Androgenetic and telogen hair loss

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Hair loss history begins with the event the person notices: handfuls of shed hair, a widening part, recession, a visible scalp under bright light or reduced ponytail volume. Androgenetic alopecia gradually shortens anagen and miniaturises susceptible follicles in a genetically determined distribution. Telogen effluvium increases the proportion of resting hairs across the scalp, creating relatively uniform shedding without destroyed follicles. Photographs taken years apart and dermoscopic shaft-diameter variation help separate slow miniaturisation from an acute shed.

A trigger for telogen effluvium usually precedes shedding by several months because follicles must move through catagen and telogen before release. Severe infection, operation, childbirth, iron deficiency, thyroid disease, marked energy restriction and medicine change are common contexts. Chronic shedding beyond six months needs review of persistent triggers, diagnostic uncertainty and overlap with female-pattern loss. Ferritin interpretation should reflect laboratory range, inflammation, blood loss and symptoms rather than a universal hair-growth threshold.

Treatment goals differ. Telogen effluvium care removes or corrects a cause and supports recovery; medication is not routinely required. Pattern loss treatment slows progression and may produce partial regrowth only while continued. Before commercial transplantation, platelet products or supplements, establish diagnosis and explain evidence, cost and the need to stabilise ongoing loss.

Key points

Androgenetic alopecia is gradual patterned miniaturisation: frontal and vertex recession is typical in male-pattern loss, while female-pattern loss often widens the central part with relative frontal-hairline preservation.
Telogen effluvium is diffuse shedding after many follicles synchronously enter rest, often two to three months after fever, surgery, childbirth, major psychological stress, dietary restriction or a medicine change.
Pattern loss and telogen effluvium can coexist; a shedding episode may reveal previously subtle miniaturisation rather than creating permanent follicle destruction.
Ask about onset, tempo, shedding versus thinning, pregnancy, illness, weight change, diet, menstruation, medicines, family pattern and hair practices before ordering tests.
Examine scalp and follicular openings, compare shaft diameters with dermoscopy and perform a standardised hair pull; inflammation or scarring overrides an ordinary pattern diagnosis.
Full blood count, ferritin and thyroid function are selected from diffuse-loss history and clinical risk; normal results do not justify repeated supplements or broad endocrine panels.
Licensed topical minoxidil can slow patterned loss but requires continued use, may cause early shedding and scalp irritation, and must not be applied in pregnancy or to inflamed skin.
Oral finasteride 1 mg is licensed for male-pattern hair loss in eligible men; discuss sexual and psychiatric adverse effects, pregnancy handling and the MHRA patient alert before prescribing.
Acute telogen effluvium commonly recovers after its trigger resolves, but shedding can continue for months and visible density lags behind renewed growth.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Inherited androgen sensitivity

Genetic susceptibility makes scalp follicles respond to dihydrotestosterone with progressive miniaturisation in a characteristic distribution after puberty.

Systemic telogen trigger

Fever, surgery, childbirth, endocrine disturbance, nutritional deficit or marked psychological stress can synchronise many follicles into resting phase.

Medicine-related cycling

Starting, stopping or changing selected retinoids, anticoagulants, beta blockers, anticonvulsants or hormonal medicines can contribute to diffuse shedding.

Combined mechanisms

A telogen episode can coexist with genetically patterned loss, making previously compensated miniaturisation suddenly visible after overall density falls.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Follicles progressively miniaturise
Successive androgen-sensitive cycles become shorter and produce finer, shorter shafts until scalp coverage decreases despite retained follicular units.
2
Follicles synchronise into rest
A systemic trigger shifts an unusually large cohort from anagen toward telogen, but release occurs only after the normal delay.
3
Club hairs are released
Resting hairs detach from across the scalp, producing dramatic washing and brushing loss without focal destruction or necessarily reduced new growth.
4
Recovery requires new length
Once the trigger resolves, follicles return to anagen, but months are needed before short fibres contribute appreciably to visible volume.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Frontal and vertex miniaturisation

Bitemporal recession and reduced vertex density with variable-calibre hairs support a male-pattern androgen-sensitive distribution.

Widening central part

Reduced density over crown with a broader part and relative preservation of the frontal hairline supports female-pattern loss.

Diffuse shedding

Increased full-length club hairs from across the scalp with preserved openings and no focal inflammation suggests telogen effluvium.

Delayed trigger relationship

A febrile illness, operation, childbirth, abrupt weight loss or new medicine two to three months before onset fits the follicular-cycle delay.

Regrowth halo

Short tapered hairs of similar length throughout the scalp after shedding indicate synchronised recovery rather than continuing shaft breakage.

Red flags requiring action

Loss of follicular openings, scalp pain or scale, pustules, rapid virilisation, a scalp mass, systemic illness, profound nutritional compromise or hair loss in a child requires an alternative and sometimes urgent specialist pathway.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Patterned scalp examination and trichoscopyFirst step
Why
Identify distribution, shaft miniaturisation, regrowth and inflammatory or scarring signs.
Interpretation and limitations
Hair-shaft diameter diversity in a patterned field supports androgenetic loss; uniform short regrowth supports recovering telogen effluvium, while lost openings require referral.
02
Standardised hair-pull test
Why
Assess active shedding across several scalp zones.
Interpretation and limitations
An increased proportion of released club hairs supports active telogen shedding but varies with washing and technique; a negative result between episodes does not exclude the history.
03
Full blood count and ferritin
Why
Detect iron deficiency or anaemia when diffuse loss, menstruation, diet or blood loss makes it plausible.
Interpretation and limitations
Interpret ferritin with inflammation and laboratory range and find the cause of deficiency; supplementation without deficiency exposes harm and does not treat pattern miniaturisation.
04
Thyroid function
Why
Identify thyroid dysfunction when diffuse shedding or systemic symptoms support testing.
Interpretation and limitations
Both hypo- and hyperthyroidism can affect hair; borderline results need thyroid-context interpretation rather than being declared the sole cause automatically.
05
Androgen and reproductive assessment
Why
Investigate rapid female-pattern loss accompanied by hirsutism, acne, cycle disturbance or virilisation.
Interpretation and limitations
Use a reliable testosterone pathway and selected PCOS or tumour tests; ordinary patterned loss without androgen features does not need a broad hormone panel.
06
Scalp biopsy
Why
Resolve persistent diffuse loss when clinical and dermoscopic assessment cannot distinguish miniaturisation, immune loss or early scar.
Interpretation and limitations
Dermatology selects a representative active site and orientation; biopsy has sampling limits and creates a permanent small scar.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Alopecia areata incognita

Diffuse immune-mediated shedding may show yellow dots, dystrophic hairs or evolving patches and can require specialist trichoscopy or biopsy.

Scarring alopecia

Perifollicular scale, pain, pustules, shiny skin or loss of openings indicates destructive inflammation rather than ordinary cycling or miniaturisation.

Tinea capitis

Scale, lymph nodes, black dots and broken or comma hairs support fungal shaft infection and require mycology plus systemic treatment.

Traumatic shaft breakage

Chemical, heat, tension or manipulation leaves hairs at varied lengths without the full-length club roots typical of telogen shedding.

Androgen excess disorder

Rapid patterned loss with hirsutism, acne, irregular cycles or virilisation requires endocrine assessment beyond ordinary inherited miniaturisation.

Additional chapter-specific clues

Alternative-diagnosis warningRed flag

Smooth patches, broken hairs of uneven length, perifollicular scale, pustules or missing openings require alopecia areata, trauma, fungus or scar assessment.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Diffuse sheddingReconstruct the follicular timelineFirst stepHair is shedding from the whole scalp without obvious scar or focal inflammation.

1Map onset against illness, operation, childbirth, medicines, menstruation, dietary restriction and psychological stress during the preceding two to four months.
2Examine for patterned miniaturisation and regrowth, then request full blood count, ferritin, thyroid or other tests only where history creates a plausible corrective action.
3Treat the identified cause, support adequate nutrition and review over six to twelve months, explaining that shedding and visible density recover on different timelines.

02Patterned lossOffer evidence-based maintenance treatmentGradual distribution and shaft miniaturisation support androgenetic alopecia.

1Document baseline distribution with consented photographs and assess blood pressure, scalp disease, pregnancy plans and medicines before treatment.
2Offer a licensed sex-specific topical minoxidil formulation, or discuss finasteride 1 mg with an eligible man after MHRA psychiatric, sexual and reproductive counselling.
3Review application, adverse effects and photographs after at least six months; continue only when benefit and burden remain acceptable because gains recede after stopping.

03Mixed patternTreat shedding and miniaturisation separatelyAn acute telogen trigger has exposed underlying central or vertex thinning.

1Name both processes and correct the telogen trigger without promising that this alone reverses established miniaturisation.
2Allow scalp irritation to settle, then consider pattern-loss treatment according to licence and preference while normal regrowth proceeds.
3Compare serial photographs and hair calibre, separating reduction in shower shedding from slower change in crown density.

04Uncertain or progressiveEscalate before irreversible lossEscalationInflammation, loss of openings, rapid progression, virilisation or treatment failure makes the working diagnosis unsafe.

1Stop irritant commercial products and perform focused fungal, endocrine or inflammatory investigations from the clinical pattern.
2Refer urgently when scarring signs, rapid virilisation, severe systemic illness or a mass is present; otherwise seek routine dermatology for trichoscopy or biopsy.
3Do not proceed to transplantation until the diagnosis is secure and any inflammatory or progressive process has been stabilised.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

Prolongs anagen and can slow progression or improve density while continuously used for male-pattern hair loss.

Minoxidil 5% foam for licensed male-pattern use

Apply half a capful to the dry affected scalp twice daily, do not exceed a total of two capfuls daily, and wash hands afterwards.

Use only on a healthy scalp and stop for chest pain, faintness, tachycardia, oedema or persistent irritation. Avoid pregnancy and breastfeeding, prevent transfer to other skin and keep away from flame while wet.

Supports density in licensed female-pattern hair loss when used continuously over an adequate trial.

Minoxidil 5% foam for licensed female-pattern use

Apply half a capful to the dry affected scalp once daily, allow it to dry fully and wash hands after application.

Exclude sudden unexplained loss and scalp inflammation first. Avoid pregnancy and breastfeeding; counsel about early shedding, unwanted facial hair, irritation and loss of benefit after discontinuation.

Reduces dihydrotestosterone-driven follicular miniaturisation in licensed male-pattern hair loss.

Finasteride 1 mg

Eligible adult men take 1 mg by mouth once daily; assess benefit only after at least three to six months of continuous treatment.

Discuss depression, suicidal thoughts and sexual dysfunction including possible persistence, supply the MHRA patient alert and stop urgently for serious mood change. It is not for pregnancy; pregnant people must not handle crushed or broken tablets, and PSA interpretation changes.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Progressive visible thinning

Untreated androgenetic miniaturisation advances variably and can leave too little donor or native density for satisfactory later restoration.

Chronic shedding anxiety

Repeated counting, photographing and checking can amplify distress even while follicular recovery is biologically proceeding normally.

Medicine adverse effects

Minoxidil can cause irritation, unwanted hair and cardiovascular symptoms, while finasteride has important psychiatric, sexual and reproductive harms.

Unnecessary treatment burden

Unproven supplements, tests, injections and commercial procedures create cost and toxicity when diagnosis and modifiable triggers were never established.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Compare standardised part, temples, vertex and hairline photographs after six and twelve months rather than relying on daily shedding counts.
Review minoxidil application amount, scalp irritation, dizziness, palpitations, oedema and unwanted facial hair, including accidental transfer from hands or pillows.
At finasteride reviews ask directly about mood, suicidal thoughts and sexual effects and revisit ongoing benefit, fertility questions and PSA implications.
Confirm that an iron, thyroid, nutritional or medicine trigger has been corrected and investigate continued shedding beyond the expected recovery interval.
Re-examine follicular openings and scalp inflammation whenever loss changes character, because an early scarring process can initially look diffuse.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

The shed is delayed

Telogen hair remains anchored for weeks after its growth phase ends, so the trigger often predates visible shedding by two to three months.

Density lags shedding

Shower loss may normalise before new fibres are long and thick enough to restore coverage, creating a discouraging but expected interval.

Two diagnoses often overlap

Acute shedding reduces volume everywhere and exposes crown miniaturisation that had developed slowly, so one history can contain both mechanisms.

Minoxidil requires continuity

Initial shedding can occur as follicles change cycle, while any sustained benefit generally recedes after treatment is stopped.

Supplements need a deficit

Iron and micronutrients correct documented deficiency; supraphysiological use can cause toxicity and does not reverse genetically patterned miniaturisation.

11Common pitfallsFrequent interpretation and management errors.

01
Attributing a shed to the most recent event when the relevant trigger often occurred months earlier.
02
Ordering broad nutritional and hormone panels without a history that makes the result actionable.
03
Prescribing iron indefinitely for a normal ferritin or without investigating the reason for deficiency.
04
Using one generic minoxidil instruction despite sex-specific product licences and different application frequencies.
05
Prescribing finasteride without explicit psychiatric, sexual and pregnancy-handling counselling.
06
Calling every diffuse loss telogen effluvium while missing inflammation or disappearing follicular openings.