Lesson
Read Hair Loss Through the Follicle Cycle
Hair loss can reflect shortened growth, synchronized rest, matrix injury, shaft breakage, miniaturization, or follicular destruction. The cycle explains why cause and shedding may be separated by months.
- Anagen
- Catagen
- Telogen
- Exogen
- Miniaturization
Long duration defines scalp length
Matrix activity contracts
The club hair remains retained
Shedding can lag a trigger by months
Follow active growth
Anagen is the long growth phase. Matrix cells divide rapidly, so severe metabolic stress and cytotoxic therapy can interrupt growth quickly.
Account for delayed shedding
A trigger can push follicles into telogen, but visible shedding often begins weeks to months later. The delay can obscure the causal event.
Separate shedding from breakage
A shed club hair differs from a broken shaft. Chemical processing, heat, friction, tension, and structural disease can reduce length without releasing the follicle.
Recognize miniaturization and destruction
Androgenetic alopecia gradually converts terminal hairs into finer hairs. Scarring alopecia destroys follicles and may erase follicular openings, making delay costly.
Quick check
Lesson
Classify the Pattern Before Treating
Tempo, geometry, inflammation, symptoms, breakage, follicular openings, nail findings, body-hair involvement, exposures, and systemic context define the differential.
- Patterned thinning
- Diffuse shedding
- Patchy loss
- Scalp inflammation
- Follicular openings
Dandruff is the mild scalp end
Vehicle and steroid risk change
Hair loss or pustules change the diagnosis
Do not self-treat a dangerous pattern
Central, crown, or frontal geometry
Trigger history is central
Examine hairs, skin, and nails
Early treatment protects remaining follicles
Build the chronology
Document onset, progression, shedding, illness, surgery, childbirth, weight change, diet, stress, medication changes, styling, family history, and associated symptoms.
Examine beyond density
Inspect scalp scale, erythema, pigment, pustules, scarring, hair caliber, broken hairs, pull pattern, brows, lashes, body hair, and nails.
Order targeted tests
Laboratory testing should answer a clinical hypothesis such as thyroid disease, anemia, iron deficiency, nutritional deficiency, or androgen excess. Broad supplement panels without context create noise.
Escalate red flags
Pain, burning, pustules, boggy inflammation, rapid focal loss, broken hairs, eyebrow loss, absent follicular openings, or systemic illness needs diagnostic evaluation.
Quick check
Lesson
Connect DHT to Follicular Miniaturization
Androgenetic alopecia is genetically patterned and progressive. Local androgen metabolism and follicular sensitivity shorten anagen and produce finer, shorter hairs.
- Five alpha reductase
- DHT
- Androgen receptor
- Miniaturization
- Pattern
Five alpha reductase supplies the signal
Susceptibility differs by follicle
Terminal hairs become finer
Maintenance preserves response
Map the enzyme signal
Five alpha reductase converts testosterone to dihydrotestosterone. Finasteride preferentially inhibits the type 2 isoenzyme and lowers DHT signaling in susceptible follicles.
Read pattern without stereotype
Men often develop frontal, temporal, vertex, or crown loss. Women often show central thinning or a widening part, but pattern alone does not replace examination and endocrine context.
Set realistic goals
Treatment can slow progression and increase thickness, but complete restoration is uncommon. Earlier miniaturization is more reversible than long-standing follicular loss.
Separate approved and clinician-directed use
Topical minoxidil has labeled products for men and women. Finasteride 1 mg is labeled for male pattern hair loss in men only, while other uses require specialist judgment.
Quick check
Lesson
Use Topical Minoxidil as a Product, Not a Class Shortcut
Topical minoxidil requires follicular activation to minoxidil sulfate and sustained scalp exposure. Strength, vehicle, labeled population, dose, and schedule differ among products.
- Minoxidil sulfate
- Potassium channels
- Solution
- Foam
- Continued use
Product-specific dose and schedule
Follicular sulfotransferase matters
Growth-phase support follows
Stopping removes the benefit
Connect activation to variability
Follicular sulfotransferase converts minoxidil to an active sulfate metabolite that opens ATP-sensitive potassium channels. Response varies among patients.
Follow the container
A current 5 percent solution label for men directs 1 mL twice daily to the vertex scalp. Other solution and foam products have different labeled populations and schedules, so directions cannot be transferred.
Prepare for time and shedding
Results take months and may begin with a temporary increase in shedding as follicles cycle. Continued use is needed to maintain benefit; more product does not improve results.
Screen safety and technique
Apply to dry scalp skin, wash hands, allow drying, avoid eye or body exposure, and review flammability. Stop and seek care for chest pain, rapid heartbeat, faintness, dizziness, unexplained weight gain, edema, or severe irritation.
Quick check
Lesson
Select Systemic and Procedural Options Deliberately
Finasteride, spironolactone, low-dose oral minoxidil, dutasteride, devices, procedures, and transplantation differ in approval, mechanism, reproductive risk, monitoring, and evidence.
- Finasteride
- Spironolactone
- Oral minoxidil
- Off-label use
- Hair transplant
Lowers scalp and serum DHT
Selected patients need potassium review
Pressure, pulse, edema, and hair growth matter
Evidence and candidacy differ
Use finasteride precisely
Finasteride 1 mg once daily is labeled for male pattern hair loss in men. It inhibits type 2 five alpha reductase, takes months, and requires continued use.
Counsel reproductive and sexual safety
People who are or may become pregnant should not handle crushed or broken finasteride tablets because of risk to a male fetus. Review sexual dysfunction, mood symptoms, breast changes, fertility concerns, and PSA interpretation.
Treat off-label therapy as off-label
Spironolactone and low-dose oral minoxidil are clinician-directed options for selected patients. Review potassium, kidney function, blood pressure, pulse, edema, hypertrichosis, pregnancy potential, and interacting therapy as appropriate.
Place procedures honestly
Low-level light devices, platelet-rich plasma, microneedling, and transplantation have different evidence, cost, burden, permanence, and candidacy. They should not replace diagnosis.
Quick check
Lesson
Trace Diffuse Shedding Back to Its Trigger
Telogen effluvium produces delayed diffuse shedding after a physiologic or emotional trigger. Anagen effluvium follows rapid matrix injury. Medication attribution requires timing and alternatives.
- Telogen effluvium
- Anagen effluvium
- Postpartum shedding
- Medication timeline
- Nutritional deficiency
Often begins months after a stressor
Chemotherapy is a classic cause
Do not stop essential therapy blindly
Regrowth still takes time
Recognize telogen timing
Fever, surgery, childbirth, major illness, rapid weight loss, nutritional stress, endocrine change, and severe psychological stress can synchronize follicles into telogen. Shedding often starts two to three months later.
Recognize anagen injury
Cytotoxic chemotherapy and other severe matrix insults can produce rapid shedding during active growth. Timing and the treatment regimen distinguish this from telogen effluvium.
Audit medications
Anticoagulants, retinoids, lithium, valproate, some endocrine therapies, and other drugs can contribute. Establish start, stop, dose, dechallenge, competing causes, and necessity before changing treatment.
Treat deficiencies, not marketing
Check iron, thyroid, protein, zinc, vitamin D, or other factors when history and examination support testing. Excess supplementation can harm and biotin can interfere with laboratory assays.
Quick check
Lesson
Treat Autoimmune Follicle Attack by Extent and Risk
Alopecia areata is a nonscarring autoimmune disorder that can involve scalp, brows, lashes, body hair, and nails. Extent, duration, age, and burden guide local or systemic therapy.
- Exclamation hairs
- Nail pitting
- Intralesional corticosteroids
- JAK inhibitors
- SALT
Nails and other body hair add evidence
Extent and age guide delivery
Severe disease has approved options
Immune modulation requires a safety system
Recognize the autoimmune pattern
Smooth patches, exclamation-point hairs, nail pitting, ophiasis, eyebrow or eyelash loss, and rapid progression can support alopecia areata. Thyroid and other autoimmune context may matter.
Treat limited disease locally
Observation can be reasonable for selected short-duration limited disease. Intralesional corticosteroids are commonly used for a few adult patches, while topical strategies may fit children or patients avoiding injections.
Know the approved systemic options
Current approved JAK inhibitors include baricitinib and deuruxolitinib for adults with severe disease, and ritlecitinib for adults and adolescents at least 12 years old with severe disease.
Build JAK safety
Screen for infection and tuberculosis, review vaccination, CBC, liver and lipid monitoring, reproductive considerations, malignancy, cardiovascular and thrombotic risk, interactions, and product-specific renal or hepatic limits.
Quick check
Lesson
Protect the Follicle Before Loss Becomes Permanent
Traction, inflammatory scarring alopecias, and tinea capitis can initially resemble common thinning but require cause-specific intervention.
- Traction alopecia
- CCCA
- Frontal fibrosing alopecia
- Tinea capitis
- Biopsy
Early change can prevent permanence
Symptoms can precede visible loss
Systemic antifungal exposure is required
Biopsy or culture may define treatment
Interrupt traction
Tight braids, locs, ponytails, extensions, adhesives, and repeated edge tension can cause early reversible loss and later scarring. Pain, bumps, and broken hairs are warning signs.
Recognize CCCA
Central centrifugal cicatricial alopecia often begins near the crown and disproportionately affects Black women. Tenderness, itch, burning, breakage, or central thinning deserves early dermatologic assessment.
Recognize frontal fibrosing alopecia
A receding frontal hairline, eyebrow loss, facial papules, perifollicular scale, itch, or pain can signal an inflammatory scarring disorder that needs treatment to stabilize progression.
Treat tinea through the follicle
Scalp scale with broken hairs, patchy alopecia, nodes, pustules, or kerion can be fungal infection. Systemic antifungal therapy is required; shampoo alone is adjunctive.
Quick check
Lesson
Measure What Changes and Support the Person
Hair treatment takes months, response is variable, and appearance burden can be substantial. Standardized follow-up and psychosocial support are part of clinical care.
- Standardized photography
- Shedding
- Adherence
- Safety monitoring
- Camouflage and support
Anchor future comparisons
Use the same site and lighting
Reproductive and systemic risk vary
Appearance-related burden is clinical
Create a reproducible baseline
Record diagnosis, distribution, density, part width, hair caliber, symptoms, shedding, treatment, styling, and standardized photographs with consistent lighting and positioning.
Use realistic timelines
Many therapies need four to twelve months to judge. Early review can confirm technique and safety without falsely declaring efficacy failure.
Monitor the exact treatment
Topical irritation, blood pressure, pulse, edema, potassium, kidney function, CBC, lipids, liver tests, infection, reproductive risk, mood, sexual effects, and PSA matter selectively, not universally.
Treat psychosocial burden
Camouflage, fibers, wigs, scalp prostheses, styling support, counseling, and peer resources can improve function while medical treatment proceeds or when regrowth is limited.
Quick check
Module test
Check the connections.
Each attempt draws 10 questions from the complete 112 question bank.
Each attempt draws a fresh set and rearranges the answer choices.
References
Current clinical foundation.
Lecture material was synthesized with the following contemporary guidance. Verify local policy and current guidance before applying clinical information.
- AAD Hair Loss Diagnosis and Treatment
- AAD Types of Hair Loss
- AAD Male Pattern Hair Loss Treatment
- AAD Alopecia Areata Diagnosis and Treatment
- DailyMed Minoxidil Topical Solution 5 Percent
- DailyMed Propecia Finasteride 1 mg
- DailyMed Olumiant Baricitinib
- DailyMed Litfulo Ritlecitinib
- DailyMed Leqselvi Deuruxolitinib