ANDROGENIC ALOPECIA
Androgenetic alopecia is an inherited disease associated with sexual development. According to the ancient Greek doctors, male pattern baldness can occur in men at any age after puberty. They found that, regardless of family genetic history, young boys who were castrated before puberty did not develop androgenetic alopecia. Whereas, boys who got castrated during or after puberty have a tendency to develop androgenetic alopecia. The reason for their speculation is castration before puberty prevents hair follicles from being exposed to androgens. Castration after puberty does not avoid androgenetic alopecia. This is due to the fact that the hair follicles have been exposed to androgens. Once the follicles are androgen sensitive, androgenetic alopecia can develop.
One may associate androgenetic alopecia with “male pattern baldness”. It is the most common type of hair loss in women. Hair loss begins when the scalp hair follicles gradually reduce to smaller size, and less time is spent in the anagen active growth phase. Instead, more hair follicles concentrate in the telogen resting stage of the hair cycle. In men, androgenetic alopecia results in hair loss that is mainly involves with the top of the head and can associate with thinning and receding hairlines.
The diagram below illustrates Norwood Male Pattern Baldness. This is the standard classification of the most common types of male pattern baldness.
Type I. Minimal or no recession of the hair line.
Type II. Triangular, usually symmetrical, areas of recession at the frontotemporal hair line.
Type III. This represents the minimal extent of hair loss sufficient to be considered as baldness according to Norwood. Most type III scalps have deep symmetrical recession at the temples that are bare or only sparsely covered by hair.
Type III vertex. In this presentation, the hair loss is primarily from the vertex with limited recession of the frontotemporal hair line that does not exceed the degree of recession seen in type III.
Type IV. The frontotemporal recession is more severe than in type III. There is sparse hair or no hair on the vertex. The two areas of hair loss are seperated by a band of moderately dense hair that extends across the top. This band connects with the fully haired fringe on the sides of the scalp.
Type IV is distinguished from type III vertex in which the loss is primarily from the vertex.
Type V. The vertex hair loss region is still seperated from the frontotemporal region but it is less distinct. The band of hair across the crown is narrower and sparser. The vertex and frontotemporal regions of hair loss are bigger. Viewed from above, types V, VI, and VII are all characterized by suviving hair on the sides and back of the scalp forming a distinct horseshoe shape.
Type VI. The bridge of hair that crossed the crown is now gone with only sprase hair remaining. The fronttemporal and vertex regions are now joined together and the extent of hair loss is greater.
Type VII. The most severe form of hair loss presents as extensive loss. A narrow band of of hair in a horseshoe shaps survives on the sides and back of the scalp. This hair is usually not dense and may be quite fine. The hair is alos sparse on the nape of the neck and in a semi circle over both ears.
Norwood-Hamilton Scale of Male Pattern Baldness
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