Hair loss of the scalp is of great concern to both men and women. It seems that eventual hair loss is almost inevitable. By the age of 70, nearly 80% of men and 40% of women will have noticeably thinning hair.
Normal hair growth
There are approximately 100,000 hairs on the scalp. Hair growth occurs in a cycle. At any one time an individual hair is growing, resting or falling out.
The three stages of the hair growth cycle are:
Anagen – growing phase.
Approximately 90-95% of hairs are in anagen phase at any given time.
Depending on your genes, this hair growth phase lasts from 3 to 10 years.
People with long anagen cycles can grow very long hair before it falls out.
Catagen – transition phase
A short transition phase between anagen and telogen
Less than 1% of hairs are in this phase at any given time.
The transition phase lasts about 3 weeks
Telogen – resting phase
5-10% of hairs are in telogen resting phase.
The resting phase lasts 2-3 months.
At the end of telogen, a new anagen phase starts, and a new growing hair pushes the old hair out of the follicle
With this process it is normal to lose up to 100 hairs per day.
Types of hair loss/alopecia
There are a large number of conditions that can cause hair loss or hair thinning. Loss of up to half of scalp hair occurs before hair loss is noticeable on casual inspection.
A careful history and examination of the scalp must be performed to determine the following:
Is the hair loss scarring or non-scarring?
In areas of scarring hair loss, there is disappearance of the hair follicle openings, and the skin is smooth and shiny.
Is the hair loss happening throughout the scalp (diffuse alopecia) or is it patchy?
Is the hair coming out at the roots or breaking off?
Some conditions like fungal infections of the scalp (tinea capitis), lupus erythematosus and traction alopecia, can produce both scarring and non-scarring hair loss.
Types of hair loss/alopecia
We will cover some hair loss disorders in more detail on their individual pages. Please follow the highlighted links.
Non-scarring hair loss
Diffuse
Androgenetic (female pattern, male pattern)
Telogen effluvium
Illness
Postpartum
Sudden weight loss
Medications
Toxins
Endocrine abnormalities
Hypothyroidism
Hyperthyroidism
PCOS
Alopecia areata
Loose anagen syndrome
Patchy
Tinea capitis (ringworm of the scalp)
Alopecia areata
Trichotillomania
Syphilis
Traumatic (traction alopecia)
Loose anagen syndrom
Scarring hair loss
Tinea capitis (fungal infection of the scalp)
Traumatic (traction alopecia)
Tumors, benign or malignant
Skin diseases, such as sarcoid or scleroderma
Lymphocytic
Central centrifugal scarring alopecia
Formerly called “hot comb alopecia” or “follicular degeneration syndrome”
Discoid lupus
Lichen planopilaris
Frontal fibrosing alopecia
Pseudopelade of Brocq
Neutrophilic
Folliculitis decalvans
Dissecting cellulitis
Mixed
Acne keloidalis
Acne necrotica
Erosive pustular dermatosis
Diagnosis of alopecia
Diagnosis of alopecia requires a detailed history and physical examination. For some forms of alopecia further work-up is required.
Both scarring and non-scarring forms of hair loss may require a skin biopsy to obtain a more accurate diagnosis.
Laboratory work-up of non-scarring alopecia includes:
Complete blood cell count
Iron studies, including iron, TIBC and ferritin
VDRL
Thyroid screening
Microscopic examination of hair
Possible fungal culture
Additional diagnostic methods may be necessary
Scalp biopsy
Antinuclear antibodies
Hormones
Heavy metal screens
Borate and thallium levels
References:
John C. Hall Sauer’s Manual of Skin Diseases, 10th ed. Phila, PA. LWW publishers
Norwood OT, Lehr B. Female androgenetic alopecia: a separate entity. Dermatol Surg 2000;26(7):679-82
Whiting, DA. Male pattern hair loss: current understanding. Int J Dermatol 1998;37:561-66
Bouhanna P. Multifactorial classification of male and female androgenetic alopecia. Dermatol Surg 2000;26(6):555-561
Ross EK et al. Update on primary cicatricial alopecias. JAAD 2005;53:1-37
Olsen EA. Central centrifugal cicatricial alopecia. Dermatologic Therapy 2008;21:268-278
Hordinksy M. Cicatricial alopecia: discoid lupus erythematosus. Dermatologic Therapy 2008;21:45-48
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Depending on your genes, this hair growth phase lasts from 3 to 10 years.
