHT, why do some men not go bald?” you might ask. The answer is simple. DHT may be a primary cause of male hair loss, but its impact depends heavily on genetics.

Your genetics determine the amount of DHT you produce, but a high DHT level alone isn’t enough to cause hair loss. Genetic baldness happens when the follicles in certain areas of the scalp are genetically susceptible. So, rather than affecting every male and follicle equally, DHT’s impact depends on inherited sensitivity. That is why not every man experiences this form of hair loss in the same way, or at the same rate.

What Is Follicle Miniaturization?

Follicle miniaturization is the process that drives much of the visible hair thinning seen in male pattern balding. In androgenetic alopecia, genetically susceptible follicles under the influence of DHT gradually shrink. As this happens, they start producing hairs that are thinner, finer, and less pigmented than the surrounding hair.

The process is also closely tied to the hair growth cycle. It is characterized by a shorter anagen (growth) phase, longer telogen (resting) phase, and a prolonged period of an additional phase known as kenogen or “empty phase” where the follicle remains empty after a hair has shed. What this means is that hairs have less time to reach their usual length before shedding, and they take a while to regrow after shedding.

Over time, follicle miniaturization can make certain areas look less dense, even before a fully bald patch appears. That is why early male pattern baldness often shows up as reduced coverage, finer strands, or increased scalp visibility rather than sudden hair loss.

In men, follicle miniaturization usually becomes noticeable first at the temples, along the hairline, or at the crown, which are the areas most commonly affected by male pattern baldness.

What Happens Over Time in Male Pattern Baldness?

For many men, the early stage of male pattern baldness starts with slight recession at the temples, thinning around the hairline, or reduced density at the crown. Since these changes often happen slowly and unevenly, they can go unnoticed until hair loss becomes more obvious.

As the condition progresses, the affected areas may recede further and eventually merge, leaving hair mainly at the sides and back of the head in a U-shaped or horseshoe pattern.

One of the most widely used ways to describe hair loss progression in male pattern baldness is the Norwood scale (or Hamilton-Norwood scale), a gold-standard classification system for the 7 stages of hair loss.

The 7 stages of male pattern hair loss

Stage 1: Full head of hair. Little to no visible hair loss, and the hairline remains largely unchanged.

Stage 2: Mild recession begins at the temples as the hairline starts to mature. Male pattern baldness stage 2 is usually considered an early stage, and the change may still be subtle.

Stage 3: Recession becomes deeper and more noticeable, often creating the classic M-or V-shaped hairline associated with established male pattern baldness.

Stage 4: Frontal recession becomes more pronounced, and a distinct thinning area may begin to appear at the crown.

Stage 5: The frontal and crown thinning areas become larger, and the strip of hair separating them becomes thinner.

Stage 6: The frontal and crown areas of hair loss nearly merge, leaving much less coverage across the top of the scalp.

Stage 7: This is the most advanced stage, with only a narrow horseshoe-shaped ring of hair remaining at the sides and back of the head.

Although the Norwood scale does not explain the biology behind male pattern baldness or how to reverse it, it helps measure male hair loss severity and shows how the condition can progress over time. It is a great tool for people who track their hair journey visually and objectively.

Does Thinning Hair Mean Balding?

Not necessarily. Hair thinning doesn’t always mean you are balding, but it can be an early sign. Thinning means that your hair is losing density or volume. This can happen for many reasons, including chronic stress, tight hairstyles, nutritional deficiencies, hormonal changes, or certain medications.

Balding, on the other hand, is a more advanced, progressive type of hair loss that isoften driven by genetics. It happens when hair follicles gradually shrink and produce finer, weaker hairs over time. As this process continues without safe and effective treatment, some follicles may eventually stop producing hair.

Why Objective Hair Loss Tracking Matters

Male pattern baldness usually develops gradually. Because of that, it can be easy to miss early changes or misjudge how much hair loss is actually happening. Many men feel that their hair is “suddenly getting worse,” when in fact the change has been building over months.

Objective hair loss tracking helps remove some of that guesswork. It gives you a clearer way to monitor changes over time instead of relying only on memory, mood, or daily impressions.

It can help you:

• Detect thinning earlier
• See whether your hairline, temples, or crown are changing
• Compare progress over weeks and months
• Assess whether a treatment plan is helping, flatlining, or losing effectiveness
• Have better conversations with a dermatologist or hair-loss specialist

Objective tracking is also useful because hair can look different from day to day. Lighting, hair length, styling, wetness, and camera angles can all make the same scalp look denser or thinner than it really is. Without a consistent way to compare images, it is easy to overestimate or underestimate what is happening.

A better approach is to track hair loss under the same conditions each time. That usually means taking photos from the same angles, in similar lighting, with dry hair, and at regular intervals. Over time, this creates a more reliable record of whether the condition is progressing.

Hairloss AIis the first AI-powered mobile app designed for professional-grade alopecia tracking. Beyond standard photo tracking, it helps you assess hair loss more comprehensively by combining guided scans, Norwood stage estimation, density heatmaps, side-by-side comparison, and treatment logging in one place. This makes it easier to catch subtle changes sooner, see whether your treatment plan is actually helping, stay more consistent with your routine, and make decisions based on patterns you can track instead of guesses in the mirror.

References

1. How to treat androgenetic alopecia – the most common form of hair loss. A review. (n.d.). ResearchGate. https://www.researchgate.net/publication/381424860_How_to_treat_androgenetic_alopecia_-_the_most_common_form_of_hair_loss_A_review
2. Asfour, L., Cranwell, W., & Sinclair, R. (2023, January 25). Male androgenetic alopecia. Endotext - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK278957/
3. Urysiak-Czubatka, I., Kmieć, M. L., & Broniarczyk-Dyła, G. (2014). Assessment of the usefulness of dihydrotestosterone in the diagnostics of patients with androgenetic alopecia. Advances in Dermatology and Allergology, 4(4), 207–215. https://doi.org/10.5114/pdia.2014.40925
4. Kidangazhiathmana, A., & Santhosh, P. (2022). Pathogenesis of androgenetic alopecia. Clinical Dermatology Review, 6(2), 69–74. https://doi.org/10.4103/cdr.cdr_29_21
5. Redmond, L. C., Limbu, S., Farjo, B., Messenger, A. G., & Higgins, C. A. (2023). Male pattern hair loss: Can developmental origins explain the pattern? Experimental Dermatology, 32(7), 1174–1181. https://doi.org/10.1111/exd.14839