Glossary of terms used on this site

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Term Main definition
5 alpha-reductase

an enzyme responsible for converting testosterone into dihydrotestosterone


General term describing hair loss. There are different types of alopecia and different causes for it.

Alopecia areata

bald spots due to inflammation of the hair roots caused by auto-immune reaction.

Anagen phase

is the active part of the hair’s growth cycle. ( see “hair cycle”) Normally 85% of the hair is in the anagen phase, which has a 2 to 6 year duration


general term describing the full range of male sexual hormones, of which the most important is testosterone. These hormones are secreted for 95% by the testicles and for 5% by the adrenal glands, and are also responsible for almost all types of male hair loss.

Androgenetic alopecia

is the genetic predisposition for hair loss. Male and/or female androgenetic alopecia, also called androgenic alopecia or hair loss. Hair loss comes with age and manifests itself as shedding on the sides and on the top of men’s skulls (masculine androgenetic alopecia) whereas in women, a general thinning of the hair mass  (feminine androgenetic alopecia),occurs predominately  on the top of the skull. Nevertheless, diffuse hair loss also occurs in male androgenetic alopecia and hair loss on the sides of the head can sometimes occur in female alopecia


substance that blocks the functioning of male hormones. Some anti-androgens are effective for hair loss treatment.


a fibrous membrane (Galéa) enveloping a muscle or a group of muscles and acts as a separating element between them.

Arrector pili muscles

small muscle between the follicle and the skin that allows the hairs to rise when an individual is cold or scared.


when the organism considers its own cells to be foreign bodies and starts eliminating them.


Partial or complete absence of hair.


progressive depigmentation of the hair resulting from melanocyte activity cessation within the hair follicle.

Catagen phase

involution phase (regression)  in the hairs’ growing cycle. The hair stops growing. The catagen phase lasts 15 to 20 days.


term that is improperly used to describe the multiplication, in a laboratory, of hairs taken from an individual. It is  more appropriate to describe it as multiplication of follicular cell implants. 
This technique is still experimental .


upper part of the scalp, also referred to as the vertex


a device that calculates the number of hairs per square centimetre. A skull will have between 100,000 and 150,000 hairs.

Dermatitis (Seborrheic)

a skin disease that manifests itself by rash and dandruff on the scalp.

Synonyms - Seborrheic

Double Follicular Unit graft; graft containing two follicular units.

Diabetes and hair loss

blood circulation deficiency due to diabetes causes insufficient irrigation of the hair follicle’s cells, the pouch housing the hair’s root. Insufficiently supplied with vital nutrients delivered by blood flow, the hairs can no longer grow, and renew themselves in a normal way.

Diffuse Alopecia

widespread hair loss due to general illness (infectious diseases, rheumatic disorders, tumours…), to a certain type of deficiency (iron deficiency or deficiencies caused by a drastic diet), medication (chemotherapy, anticoagulants…),  high fever or  major  surgical procedures.


male hormone responsible for male androgenic alopecia.

Synonyms - DHT
Donor area

is the source that supplies the grafts that will be implanted. It’s located in the occipital and temporal regions. These areas will almost always contain hair, even in men suffering from severe baldness. Extraction can be performed either by use of the strip technique or by the 0.8 to 1mm diameter punch when performing the follicular extraction technique (FUE).

Donor zone dominance

this principle explaines how grafted hairs from the donor area (mostly present even in bald men) keep their original characteristics (genes). They will continue growing after being grafted in the bald area or the area with low density

Double follicular unit

grafts containing two follicular units.

Facial Œdema

œdema is the swelling of tissue under the influence of unusual accumulation of serous liquid. It can manifest itself after 48 hours and last for 5 to 10 days. There’s no pain involved and it normally resorbs downwards  from forehead to the lower eyelids. Applying ice packs and taking corticosteroids (Medrol) drastically reduces  facial œdema.

Synonyms - Facial oedema

specific procedure of follicular extraction or FUE that extracts one or several hairs, smaller than the follicular unit.

Synonyms - Follicular Isolation Technique
Follicular extraction

graft extraction technique by means of a punch sized from 0.9 to 1mm that allows extraction of singular follicular units.

Follicular family

two follicular units that are located very close to each other.

Follicular isolation (technique)

or FIT, term proposed by doctors Paul T Rose and John Cole for indicating the extraction of the follicular unit by means of a technique they developed ; a specific form of follicular extraction or FUE

Synonyms - FIT
Follicular Unit

a group of hairs, developing naturally in the scalp of an adult male, generally 1 to 4 hairs. Each of these groups is referred to as follicular unit.

Synonyms - FU

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