Hair loss, or alopecia, is a very common presenting symptom, and more than one third of women have clinically significant hair loss during their lifetime. The effect of hair loss on patients’ emotions is often greatly underestimated by physicians. After bone marrow, hair is the second fastest growing tissue of the body. As a result, many different metabolic changes can manifest as hair loss being the first clinical sign of systemic disease.Treatment
Hair Biology The scalp contains, on average, 100,000 hairs. More than 90% of these hairs are actively
growing (anagen hairs). Anagen hairs are anchored
deeply into the subcutaneous fat and cannot be pulled out easily. Hair is constantly
cycling and regenerating on the scalp. Each hair shaft can persist on the scalp for
3 to 7 years before falling out and being replaced by a new hair. This anagen phase is followed by a 2-week phase of catagen, during
which there is programmed cell death; the trigger factor for catagen phase is unknown. After
catagen, the hair goes into telogen, a resting phase that lasts about 3 months. As compared
with anagen hair, telogen hair is located higher in the skin and can be pulled out relatively
easily. Normally, the scalp loses approximately 100 telogen hairs per day.
In addition to the ratio of anagen hair to telogen hair, the diameter of the hair
follicles determines scalp coverage. Vellus hairs have a hair-shaft diameter of less than
0.03 mm and terminal hairs have a diameter greater than 0.06 mm. The optimal
hairs for scalp-hair growth and scalp coverage are anagen and terminal hairs. Hair loss key points:
Causes of Hair Loss
Hair loss 1. Scarring (which occurs in discoid lupus, lichen
planopilaris, and folliculitis decalvans). Patients should see a dermatologist about this type of hair loss or 2. Non-scarring (see below) Androgenetic alopecia This is the most common cause of such hair loss, female-pattern hair loss. The role of male hormones like androgens in this type of non-scarring hair loss remains unclear. This condition often runs in families. Female-pattern hair
loss can develop any time after the onset of puberty. By age 70 years of age, 38% of women have female-pattern hair loss. It affects
the central portion of the scalp, sparing the frontal
hairline. Male patterns of hair loss
may be associated with hyperandrogenism, but the
majority of women with female-pattern hair loss
have normal serum androgen levels. Telogen Effluvium This is another VERY common cause of non-scarring hair loss. This results from an abrupt
shift of large numbers of anagen hairs to telogen
hairs on the scalp, with a corresponding change
in the ratio of anagen hair to telogen hair from
the normal ratio of 90:10 to 70:30. It is not unusual
for women with telogen effluvium to lose
more than 300 hairs per day. This form of alopecia
generally begins approximately 3 months after
a major illness or other stress (e.g., surgery, parturition,
rapid weight loss, nutritional deficiency,
high fever, or hemorrhage) or hormonal derangement
(e.g., thyroid dysfunction); it has also been
reported after the initiation of treatment with certain
medications. Chronic telogen effluvium refers to hair loss lasting more than 6 months. In some patients, this type of hair loss lasts for years. Associated (non exhaustive list) drugs
Anagen Effluvium This is hair loss associated
with chemotherapeutic agents that cause immediate
destruction and release of anagen hair.
If the cause of telogen effluvium is removed,
hair loss lasts for up to 6 months after removal of
the trigger. Associated (non exhaustive list) drugs
Alopecia Areata This is a less frequent cause of nonscarring hair loss. The estimated lifetime incidence
of this condition is 1.7%. 11 It is usually
manifested as round patches of alopecia that may
become multifocal and may coalesce into large
areas. This is frequently reversible, but it tends to be recurrent, and it can progress to total loss of scalp
hair (alopecia totalis) in 5% of women and total
loss of body hair (alopecia universalis) in 1% of
women. The cause is unknown, but it is thought
to be autoimmune. Other causes of nonscarring
alopecia are certain 1. Hair-care practices 2. Compulsive hair pulling (trichotillomania), 3. Severe
bacterial infections 4. Fungal infections like tinea capitis, 5. In some cross-sectional studies, iron deficiency
and reduced iron levels have been associated with
hair loss, including female-pattern hair loss and
telogen effluvium, but data are limited. Testing
|