Telogen Effluvium or Androgenetic Alopecia? How to Tell Different Types of Hair Loss Apart

"My hair is falling out" is a complaint that can hide at least two fundamentally different biological processes. Telogen effluvium (TE) is a reactive, usually temporary, increase in hair shedding triggered by metabolic stress on the body — illness, diet, childbirth, severe psychological stress, or a change in medication. Androgenetic alopecia (AGA) is a progressive, genetically determined miniaturization of hair follicles driven by testosterone derivatives, leading to permanent thinning in a characteristic pattern.

The distinction has enormous practical significance: telogen effluvium resolves on its own in the vast majority of cases once the trigger is removed, whereas androgenetic alopecia progresses over years without treatment. A treatment effective for one type (e.g., drugs that block DHT, used in AGA) makes no pharmacological sense in classic, isolated telogen effluvium — which is why correctly identifying the type of hair loss before looking for a solution is a step worth not skipping.

Each hair follicle independently goes through a cycle of three phases: anagen (the growth phase, usually lasting 2-7 years, in which about 85-90% of scalp hair is found at any given time), catagen (a brief transitional phase lasting a few weeks), and telogen (a resting phase lasting about 2-3 months, after which the hair falls out and the follicle eventually begins a new anagen cycle). Under normal conditions, because individual follicles are in different phases of the cycle independently of one another, losing 50-100 hairs a day is a normal, unnoticeable phenomenon.

Telogen effluvium happens when, under the influence of a strong stressor, a much larger percentage of follicles than usual becomes simultaneously "synchronized" and prematurely shifts from anagen to telogen. Because this happens at the same time in a large number of follicles at once, the effect — increased shedding — appears only about 2-3 months after the triggering event itself, when those synchronized follicles simultaneously finish their resting phase and release their hairs.

Androgenetic alopecia doesn't involve mass, simultaneous synchronization of the cycle, but rather the gradual miniaturization of genetically predisposed hair follicles under the influence of dihydrotestosterone (DHT) — a testosterone derivative with a stronger affinity for androgen receptors in the follicle. With each successive cycle, the affected follicle produces an increasingly thinner, shorter hair, until it eventually stops producing a visible terminal hair, replacing it with a thin, fine hair (vellus hair). This process is slow but — without intervention — progressive, and its pattern is genetically determined, which is why there are typical, predictable areas of density loss.

The pull test is performed by gently grasping a bundle of about 40-60 hairs close to the scalp and pulling it with steady, moderate pressure along the length of the hair. The result is considered positive when more than about 10% of the pulled hairs come out (a threshold of more than 6 hairs from the bundle is usually used). In telogen effluvium, the test is usually clearly positive across the entire scalp, reflecting the mass shift of follicles into the telogen phase. In androgenetic alopecia, the result is often negative or only weakly positive, because the miniaturization process doesn't increase the percentage of hairs in the shedding phase at any given moment as much.

The large retrospective study described above suggests that nutritional deficiencies are common in women with telogen effluvium, but not every study reaches identical conclusions — it's worth stating this honestly, rather than presenting the topic as fully settled.

Before reaching for a specific product or therapy for hair loss, it's worth first determining what type of problem you're dealing with — that's a single diagnostic decision that genuinely changes what comes next. Telogen effluvium mainly requires finding and removing the trigger, along with patience, while androgenetic alopecia requires a conscious decision about long-term treatment, described in detail in our separate articles on specific therapies.