Hair loss has more than one cause, most common being telogen effluvium and androgenetic alopecia. They can occur independently, they can occur simultaneously, and they look similar to the untrained eye. Getting the diagnosis right is the starting point for getting the treatment right. This article explains what each condition is, how they differ, and why identifying the correct cause changes everything about the clinical approach.
The Hair Cycle and Its Phases
To understand both conditions, it helps to start with the hair cycle. Each hair follicle goes through three main phases:
Anagen (growth): The active phase where the hair grows. On the scalp, anagen typically lasts two to seven years. About 85–90% of scalp hairs are in anagen at any given time.
Catagen (regression): A brief transitional phase lasting two to three weeks. The follicle shrinks and the hair shaft detaches from its blood supply.
Telogen (resting): A resting phase lasting about 3 months. The hair sits in the follicle but does not grow. At the end of telogen, a new anagen hair pushes the old hair out. About 10–15% of scalp hairs are in telogen at any time.
Normal daily hair shedding (about 50 to 100 hairs per day) is a product of this cycling. Hairs entering telogen shed about 3 months later as the new anagen hair pushes them out.
Hair shedding is a normal and continuous process driven by the hair cycle. Abnormal shedding occurs when too many follicles shift to telogen simultaneously or when follicles fail to re-enter anagen after resting.
What Is Telogen Effluvium?
Telogen effluvium occurs when a significant proportion of anagen follicles are abruptly shifted into telogen simultaneously. Because telogen lasts about 3 months, the resulting shed typically occurs 2 to 4 months after the triggering event.
The shed is diffuse, affecting the entire scalp rather than following a pattern. It often presents as large amounts of hair in the shower drain, on the pillow, and throughout the day. Patients frequently describe finding hair everywhere.
Common triggers include:
Significant stress: Surgery, major illness, hospitalization, rapid weight loss, extreme caloric restriction
Hormonal shifts: Postpartum (one of the most common triggers), stopping hormonal contraceptives, thyroid dysfunction
Nutritional deficiencies: Iron, zinc, protein, and vitamin D deficiencies can all trigger telogen effluvium
Psychological stress: Severe or sustained psychological stress has been documented as a trigger, though the threshold required is significant
Medications: Certain medications including retinoids, anticoagulants, beta-blockers, and antidepressants can trigger shedding
Telogen effluvium is reactive hair loss caused by an identifiable trigger that disrupted the hair cycle. Identifying and treating the trigger is as important as any topical or oral treatment.
What Is Androgenic Alopecia?
Androgenetic alopecia is a genetically determined, hormonally driven condition. DHT progressively miniaturizes follicles that carry a genetic sensitivity to the hormone. The process happens slowly, over years and decades, and follows a predictable pattern. In men, the hairline recedes and the crown thins (Norwood classification). In women, the central part widens and the vertex thins while the frontal hairline is usually preserved (Ludwig classification).
Androgenetic alopecia does not have a trigger in the same way telogen effluvium does. It is the expression of a genetic predisposition that activates with hormonal maturity. It does not resolve on its own, meaning that without treatment, it progresses.
Androgenetic alopecia is chronic and progressive. Telogen effluvium is often acute and self-limiting. These are fundamentally different diseases despite producing overlapping symptoms.
How to Tell the Difference
Clinicians use several features to distinguish the two conditions:
- Pattern of loss:
- Telogen effluvium: diffuse, affecting the whole scalp more or less equally
Androgenetic alopecia: patterned, following the hairline and crown distribution in men; central part widening in women
Timing and trigger:
Telogen effluvium: often a clear onset 2 to 4 months after a known stressor, illness, or hormonal event
Androgenetic alopecia: gradual onset, often without a clear trigger, usually first noticed as thinning that has been developing for years
Pull test:
In active telogen effluvium, the pull test (gentle traction on 40–60 hairs) yields more than six shed hairs: a positive result indicating excess telogen activity
In stable androgenetic alopecia without concurrent shedding, the pull test is often negative
Scalp appearance and trichoscopy:
Androgenetic alopecia shows hair shaft diameter variability on trichoscopy. Reduced hair shaft diameter is a hallmark of miniaturization and early scalp visibility at affected areas
Telogen effluvium shows diffuse reduction in density without the diameter variability characteristic of miniaturization
The combination of pattern, timing, pull test, and trichoscopic findings usually distinguishes the two conditions with reasonable confidence. Laboratory work rules out nutritional and hormonal contributors.
When Both Conditions Are Present
Telogen effluvium and androgenetic alopecia frequently occur at the same time, particularly in women. A woman with genetic susceptibility to androgenetic alopecia who experiences a postpartum shed or a period of considerable stress may present with hair loss that looks more severe than either condition alone would produce.
This overlap is crucial because it changes the treatment approach. Addressing only the androgenetic alopecia without identifying and correcting the telogen effluvium trigger leaves one driver untreated. Addressing only the telogen effluvium trigger and not the underlying androgenetic alopecia leads to disappointment when the hair does not fully recover after the trigger resolves.
When both conditions are present, both require attention. A thorough evaluation should screen for nutritional deficiencies, hormonal contributors, and medication side effects even in a patient with a clearly established androgenic pattern. Treatment Implications
For telogen effluvium:
Identify and address the trigger. Restore nutritional deficiencies, manage thyroid dysfunction, review medications.
Support the recovery period. Adequate protein intake, micronutrient optimization.
In most cases, hair will recover within 6 to 12 months once the trigger is addressed.
If shedding persists beyond 12 months without an identifiable cause, chronic telogen effluvium should be considered and investigated.
For androgenetic alopecia:
- DHT suppression (finasteride or dutasteride) and/or minoxidil as primary treatments.
Long-term maintenance. The condition does not resolve and treatment must continue to preserve results.
Telogen effluvium often improves without specific hair loss treatment once the trigger is resolved. Androgenetic alopecia requires ongoing treatment. Distinguishing between them prevents both undertreatment and unnecessary long-term medication. Summary
Telogen effluvium is diffuse, reactive hair loss triggered by physiological or nutritional stressors that shift follicles into the resting phase. Androgenetic alopecia is genetically determined, patterned, progressive loss driven by DHT. They are distinguished by their pattern, timing, pull test results, and trichoscopic findings. They frequently co-exist, particularly in women, and both require attention when present simultaneously. Correctly identifying the condition or combination of conditions is the essential first step in building an appropriate treatment plan.