What Causes Male Hair Loss?

Androgenic alopecia (AA) is the most common cause of baldness in both men and women. Androgens are male hormones and the androgen most associated with male pattern baldness dihydrotestosterone (DHT).  Hair follicles possessing specialized receptors for DHT are genetically programmed to regress and die when exposed to this circulating hormone.  The severity and distribution of baldness are directly related to the number of hair follicles possessing DHT receptors. The specific genetic code causing androgenic alopecia has not been fully sequenced. We do know that the genes leading to androgenic alopecia are carried on the maternal X chromosome. Consequently, men who possess only a single X chromosome are much more likely to go bald than women who require AA genes on both X chromosomes. 

Circulating testosterone is converted to the more potent DHT by Type II 5-alpha-reductase (5-AR). Finasteride and Propecia are effective in treating androgenic alopecia by blocking the function of 5-AR. Many hair loss shampoos will have labels suggesting topical 5-AR blocker activity.  The safety and efficacy of topical 5-AR blockers are unknown and not regulated by the FDA.  Minoxidil (Rogaine) is a topical medicine that has been shown to prevent androgenic alopecia although it does not interact with 5-AR activity.

In male pattern baldness, certain parts of the scalp contain hair follicles with receptors for DHT. Hairs possessing receptors for DHT will be lost in androgenic alopecia. The most common areas of hair loss are in the temples, crown, and vertex.   Even in severe cases of AA, a number of hair follicles will lack receptors for DHT.  These hairs tend to be distributed on the sides and in the back of the scalp. Hair transplant surgeons will only use grafts from regions that are genetically resistant to DHT. Because these hair follicles do not possess DHT receptors the grafts can be placed into areas of baldness. The hair grafts that survive the transplant process will continue to grow as they would in the back of the scalp.  

Although every head will display it’s own unique distribution of balding many people use the Norwood system to group male pattern hair loss into classes. This system defines hair loss in a series of stages ranging from a full head of hair in class 1 to the most severe ‘horseshoe’ balding class 7. The younger a person is when they first experience hair loss, the worse their hair loss is anticipated to become.

Kolstad Hair Restoration proudly provides San Diego and La Jolla California with hair loss treatment for men. Call (858) 859-2563 or fill out a Contact Form here to schedule an appointment!



See What Pattern of Hair Loss You Have Compared To This Common Classification of Male Hair Loss

Male pattern baldness

Classes of Male Hair Loss

Class 1:
Represents the hairline of a child or teenager without any visible signs of balding.

Class 2:
Most adult men will experience thinning in the temporal hairline. If the temporal recession is minimal many experts believe that it does not represent androgenic alopecia. Small session hair transplants of 800 – 1,200 grafts are very successful in restoring temporal hair loss.

Class 2a:
The entire anterior hairline is lost. Full session hair transplants of >2,000 grafts are typically required to restore the frontal hairline.

Class 3:
Characterized by a symmetric, deepening temporal recession with preservation of a frontal forelock. Depending on the severity of the temporal recession, hair transplant sessions of >1,5000 grafts are recommended.

Class 3 vertex:
Temporal recession combined with balding in the vertex.  Hair restoration would have been staged to treat the anterior and posterior hair loss in separate sessions.

Class 3a:
The frontal and temporal scalp have few remaining hairs.

Class 4:
The crown is losing hair fast but a band of hair across the middle scalp separates the balding in front from the balding in back.

Class 4a:
The balding has progressed beyond the midpoint of the scalp extending into the crown.  

Class 5:
Similar to class 4 but with an expanded area of balding in the crown.  

Class 5a:
Similar to class 4a but with a significant extension of balding into the crown.  

Class 6:
After the loss of the central hair tuft, a single large bald area on the front and top of the scalp remains. Patients presenting with class 6 balding are still candidates for hair transplants because of the hairs present on the sides and in the back of the head.  

Class 7:
The most severe form of male pattern baldness.  Class 7 patients are typically not good candidates for hair transplants because of the paucity of hair follicles not possessing the DHT receptor.  

Before and After

Additional San Diego Hair Transplant Information

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Hair Transplant in San Diego From A Board Certified Facial Plastic Surgeon

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