Male pattern baldness, also known as androgenetic alopecia, is the most common type of hair loss in men. It is estimated that over 50% of men will experience some degree of hair thinning by the age of 50.
The Norwood-Hamilton classification system is the most widely used scale for defining the stages and patterns of male pattern baldness.
What is the Norwood-Hamilton Scale?
The Norwood-Hamilton scale was first published in 1975 by Dr. O’Tar Norwood. It classifies male pattern baldness into seven stages, with each stage representing a progressively higher degree of hair loss.
The scale assigns a grade from I (minimal hair loss) to VII (extensive hair loss) based on the location and extent of thinning.
Hamilton later modified Norwood’s original scale by adding a Type A variant to describe diffuse thinning that often precedes more extensive hair loss. The scale is now commonly referred to as the Norwood-Hamilton scale.
Stages of the Norwood-Hamilton Scale
The classification has seven levels, ranging from minimal alopecia to baldness (total hair loss).
Stage 1
There is minimal hair loss at this point. The hairline may have slightly receded but there is no obvious thinning.
Stage 2
The hairline clearly begins to recede and shows an “M” shape. The temporal recession is more pronounced compared to Stage I but it can be considered balding.
Stage 3
The hairline recedes further and forms a deeper “M” shape. There is moderate thinning around the crown area but no obvious bald spot yet.
In this stage, it can either go to the 3A stage which shows the “M” shape disappearing because of the further receding hairline or it can go to vertex stage where a bald spot appears on the crown.
At this stage, it can’t still be considered balding. However, from this stage, every higher level on the scale can be considered balding
Read Also: AT WHAT AGE DOES BALDNESS START?
Stage 4
The hairline recedes to the point where it almost forms an “O” shape. A bald spot also develops on the crown which is still separated from the receding frontal hairline.
Stage 5
The hairline has receded farther back, intensifying the “O” shape. The bald spot on the crown broadens and joins the receding frontal hairline.
Stage 6
This stage depicts more extensive hair loss. The hairline recedes even farther back and bald spots occupy a wide area on the crown. Remnant strands of hair separate the receding frontal line and crown.
Stage 7
There is extensive hair loss on the crown coupled with a severely receded hairline. At this stage, only a horseshoe ring of hair remains on the sides and back of the head. It is the last stage and is considered total baldness at this point.
Using the Norwood-Hamilton Scale
The Norwood-Hamilton scale serves as a useful tool for both patients and physicians to assess the progression of male pattern baldness.
Identifying the stage can help determine the appropriate treatment options, whether it may be medications, hair transplants or other hair restoration procedures.
Being familiar with the Norwood-Hamilton scale helps patients understand the extent of their hair loss and what to expect in the future.
