Understanding Male Hair Loss: Causes, Treatments & Prevention

Male Pattern Hair Loss (MPHL) is very common. About 50% of men are affected. Male Pattern hair loss describes a progressive thinning, or miniaturization, of scalp hair.

Male Pattern hair loss is sometimes referred to as Androgenic Alopecia or Androgenetic Alopecia. The term Androgenic combines the words androgen and gene, because both androgens and a genetic predisposition are thought to play a role in MPHL. Androgens are hormones, such as testosterone. Miniaturization is a process by which hair becomes smaller and finer with each growth cycle until finally, it stops growing altogether. A progressive increase in dihydrotestosterone (DHT) is widely accepted as the cause of miniaturization. Men who are genetically susceptible to MPHL have increased levels of Type II 5 alpha-reductase, an enzyme that converts testosterone into DHT.

All people have DHT but only some will suffer from hair loss, because of a genetic predisposition for hair follicles with an overabundance of androgen receptors to which DHT attaches. Over time, DHT causes a gradual miniaturization and finally the death of these susceptible hair follicles. This action is largely inherited. Although anti-androgen drugs may slow or halt hair loss, they are really only effective at regrowing hair in the crown.

Mapping of the scalp for miniaturization. (This example shows early signs of balding in the frontal area.)

In Male Pattern hair loss, miniaturization occurs only to the hairs on the top of the scalp, since they are the only hairs that are genetically sensitive to effects of DHT. Hair on the sides and back are immune and therefore do not miniaturize, even when transplanted to the top of the scalp.

Norwood Scale

The Norwood Scale can be used to categorize typical hair loss patterns in men. Typical hair loss is divided into 7 categories and sub-categories. Note that a Norwood 1 indicates no hair loss.

The Norwood Scale illustrates a feature of Androgenetic Alopecia ("AGA") that makes hair transplantation possible: No matter how severe the hair loss, hair is never lost at the back or sides of the head. These regions are under different genetic control from the gene(s) that affect hair follicles at the front and top of the head. This “preserved” hair at the back and sides of the head is a reservoir of healthy follicles that can be harvested and transplanted to scalp areas where hair has been lost.

Degrees of hair loss range from this most severe form of AGA to the least noticeable loss of hair in the front temporal area above the eyebrows. Loss of hair in the front temporal area is usually the first place where hair is lost in male AGA; in some men the loss stops there and never progresses while in other men hair loss continues into other areas of the scalp. Progression of hair loss is rapid in some men, slower in others.

A hair restoration specialist can often predict the final appearance of hair loss based upon the rapidity of onset and progression.

Male AGA occurs in an array of patterns illustrated in the Norwood Scale. The Norwood Scale is used by physician hair restoration specialists in assessing hair loss and in planning hair loss treatment.