1. Influence of DHT (dihydrotestosterone)

AGA is mainly caused by DHT (dihydrotestosterone ), a type of male hormone that affects hair follicles. DHT is a hormone formed when testosterone is converted by 5-alpha reductase enzyme, which adversely affects hair follicles.

• DHT Action: DHT acts strongly on certain areas of the scalp, especially the frontal (hairline) and parietal hair follicles, causing them to atrophy. As a result, the hair cycle is shortened and hair becomes thin and short and falls out.
• Reason for the M-shape: The effects of DHT are particularly strong in the temple area of the forehead.Because the hair follicles in this area are sensitive to DHT, hair recedes first from both ends of the hairline (temple area), resulting in the center portion remaining, forming an M-shaped pattern.

2. Genetic factors

AGA is considered to be susceptible to DHT due to genetic factors. In particular, genetics often determines whether a person has hair follicles that are highly susceptible to DHT.

• Genetic Influence: AGA is more likely to occur if there is someone in the family with thinning hair. If a father or grandfather had AGA, certain genes are affected and their offspring are similarly sensitive to DHT, and hair loss often begins in the temple area.
• Individual differences: Due to genetic factors, there are individual differences in the degree to which the temple and parietal areas are susceptible to DHT, resulting in different patterns of M-shaped progression.

DHT sensitivity of the scalp

Some areas are more susceptible to DHT than others.

• Frontal and temple areas: Hair follicles in these areas are very sensitive to DHT. Therefore, the forehead hair begins to recede from the temples, forming M-shaped thinning hair.
• Occipital and temporal areas: On the other hand, hair follicles in the occipital and temporal areas are less susceptible to DHT, and hair in these areas is usually less prone to thinning. Therefore, even when AGA progresses, these areas tend to remain and hair density is relatively maintained.

4. pattern of progression

M-shaped thinning hair is one of the typical AGA progression patterns, and the degree of M-shaped thinning varies according to the degree of progression.

• Early stage: The hair at the temples gradually recedes, and the hairline of the forehead gradually begins to look like the letter M. In this stage, the extent of thinning hair is limited. At this stage, the extent of thinning hair is limited.
• Progressive stage: The temple area recedes further, and the M-shape becomes more pronounced. At this stage, the center of the hairline is still relatively intact, but the hair begins to thin overall.
• Severe stage: In more advanced stages, the M-shape becomes more pronounced and eventually the entire hairline recedes, with thinning hair toward the crown of the head.

5. treatment and countermeasures for M-shaped hair loss

Like other AGAs, M-shaped thinning hair can be slowed or improved with appropriate treatment.

• Finasteride or Dutasteride: These oral medications inhibit DHT production and support hair growth; they can slow the progression of the M-shape; they can be used to treat hair loss; they can be used to treat hair loss; they can be used to treat hair loss; and they can be used to treat hair loss.
• Minoxidil: Minoxidil promotes hair growth by stimulating blood flow and activating hair follicles. Used as a topical or oral medication, it is also effective for M-shaped hair loss.
• Hair transplantation: If the M-shape has progressed too far, hair transplant surgery is an option. By transplanting DHT-resistant hair from the back or side of the head, M-shaped thinning hair can be improved.

Summary

The main cause of M-shaped thinning hair is that DHT (dihydrotestosterone) has a strong effect on the hair follicles in the frontal and temple areas, and hair loss begins in those areas. Genetic factors and hormonal influences are strongly involved, and as the disease progresses, the M-shaped form becomes more pronounced. Appropriate treatment can reduce the progression and improve hair loss.

記事の監修者

---

岡 博史 先生

CAPラボディレクター

慶應義塾大学 医学部 卒業

医学博士

医師