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You are here: Home » News & Research » Hair Loss News Center » Telogen Effluvium - Why, When, and How
Telogen Effluvium - Why, When, and How
The Hair Growth Cycle
To understand telogen effluvium, we need to have some knowledge of the hair growth cycle. Hair does not grow continuously on the human scalp. The anagen (growing) phase for terminal hair can extend 3 to 7 years and is a reflection of the size of the hair follicle. Catagen is the transitional portion of the hair growth cycle, between anagen and telogen and lasts only 1 to 2 weeks. During this time, there is a rapid involution and regression of the hair follicle. The hair follicle then enters the telogen phase, which is a relatively fixed period of time, approximately 100 days, regardless of the size of the hair follicle. There is no growth of the hair shaft during this phase. It is at the end of the telogen phase that the entire hair shaft, also often referred to as the club hair, will spontaneously shed, while a new hair shaft is forming within the hair canal. The white bulb at the end of the hair, along with the loosely attached collection of friable debris gives the shed hair its characteristic appearance.
In the scalp of the healthy, young human adult, approximately 90% of the hair will be in the anagen (growth) phase and approximately 10% will be in the telogen (dormancy) phase. Less than 1% will be in the catagen (transitional) phase. When you consider that the scalp contains 100,000 hairs, with 10,000 in the telogen (dormancy) phase... and 1% of those hairs in the telogen phase will be at the end of the 100 day long phase, you can easily understand why it is normal to shed 100 hairs per day.
What is Telogen Effluvium?
When excessive amounts of hair simultaneously switch from anagen (growth) into telogen (dormancy) and subsequently shed several months later, the phenomenon is referred to as a telogen effluvium. Rarely are more than 50% of the hairs on the head involved. Telogen effluviums can be acute or chronic. When the shedding lasts more than six months or persistently recurs, it is referred to as a chronic telogen effluvium. Chronic telogen effluviums have been reported mainly in women. No racial predilection exists. Although telogen effluvium can affect hair on all parts of the body, generally, only loss of scalp hair is symptomatic. The exact prevalence is not known and getting accurate statistics would be very difficult, but the condition is quite common. Telogen effluvium can occur at any age. It is likely that most adults have experienced an episode of telogen effluvium at some point in their lives and, unbeknownst to most people, everybody has experienced the phenomenon early in life. In fact, mothers have been more aware of telogen effluviums in newborns and babies than most doctors have ever been. It is typical for a band like area of occipital hair follicles to enter the first telogen close to the time of birth and for these hairs to shed 2 to 3 months later. In the human infant, waves of hair growth occur before establishment of the mosaic pattern, which is usually present by the end of the first postnatal year.
What causes Telogen Effluvium?
In order to cause a large number of hair follicles to simultaneously switch from the anagen (growing) phase into the telogen (resting) phase, the body has to undergo some systemic insult. A telogen effluvium is not caused by topical medications. But because there is a required time lapse of several months between the inciting cause and the excessive shedding of hair, the exact cause of the telogen effluvium is often not positively identified.
A typical and common case of telogen effluvium would be the episode of severe shedding of hair that may occur approximately 100 days after a woman has given birth. The inciting factor is probably the abrupt hormonal changes that occur at the end of pregnancy. All of the hair grows back within a year.
Other causes of telogen effluvium include illness, major physical trauma, menopause, crash diets, severe psychological stress, major surgery (especially with general anesthesia), hypo- or hyperthyroidism, anemia's, acute and severe blood loss, heavy metal poisoning, etc. Chronic illness such as malignancy, and any chronic debilitating illness, such as systemic lupus erythematosus, end-stage renal disease, or liver disease can cause telogen effluvium. Immunizations also have been reported to cause acute hair shedding. Even jet lag and job changes have been reported to cause a telogen effluvium. In the United States, oral medications may very well be the most common cause of telogen effluviums. The list of medications associated with telogen effluviums is extensive and includes retinoids, beta-blockers, anticoagulants, SSRI’s, non-steroidal anti-inflammatories, calcium channel blockers, etc. In any and all cases, the common factor is metabolic or physiologic stress several months before the start of the hair shedding.