What is Telogen Effluvium?
Yes, telogen effluvium (TE) means increased shedding specifically during the telogen (resting) phase of the hair cycle—it occurs when a significant number of hair follicles prematurely enter telogen, resulting in excessive hair loss typically 3-4 months after a triggering event 1, 2, 3.
Understanding the Mechanism
The hair growth cycle consists of three phases:
- Anagen (growth phase): Normally lasts 2-7 years
- Catagen (transition phase): Brief, lasting 2-3 weeks
- Telogen (resting phase): Lasts about 3 months before the hair sheds
In normal scalp, approximately 85-90% of hairs are in anagen and only 7-10% are in telogen 1. In telogen effluvium, this ratio shifts dramatically—more follicles enter telogen prematurely, increasing the percentage of telogen hairs to >10% 1.
Why the Delayed Shedding?
The characteristic 3-4 month delay between the triggering event and visible hair loss occurs because hairs must complete their telogen phase before they shed 3. This is why patients often struggle to identify the cause—the trigger happened months before they noticed the problem.
Clinical Presentation
TE presents as diffuse scalp hair thinning with generalized persistent shedding across the entire scalp, including the occiput 1. This is a critical distinguishing feature:
- Positive hair pull test from multiple scalp areas (>2-3 hairs per pull of 50-60 hairs) 1
- No pattern distribution (unlike female pattern hair loss which spares the occiput) 1
- No miniaturization of hair shafts—the terminal-to-vellus hair ratio remains normal at approximately 9:1 1
- Preserved follicular ostia (no scarring) 1
Five Functional Types
Recent understanding recognizes five distinct mechanisms by which TE can occur 4:
- Immediate anagen release: Abrupt shift from anagen to telogen
- Delayed anagen release: Prolonged anagen followed by synchronized telogen entry
- Short anagen syndrome: Constitutionally shortened anagen phase
- Immediate telogen release: Premature shedding of telogen hairs
- Delayed telogen release: Prolonged telogen followed by synchronized shedding
Common Triggers
Look for these specific precipitants 3-4 months before hair loss onset 2, 5, 3:
- Physiological stress: Childbirth, major surgery, severe illness, high fever
- Nutritional: Sudden weight loss, crash dieting, low protein intake
- Medications: Beta-blockers, carbamazepine, vitamin A excess 6
- Endocrine: Thyroid dysfunction, hormonal changes
- Psychological stress: Major life events, emotional trauma
Important Caveat on Anesthesia
Surgery and anesthesia can trigger TE exacerbations—one case report documented significant hair loss over several months following surgical procedures in a patient with pre-existing TE 6. Consider this when counseling patients with TE history before elective procedures.
Diagnostic Approach
The diagnosis is primarily clinical 1:
- Hair pull test: Perform in multiple areas including occiput—positive if >2-3 hairs per pull 1
- Dermoscopy: Look for preserved follicular ostia, absence of miniaturization 1
- Scalp biopsy (if diagnosis uncertain): Shows increased telogen hairs (>10%) but normal terminal-to-vellus ratio (7-9:1) 1
Laboratory workup should target suspected triggers 7:
- Thyroid function tests (TSH, free T4)
- Complete blood count (hemoglobin)
- Ferritin (though recent evidence questions routine iron testing 7)
- Vitamin B12
- Consider zinc levels (found significantly lower in chronic TE 7)
Critical Distinction from Pattern Hair Loss
If hair pulls are positive only in affected areas (not occiput) and you see miniaturization, suspect female pattern hair loss with concurrent TE rather than isolated TE 1. This distinction fundamentally changes management.
Prognosis and Recent Insights
TE is generally self-limited with high remission rates once the trigger is removed 2. However, emerging research suggests TE may be a precursor to androgenetic alopecia in men—anagen shortening (manifesting as TE) appears to precede follicular miniaturization by years 8. This challenges the traditional view that these are entirely separate entities.
Chronic TE (CTE) persists beyond 6 months and requires more aggressive investigation for ongoing triggers 1.