Understanding Androgenetic Alopecia, the “Hereditary Baldness”

Androgenetic alopecia is the most common form of progressive hair loss, affecting both men and women, though it manifests differently between the sexes. It results from a complex interaction of genetics, hormones (particularly androgens), and local factors within the hair follicle.

Main Mechanism: The Role of Hormones and Follicular Sensitivity

At the core of the process lies the action of dihydrotestosterone (DHT), a hormone derived from the conversion of testosterone by the enzyme 5α-reductase. DHT binds to androgen receptors located in hair follicles, especially in those that are genetically predisposed to sensitivity.

Over time, under the influence of this hormonal stress, several changes occur:

The hair growth cycle (anagen → catagen → telogen) shortens, the anagen or “growth” phase becomes briefer.
Follicles gradually shrink, a process known as follicular miniaturization. This leads to thinner, less pigmented hair and, in severe cases, the eventual disappearance of the active follicle.
Mild inflammation, oxidative stress, and reduced microcirculation can further aggravate the process locally.

The degree to which a follicle reacts to DHT depends on genetic variations. Some individuals express more androgen receptors, or possess cofactors that amplify the DHT response.

Why Women Do Not Experience “Male-Pattern Baldness”

A common question arises: if androgenetic alopecia also affects women, why do they not experience baldness in the same way men do?

Several factors explain this difference:

Lower overall androgen levels: women produce less testosterone, and therefore less circulating DHT.
Different hormonal distribution: the activity of 5α-reductase, the ratio of androgens to estrogens, and other hormones such as thyroid hormones influence DHT’s impact.
Reduced follicular sensitivity in certain areas: follicles on the top of the female scalp are often less responsive to DHT, or the effect is more diffuse.
Genetic and chromosomal factors: certain genes alter androgen sensitivity, and some of these genes vary by sex. Because women inherit genes carried on the X chromosome, their androgen response may differ significantly.
Diffuse rather than localized thinning: in women, hair loss usually appears as an overall reduction in density, centered on the crown, without a pronounced receding hairline.

In practice, this means that male-pattern baldness, with sharply defined bald areas and a receding hairline, is rare among women. Female-pattern hair loss usually presents as gradual thinning and a widening part.

Signs, Onset, and Stabilization of Hair Loss

When Does Hair Loss Begin and How Does It Progress?

In men, the first signs of androgenetic alopecia can appear as early as their twenties, such as a subtle retreat of the hairline, temple thinning, or reduced density on the crown. Over time, this follows the Norwood scale, which classifies the stages from I to VII.

In women, onset can occur at any age, but is more common around menopause when hormonal fluctuations play a role. The process is often gradual, with a noticeable reduction in density, a widening part, or increased scalp visibility at the top of the head.

At What Age Does Hair Loss Stabilize?

One frequently asked question is at what age baldness tends to stabilize. According to studies, androgenetic hair loss tends to slow down, or partially stabilize, between ages 30 and 45 for many individuals. However, this stabilization is relative and depends on genetics, androgen levels, aggravating factors, and the stage of progression.

This does not mean the loss stops completely, it may continue at a slower rate or fluctuate with internal and external influences such as stress, nutritional deficiencies, or hormone therapy. This phase is often when changes become less dramatic, making it easier to plan long-term interventions such as hair transplants on more stable areas.

Other Causes of Hair Loss: Understanding the Differences

Before concluding that one has androgenetic alopecia, it is important to distinguish it from other types of hair loss:

Telogen effluvium (stress or seasonal shedding): a diffuse and temporary shedding triggered by a shock such as hormonal change, nutrient deficiency, or acute stress. It typically lasts four to six weeks and then subsides.
Chronic non-androgenetic hair loss: sometimes linked to inflammation, dermatitis, nutritional deficiency, or endocrine issues.
Alopecia areata or scarring alopecia: these forms have distinct clinical patterns, often patchy or permanent, and require medical diagnosis.
Aggravating factors: iron deficiency, vitamin imbalances, hormonal disorders involving the thyroid or androgens, tight hairstyles, chronic stress, or smoking.

Proper identification of the type of hair loss is crucial, as it determines the most effective treatment approach and potential outcomes.

Why Some People Lose Hair Earlier or More Intensely

Several variables explain why the severity and timing of hair loss differ so much between individuals:

Genetic heritage: some people inherit highly sensitive androgen receptors, or genes that regulate hormonal response at the follicular level.
Hormonal load: higher androgen levels, or increased local conversion of testosterone to DHT, can accelerate the process.
Scalp condition: chronic inflammation, poor microcirculation, oxidative stress, and environmental factors all play a role.
Age and cellular wear: as we age, follicular repair and regeneration mechanisms become less efficient.
External and lifestyle factors: diet, sleep, stress, smoking, harsh hair treatments, and overall health can influence progression.
Follicular reserve threshold: a person’s initial follicle density provides a kind of safety margin before miniaturization becomes visible.

In Summary

Androgenetic alopecia is a multifactorial condition in which hormones, especially DHT, and genetic follicular sensitivity play a central role.
Women experience it differently from men, their loss is usually more diffuse and less localized because of lower androgen levels and reduced follicular sensitivity.
Hair loss often begins in the twenties or thirties, but the rate of thinning tends to slow down or partially stabilize between ages 30 and 45.
It is essential to distinguish androgenetic alopecia from other causes of hair loss such as telogen effluvium, dermatitis, or nutritional deficiencies in order to choose the right approach.
Finally, individual variability is significant, two genetically predisposed people may experience very different outcomes depending on both internal and external factors.