How can male hair loss be classified according to the Norwood scale?

How can male hair loss be classified according to the Norwood and Hamilton scale?

Following is the classification of hair loss in men according to Norwood and Hamilton scale:

• Type I - Minimal to no hairline recession.
• Type II - Triangular, normally symmetrical, region of fronto-temporal hairline recession.
• Type IIA : Hairline is anterior to the coronal plane 2 cm anterior to the external auditory meatus.
• Type III -Deep, symmetrical recession at the temples which are exposed or very less covered by hair.
• Type IIIA : The hairline has receded back to a point between the limit of Type IIA and the level of the external auditory meatus.
• Type IV - Worsening front temporal recession that has minimal to no hair on the vertex.
• Type IVA : The hairline has receded beyond the external auditory meatus but has not reached the vertex.
• Type V - The hair loss seen in the front temporal and vertex areas are still separate, but they are becoming less distinct from each other.
• Type VA :The area of denudation includes the vertex. Hair loss more severe than Type VA, cannot be distinguished from Types VI or VII.
• Type VI - The frontotemporal and vertex hair loss areas which are not combined, with only thin patches of hair remaining between the two.
• Type VII - Horseshoe pattern of hair remains, wrapping around the back and sides of the scalp. The rest of the head is bald.

The rate at which men lose their hair differs. Male hair loss can start even in puberty. However some men can shed hair in their 20’s up to a Type 3 or Type 4. Some of the men do not show a detectable amount of hair loss until their 50’s, only to advance to a Type 6 or Type 7 in few years. Basically, the Norwood scale is used to evaluate the degree of hair loss in a patient. The higher the grade of hair loss, the more advanced is the hair loss.