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Hair
Loss Canada > Hair Loss Information
Hair
Loss Glossary
5 Alpha Reductase
5 Alpha Reductase is an enzyme which converts
testosterone to dihydrotestosterone (DHT) which is the hormone
that triggers Androgenetic Alopecia in individuals who are genetically susceptible.
Alopecia
Alopecia
is the medical term for hair loss or baldness in an area of the body where hair is
normally present. Usually, it refers to loss of scalp hair. Two patterns of hair loss are
female-pattern baldness (general thinning with moderate loss at the hair line and crown)
and male-pattern baldness (receding hair line with moderate to extensive loss at the
crown).
Alopecia
areata
Alopecia, also known as
patchy baldness, is a medical term for baldness; areata means that the hair loss occurs in
localized areas usually involving the scalp or the beard in men. It is equally common in
both sexes and tends to be more common in young adults and children than in older people.
The onset is usually sudden with the appearance of one or more patches of smooth, hairless
skin. The cause is unknown, although disturbances of the immune system (autoimmunity) may
be involved. It is more common in people with allergic problems.
Alopecia (Scalp)
Reduction
A procedure that involves removal of a strip of balding
upper scalp in the crown and vertex areas. The natural flexibility of the scalp is used to
stretch the surrounding hairy scalp into place. It can be repeated in certain cases.
Alopecia
totalis, Alopecia Universalis
Patients with alopecia areata
lose hair on their scalp in smooth round patches typically causing bald spots about an
inch (2cm) across. Sometimes the patches are larger, and the condition can include the
loss of all scalp hair (alopecia totalis), and even the loss of all body hair, including
eyelashes and eyebrows (alopecia universalis).
Androgenetic Alopecia
Androgenetic Alopecia
can be broken down in two parts. First, Androgenetic, consisting of ANDROGEN (Any of the
various hormones that control the appearance and development of masculine characteristics
such as testosterone). And GENETIC -- the inheritance of genes from either the mother of
the father's side of the family. Add AGE, which when coupled with genetics, represents a
time clock that will signal the hair follicle to produce an enzyme name 5 alpha reductase.
When the testosterone present in the follicle combines with the enzyme 5 (DHT). Hair
follicle receptors are sensitive to DHT and thereby start the process of male or female
pattern hair loss. Second, Alopecia meaning hair loss of which there are many types.
It is also known as male pattern baldness (MPB) in
men and the typical pattern of balding whereby the balding pattern is controlled by
hormones, represents close to 95% of all hair loss experienced by men. Although men are
more prone to hair loss, it is not uncommon for women to lose their hair. Women are most
likely to experience hair loss during periods of hormonal change: (1) puberty, (2)
menopause, (3) following a pregnancy, (4) following termination of birth control pills.
The anagen phase is the period of active hair growth where
protein synthesis and keratinization are continuously occurring, typically lasts
between about 3-5 years.
Anagen Effluvium
Generally due to internally administered medications, such as chemotherapy agents, that
poison the growing hair follicle. All of these represent only a few of the different types
of hair loss. Androgenetic alopecia represents close to 95% of all hair loss however.
Catagen
The catagen phase is the
resting phase of the hair cycle.
Dandruff
Skin constantly renews itself by shedding the outer layer of cells as new cells push up
from beneath. This shedding is normal, and most of the time it's unnoticeable. When flakes
of sloughed-off skin from the scalp become obvious or are accompanied by itchiness, it's
called dandruff. Dandruff can occur in all age groups.
If your dandruff persists despite treatment, or if you have very large flakes together
with symptoms around your nose, ears or chest, you may have seborrheic dermatitis.
Sometimes referred to as seborrhea, this greasy, scaly, itchy rash can occur on the sides
of your nose, in and between your eyebrows, behind your ears, in the center of your chest,
or around your navel or genitals as well as in the scalp. Or severe dandruff may be the
result of psoriasis of the scalp.
Contrary to popular notions, dandruff is usually a result of too much oiliness of the skin
and scalp rather than dryness. While mild dandruff may be caused by overactive oil glands,
recent evidence suggests that the more severe dandruff associated with seborrheic
dermatitis may be caused by an overabundance of Pityrosporum ovale, a yeast-like organism
found on healthy scalp in low numbers. With the increased scaling and oiliness of
seborrheic dermatitis, these yeast organisms thrive and multiply, aggravating inflammation
and scaling.
Dihydrotestosterone (DHT)
At the hair follicle,
testosterone is converted by an enzyme called 5 alpha reductase into another form of
testosterone called dihydrotestosterone or DHT, for short. DHT is the androgen hormone
that triggers hair loss in androgenetic alopecia. When hair follicles that are genetically
programmed to be receptive to DHT receive the DHT message over a long enough period of
time, the follicle begins to produce less hair.
Follicle
A tube-like opening in the epidermis where the hair shaft
develops and into which the sebaceous glands open.
Hair
Hair is mostly
composed of protein (97%) and water. Hair growth takes place within the hair follicle
located under the scalp. A hair shaft, the visible part of the hair, emerges from the hair
follicle.
Hair Growth Cycle
The growth of hair on the scalp follows a
repeating, three-phase cycle. The growing phase of hair lasts the longest, anywhere from
two to five years. The longer it lasts, the longer the hair. At any one time, about 87% of
the hairs on your scalp are in this phase. The second phase is a short transition period
lasting around two weeks when the root shortens and shrinks. Only around 1% of hair
follicles are in this stage at any one time. The resting phase ends hair growth. It lasts
about three months and involves about 12% of hair. On average, hair grows about 0.35
millimeters a day. Since hairs on the scalp are at different stages of the growth cycle at
any one time, it is normal to lose hair every day. In fact, we typically shed about 100
hairs a day as the cycle takes its course. With age, the rate of new hair growth gradually
slows down, resulting in thinner hair.
Medulla
The medulla is a central zone of cells present only in large
thick hairs.
Seborrheic
Dermatitis
Greasy-appearing, scaly, itchy areas at the sides of the
nose, between the eyebrows, behind the ears, or over the breastbone. Dandruff is
mild seborrheic dermatitis of the scalp.
The affected skin is usually red and greasy. On top of that there is a white or yellowish
scale that often flakes off. The most common sites are the scalp, in and between the
eyebrows, along the sides of the nose, behind the ears, the external ear canal, over the
breastbone, in the groin area, and sometimes in the armpits. It is usually asymptomatic
(causes no symptoms) but may cause itching and occasional soreness, especially in the
groin area.
Telogen
Effluvium
Usually temporary hair loss.
Causes: Physical stress -- emotional stress -- thyroid abnormalities- medications and
hormonal causes normally associated with females.
Terminal
hair
Large, heavy pigmented hairs
with a central medulla.
Traction Alopecia
Hair loss caused by physical stress and tension on the hair
such as prolonged use of hair weaving, corn rows etc. Done too tightly on weak hair these
can cause permanent hair loss.
Vellous
hair
Vellous hair is very short,
fine light colored hairs.
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