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We have now entered an era where hair loss or hair thinning can be treated.

We have now entered an era where hair loss or hair thinning can be treated by a treatment suitable for each person.

Why does androgenic alopecia occur? What is the mechanism behind hair loss? The mechanism behind hair loss has been elucidated and thus an avenue of treatment has been provided. Professor Satoshi Itami, a leading authority on hair science, took leadership in the development of evidence-based clinical practice guideline.

A signaling from androgens controls hair growth

Why does androgenic alopecia occur? To what extent is the mechanism behind the disease elucidated?

Androgenic alopecia was already known to be a genetically determined disorder 70 years ago. It was also known that there was a marked variation in other races and that androgens were strongly related to the disease at that time. Speaking of variation in races, Anglo- Saxons tend to develop androgenic alopecia at an early age and have rapid disease progression. On the other hand, Japanese people develop it at a later age and have slower disease progression. The incidence of the disease in the Japanese is around 30% on average in all age groups, while it is over 40% in Anglo-Saxons. However, the incidence of androgenic alopecia n South Korean and Chinese people is known to be lower by 10% than the Japanese although they are all Asians. However, it has been relatively recent that the mechanisms of causing androgenic alopecia by two factors, genetics and androgens, have been elucidated.

Could you explain its mechanisms in detail?

Testosterone is a representative of androgens. When testosterone flows through the bloodstream and enters cells, it is converted into a substance called as dihydrotestosterone (DHT) by a certain enzyme.
The DHT enters in the nucleus of dermal papilla cells by binding to androgen receptors in the cell and binds to target gene promoters, causing biological actions. This action is not exerted similarly in every hair. When DHT binds to Ars in cells, it causes beard growth while it sends signals that inhibit hair growth to the front or the top of the head. In people with androgenic alopecia, these types of signals are so strong that hair at the front or on the top of the head is losing earlier. Beard hair and head hair respond differently to signals when they come. Both hairs look like almost same when observed with a microscope. They have different response to information received in the cell nucleus at the genetic level.

Pharmacological treatment and autologous hair transplant become common practice

It is easier to take care of androgenic alopecia now that its mechanisms have been substantially elucidated, isn’t it?

The elucidation of the mechanism behind androgenic alopecia has paved the way for pharmacological treatment. All you have to do is to develop a drug designed to block a signal that inhibits hair growth.
That is why a medication called as “finasteride” has been developed. By inhibiting a reductase, finasteride prevents conversion of testosterone into DHT, resulting in a decrease in the level of inhibitory signal.
The drug was originally developed for the treatment of benign prostate hypertrophy and was later found to be effective for androgenic alopecia. The drug is now commercially available under the product name of “hair growth product” or “Propecia”. There is a clinical study result showing that after three years of treatment, 80% of men taking finasteride experienced a “slight increase of hair volume”.
There is another topical agent called as “minoxidil” (minoxidil 5% solution is commercially available under the trade name of “RiUP X5” in Japan). The drug was originally used as a vasodilator; its effect of stimulating hair growth was regarded as one of the adverse effects at that time. Minoxidil promotes hair growth by secreting cell growth factors from dermal papilla cells unlike finasteride”.
The market of hair growth product is large so I guess manufacturers will continue various approaches to develop a new product. I believe they have a great potential of developing a new drug.

In addition, there is a treatment option of increasing hair volume by hair transplantation, isn’t there?

Yes. It is a surgical technique that moves individual hair follicles from a part of the body site having a normal hair cycle to the site in which hair stops growing and entrenches it. Most common method is to involve removing healthy hair follicles from an area at the back of the head to the front or the top of the head.
When explaining the mechanism for stimulating hair growth a while ago, I told that androgen receptors play an important role. More precisely, the receptor does not necessarily exist in hair follicles in every site. Androgen receptors exist in dermal papilla cells at the front or on the top of the head, while they are not present in the back of the head. Without receptors, signals from androgens do not reach. It is also clear that there are many patients with androgenic alopecia who have sparse hair on the top of their head while still having hair on the back of their head. As autologous hair transplant causes no rejection response, a surgical procedure is relatively easy. However, the number of hairs transplanted is limited and I think it will be at most 100,000 hairs.

Making good use of evidence-based guideline

I see that patients have so many options for the treatment of androgenic alopecia such as oral pharmacologic therapy, topical therapy and follicular unit transplantation, hair growth treatment using LED light and moreover wigs compared with 20 years ago.

I think patients of the day are very lucky because they consult their doctor and can select a treatment suitable for themselves and use several treatments in combination.
For this purpose, it is important to formulate the clinical practice guideline on hair medicine effectively.
It is necessary to develop the guideline by collecting internationally-recognized research papers and then by evaluating them from a neutral perspective. The guideline should contain evidence-based recommendations to physicians. This type of evidence-based treatment is also emphasized in other medical fields as well. The Japanese Dermatological Association to which I belong published the Clinical Practice Guideline for Androgenic Alopecia for the first time in 2010. The guideline is generally revised every several years. Even though a therapeutic method has low grade of recommendation at present, the grade may become higher if evidence accumulates.

Interviewer/writer: Takaki Hiroshige Photographer: Kuninobu Akutsu

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