Reference
Glossary
Every clinical and scientific term used across Haircure, defined plainly. Click any term to copy a link, or follow “Read more” to the article that goes deeper.
#
- 5-alpha reductasealso: 5α-reductase, 5-AR, 5AR
- The enzyme that converts testosterone into dihydrotestosterone (DHT). Two isoforms exist: type 1 (mostly skin and liver) and type 2 (mostly prostate and scalp). Finasteride blocks type 2; dutasteride blocks both. Read more →
A
- Alopecia areataalso: AA
- An autoimmune condition where T-cells attack hair follicles, causing patchy or total hair loss. Distinct from androgenetic alopecia. JAK inhibitors are the first FDA-approved systemic treatment. Read more →
- Anagenalso: anagen phase
- The active growth phase of a hair follicle. Lasts 2–6 years for scalp hair. Most follicles are in anagen at any time. Treatments work largely by extending or restoring anagen.
- Androgen receptoralso: AR, androgen receptors
- The protein DHT binds to inside follicle cells. Receptor activation triggers gene-expression changes that lead to follicle miniaturisation in genetically susceptible scalps. AR gene polymorphism is the strongest single genetic marker for pattern hair loss. Read more →
- Androgenetic alopeciaalso: AGA, male pattern hair loss, female pattern hair loss, pattern baldness
- The most common form of hair loss. Caused by genetic sensitivity to DHT leading to progressive follicle miniaturisation. Affects about 50% of men by age 50 and 40% of women by age 50.
B
- Bimatoprost
- A prostaglandin analogue originally developed for glaucoma. FDA-approved as Latisse for eyelash growth. Scalp trials have been mixed but the receptor-extension mechanism is biologically real. Read more →
C
- Catagen
- The brief regression phase between anagen and telogen, lasting about 2–3 weeks. The follicle stops producing hair shaft and begins to involute. Roughly 1% of scalp hair is in catagen at any time.
- Clascoteronealso: Breezula, Winlevi, cortexolone 17α-propionate
- A topical androgen receptor antagonist. Already FDA-approved as Winlevi for acne. Phase 3 trials show modest hair density improvement for androgenetic alopecia without measurable systemic androgen suppression. Read more →
- CRISPRalso: CRISPR-Cas9, gene editing
- A genome editing system using guide RNA + Cas9 nuclease to make precise DNA cuts. The first hair-loss CRISPR trial (Phase 1, South Korea) edits the androgen receptor gene ex vivo in follicle cells before reimplantation. Read more →
D
- Dermal papillaalso: dermal papilla cells, DP cells
- The cluster of specialised mesenchymal cells at the base of each hair follicle. They instruct follicle growth via paracrine signalling. Loss of dermal papilla inductive capacity is central to androgenetic alopecia. Read more →
- DHTalso: dihydrotestosterone
- A potent androgen produced from testosterone by 5-alpha reductase. The primary driver of follicle miniaturisation in androgenetic alopecia. DHT binds the androgen receptor more avidly than testosterone itself.
- Dutasteride
- An oral 5-alpha reductase inhibitor that blocks both type 1 and type 2 isoforms. Reduces serum DHT by 90%+. Approved for benign prostatic hyperplasia; used off-label for androgenetic alopecia at 0.5mg daily. Read more →
E
- Exosomesalso: exosome, exosome therapy
- Small extracellular vesicles secreted by cells (including stem cells) carrying proteins, RNA, and signalling molecules. Stem-cell-derived exosomes are an emerging hair-loss treatment that may stimulate follicles without transferring whole cells. Read more →
F
- Finasteridealso: Propecia, Proscar
- An oral 5-alpha reductase type 2 inhibitor. FDA-approved for androgenetic alopecia at 1mg daily. Stabilises hair loss in 80–90% of male users; visible regrowth in 65%. Known sexual side effects in roughly 1 in 27 users. Read more →
- FUEalso: follicular unit extraction
- A hair transplant technique extracting individual follicular units (1–4 hairs each) with small punches, leaving tiny dot scars. The modern alternative to strip-extraction FUT. Read more →
- FUTalso: follicular unit transplantation, strip extraction
- A hair transplant technique excising a strip of donor scalp (10–25cm long), which is then dissected into follicular units under microscope. Leaves a linear scar but allows higher graft yields per session than FUE. Read more →
H
- Hair follicle
- The skin organ that produces a single hair shaft. Each follicle cycles through anagen (growth), catagen (regression), and telogen (rest) repeatedly throughout life. Humans are born with ~100,000 scalp follicles.
I
- iPSCalso: induced pluripotent stem cell, induced pluripotent stem cells
- Adult cells (typically skin or blood) reprogrammed to a pluripotent stem-cell state, capable of differentiating into any cell type. The starting material for cell-based hair-loss therapies aiming to regenerate new follicles. Read more →
J
- JAK inhibitoralso: JAK inhibitors, Janus kinase inhibitor
- A class of drugs blocking Janus kinase enzymes in immune signalling. FDA-approved JAK inhibitors for alopecia areata include baricitinib and ritlecitinib. Investigational for androgenetic alopecia. Read more →
L
- Ludwig scale
- A three-stage clinical classification of female pattern hair loss, focusing on diffuse central scalp thinning with preserved frontal hairline. Developed by Erich Ludwig in 1977. Read more →
M
- Minoxidilalso: Rogaine, topical minoxidil, oral minoxidil
- A potassium-channel opener originally a blood-pressure drug. FDA-approved topically for androgenetic alopecia. Low-dose oral minoxidil (1.25–5mg) is increasingly used off-label with stronger efficacy and convenience. Read more →
N
- Norwood scalealso: Hamilton-Norwood scale, Norwood-Hamilton scale
- The standard 7-stage classification of male pattern hair loss, from minimal frontal recession (Norwood 2) to bilateral connection of frontal and vertex baldness (Norwood 7). Originally Hamilton 1951, modified by Norwood 1975. Read more →
P
- PRPalso: platelet-rich plasma
- Plasma fraction with concentrated platelets, prepared by centrifuging the patient's own blood. Injected into scalp to deliver growth factors to follicles. Comparable efficacy to topical minoxidil in 2025 meta-analysis, but requires ongoing maintenance sessions. Read more →
R
- Ritlecitinibalso: Litfulo
- A JAK3 and TEC kinase inhibitor approved by the FDA in 2023 for severe alopecia areata. First FDA-approved oral treatment for the condition. Investigator-initiated studies are exploring use in androgenetic alopecia. Read more →
S
- SALT scorealso: Severity of Alopecia Tool
- A clinical scoring system (0–100) quantifying scalp hair loss in alopecia areata, where 0 = no hair loss and 100 = total scalp baldness. SALT ≤ 20 is the standard primary endpoint in alopecia areata trials.
- Scalp micropigmentationalso: SMP
- A cosmetic tattooing procedure depositing pigment at the follicle level to mimic close-cropped hair. Doesn't regrow hair but provides cosmetic transformation. Best for patients comfortable with a buzzed look. Read more →
- Sinclair scale
- A five-stage clinical classification of female pattern hair loss, with finer-grained progression measurement than Ludwig. Adopted in modern clinical trials of female-pattern treatments. Read more →
T
- Telogen
- The resting phase of the hair cycle, lasting 2–3 months. The follicle is dormant; the hair shaft eventually sheds and a new anagen phase begins. Roughly 10% of scalp hair is in telogen at any time.
- Telogen effluviumalso: TE, diffuse shedding
- A common form of diffuse hair shedding triggered by physiological stress: major illness, weight loss, surgery, childbirth, severe psychological stress, or medications. Usually self-resolves within 6–9 months. Read more →
- Trichoscopy
- Examination of the scalp and hair shafts using a handheld dermatoscope at 20–70x magnification. The standard diagnostic tool in modern hair clinics, distinguishing AGA, AA, scarring alopecias, and telogen effluvium. Read more →
V
- Verteporfin
- A photosensitising drug originally for macular degeneration. Inhibits YAP signalling. When injected at hair-transplant sites, it suppresses scar formation and may enable some follicle neogenesis. Phase 2 underway. Read more →
W
- Wnt signallingalso: Wnt pathway, Wnt/β-catenin, Wnt-beta-catenin
- A cellular signalling pathway central to hair follicle cycling. Wnt ligands prevent β-catenin degradation, allowing it to drive transcription of anagen-promoting genes. Hair follicle stem cells require Wnt activity. Read more →
Spot a term we should add? Let us know. We update this page as new treatments and concepts enter mainstream coverage.