The Science of Hair Loss
Hair is a key component of our appearance. Hair loss is distressing affecting millions of men and women of all ages and ethnicities. Hair loss impacts one’s self-image and confidence, quality of life, and well-being. Multiple factors both genetic and environmental interfere with the growth phases of hair leading to permanent hair loss. Without treatment hair loss is chronic and progressive.
Androgenetic Alopecia (AA) is the most common form of hair loss, affecting up to 80% of men and 50% of women. Thinning and hair loss are the result of the effects of the male hormone testosterone, specifically DHT (a testosterone metabolite), that affects androgen sensitive hair follicles causing thinning and eventually the death of hair follicles in a recognizable pattern.
While AA presents differently in men and women the causes are the same, interference in the hair growth cycle.
The Hair Growth Cycle
Our hair grows from the hair follicles in a cycle containing three phases:
- Anagen (Growth phase) where the hair actively grows and gets longer. The anagen phase lasts 2-8 years. On average 80-90% of hair is in this phase at any single time. People who have difficulty growing hair beyond a certain length have a shorter growth phase.
- Catagen (Dormant phase) is when the hair stops actively growing and separates from the follicle. It lasts for 2-3 weeks. On average 1-2% of hair is in this phase at any one time.
- Telogen (Resting phase) is where the hair follicle goes into resting mode for about 3 months and then falls out. Under normal circumstances shedding is followed by new growth. On average 10-20% of hair is in this phase at any one time.
Most of us shed 50-100 hairs a day. If the cycle is interrupted hair thins and falls out. Interruptions can occur at any stage, and can be caused by hormones, stress, poor diet, inflammation, chemical hair treatments, some cancer treatments and genetic susceptibility.
Pattern Hair loss and hair growth cycles
In men and women with AA, the growth phase is prematurely terminated which causes miniaturization of the hair follicles and leads to thinner and finer hair until the follicle becomes nonfunctional. Progressive miniaturization of follicles leads to decreased hair density. Normal hair is gradually replaced by miniaturized hair. The dormant phase is prolonged the hair falls out and is not replaced.
In women the characteristic pattern of diffuse thinning develops that at first becomes noticeable is a widening part. While male pattern hair loss is characterized by recession of the hair line at the temples, followed by diffuse thinning and eventually balding on the crown.
What causes AA?
Male hormones called androgens control hair growth combined with thyroid hormones and female hormones. Testosterone plays a key role in permanent hair loss. Hair follicles metabolize testosterone creating DHT which halts hair growth in hair that is sensitive to DHT. Sensitivity is determined by genetics.
It is possible to regrow hair if the hair follicle is intact. However, if the follicle shrivels up it cannot regrow hair. AA can cause permanent hair loss. So, if you are losing your hair or it is thinning, the best time to address it is now while you have options. When you have a family history of AA or thinning hair make an appointment with Dr. Zeena at New Orleans Aesthetics to discuss possible treatment options.
At a Glance
Dr. Zeena Al-Dujaili
- Double board certified in dermatology and Mohs Surgery
- Fellowship trained in cosmetic dermatology
- Authored several chapters in clinical textbooks and peer-reviewed publications
- Learn more