From infancy to old age, everyone loses hair every day as hair follicles go through their normal cyclic activity of anagen (growth phase), catagen (shedding phase) and telogen (resting phase).
A full anagen-catagen-telogen cycle can take years to complete. Each follicle goes through the complete cycle 10 to 20 times over a normal human lifetime. At any given time, about 1% or fewer of scalp follicles are in shedding phase, which takes place when a new telogen (growth) phase begins. The average number of scalp hairs lost every day from a “full head of hair” due to normal catagen activity is variable, ranging up to 100 or more. Substantially more than 100 hairs lost per day is unusual and may indicate an abnormal shift in cycling activity. Each follicle is an independent unit, not acting in coordination with neighboring follicles but responding to the same growth control signals as neighboring follicles.
Hair loss due to normal anagen-catagen-telogen cycling activity is usually recognized as normal by the individual man or woman; it is the amount of lost hair he or she is accustomed to seeing. Over the course of several cycles, this normal hair loss is recognized as temporary, the lost hair replaced by new growth from follicles that shift from telogen (resting) into anagen (growth) phase.
If an unusually large number of lost hairs begin to appear in the course of grooming, or on one’s pillow or clothing, the “temporary” nature of the hair loss may be questionable. The person may begin to ask: “Am I beginning to lose hair permanently. Am I going bald?”
The question may be especially stressful for men who have close male relatives with hair loss. Androgenetic alopecia (called male pattern baldness when it occurs in men) has a genetic basis-that is, it “runs in the family”.
A man who knows he has a family history of androgenetic alopecia may worry about the daily loss of more hair than he is accustomed to observing. While a man who has a family history of male-pattern hair loss is at higher risk for androgenetic alopecia, a man cannot be sure that the hair loss he observes is an initial sign of male-pattern hair loss. In fact, many men do not begin to notice hair shedding until they begin to notice hair thinning on the scalp. Androgenetic alopecia is known to have a genetic basis, but the patterns of genetic inheritance have not been worked out with precision. A man may carry the gene or genes for androgenetic alopecia; it is difficult to predict whether he will experience balding. If relatively large daily loss of scalp hair continues over time, it becomes more likely that the man is developing the visible signs of male pattern baldness.
A man in this position need not wait for evidence of a substantial permanent hair loss to seek advice or begin treatment, if he so desires.
Other Causes of Temporary Hair Loss
Temporary hair loss may be due to a number of causes. If it persists for weeks or months, it may convincingly appear to be permanent. Consultation with a physician hair restoration specialist can be reassuring as to the cause and its resolution.
Transient hair loss is often associated with the development of hypothyroidism. Treatment of the underlying thyroid hormone deficiency usually returns hair follicles to the normal cycle and hair loss to its normal daily amount. Other conditions include severe anemia in women with heavy menstruation and inadequate iron intake after pregnancy; this can lead to transient hair loss that is usually corrected with medical treatment/iron supplementation.
Women may experience transient hair loss during or after pregnancy. The hormonal changes following pregnancy can cause an abnormal number of hair follicles to shift into catagen (shedding) phase. There is an arrest of the catagen phase and increased numbers of hairs in anagen during the pregnancy due to high placental estrogen levels that readjust following the pregnancy; once the placenta is delivered, with subsequent drop of high estrogen level, more hair shifts into catagen phase over months following the pregnancy. The change in hair cycle associated with pregnancy is almost always temporary; however, persistence of hair loss for months after pregnancy may indicate the presence of a hormonal imbalance that requires investigation.
Extreme physical or emotional stress and high fever can occasionally cause temporary hair loss. The hormonal or other cause of this type of hair loss is not well understood. A variety of emotional and physical stresses have been reported to be associated with the shift of an abnormally high number of follicles into shedding phase. Abnormal hair shedding and hair miniaturization-the condition known as telogen effluvium-can be caused by high or prolonger fever and trauma. The miniaturized hairs are shorter and smaller in diameter than normal scalp hair. The condition usually occurs several weeks after a traumatic event or illness with high fever. A condition known as anagen effluvium that causes almost immediate hair loss can develop after exposure to chemotherapy or chemicals that are direct hair follicle toxins.
Changes in the hair cycle caused by stress and fever are almost always temporary. Even so, the temporary hair loss can be cosmetically unacceptable to the individual who experiences it. Likewise, temporary hair loss associated with certain anti-cancer medications may be cosmetically unacceptable.