My Health
Hair loss: The latest science on causes, treatment, and prevention
By James Kingsland on November 3, 2022 — Fact checked by Rita Ponce, Ph.D. |www.medicalnewstoday.com | image credit: mfacebook.com
In the past decade, biologists have disentangled many of the complexities of how hair grows and how it is lost in conditions such as pattern baldness and alopecia areata. In this Special Feature, we explore the latest discoveries and treatments, and ask experts if it is possible to prevent hair loss in the first place. It is perfectly normal for people to shed between 50 and 100 hairs from their heads every day, according to the American Academy of Dermatology Association. However, excessive hair loss that causes progressive thinning of the hair, bald patches, or even total hair loss can be very distressing. There are several possible causes of hair loss. These include: major stressors, such as a prolonged illness, job loss, or a bereavement — this kind of hair loss is known as telogen effluviumsome medications, including antidepressants, beta-blockers, levodopa, and chemotherapy drugs illnesses such as thyroid disorders, a sex hormone imbalance, or a dietary deficiency of protein, iron, zinc, or biotin, for example autoimmunity, which can cause hair to fall out in one or more small patches on the scalp, eyebrows, or eyelashes — this is known as alopecia areata tight hairstyles that strain the hair follicles, known as traumatic or traction alopeciaa combination of genetics, male hormones, and increasing age, known as pattern hair loss or androgenetic alopecia; this can affect both males and females. The biology of hair growth is complex, but in recent years scientists have made strides toward understanding how the various factors listed above cause hair loss. They hope that in time this will lead to new, more effective treatments.
Growth cycles in hair follicles A hair follicle is a tube-like skin pore that encloses the shaft and root of the hair. Most healthy adults have around 80,000–120,000Trusted Source hairs on their scalps.
Each hair follicle repeatedly undergoes a growth cycle that comprises three distinct phases: anagen, catagen, and telogen. During anagen, which lasts between 2 and 7 years, the hair within the follicle grows about 1 centimeter per month. The follicle then enters catagen, a 2-week transitional phase during which the hair detaches from the blood supply. During the final, inactive stage, or telogen, the follicle sheds the hair. It can then take up
to 4 months before the follicle starts to grow a new one. Two to 3 months after a person experiences a traumatic or stressful event they can develop telogen effluviumTrusted Source — a type of hair loss in which the follicles remain stuck in the inactive, hair-shedding stage.
How chronic stress triggers hair loss In March 2021, scientists revealed how chronic stress can keep hair follicles in this inactive state for longer.
The hair follicle is one of the few tissues in the body that can regenerate itself, thanks to special cells known as adult stem cells. Researchers at the Harvard Department of Stem Cell and Regenerative Biology in Cambridge, MA, discovered how chronic stress in mice suppresses the activity of these cells. They showed that a stress hormone called corticosterone — which is the mouse equivalent of cortisol in humans — keeps the follicle stem cells inactive. They found that in the absence of circulating corticosterone, the stem cells underwent many more rounds of regeneration during the animals’ lifetime. By contrast, high levels of the hormone, as a result of chronic stress, kept them inactive for longer and led to fewer rounds of regeneration. Rather than directly affecting the stem cells, however, corticosterone acted on a cluster of cells under the follicle, known as the dermal papilla. The researchers showed that in mice, the stress hormone prevented the dermal papilla from producing a molecular signal called Gas6, which normally activates the follicle stem cells. They reported their findings in Nature “Under both normal and stress conditions, adding Gas6 was sufficient to activate hair follicle stem cells that were in the resting phase and to promote hair growth,” says Dr. Sekyu Choi, who was the lead author of the study. “In the future, the Gas6 pathway could be exploited for its potential in activating stem cells to promote hair growth,” he adds. The researchers say they will need to conduct more studies in mice before they can explore potential treatments in humans.
TT 176 | November 8th - November 14th | 2022
