Male pattern alopecia is a common condition and affects about 30 to 50% of males over the age of 50.  In pattern hair loss a bald spot may develop over the back or the top of the scalp and it generally progresses to cover the whole scalp.  In some men hair loss progresses very quickly and they are almost bald within five years and in some men the progress is very slow and happens in over 15 to 25 years.  Norwood classification is the most common method used to classify the hair loss in men.  In this type of classification the hair thinning starts near the temples and moves to cover the whole scalp. The various grades of hair fall based on Norwood Classification include:

• Stage I: Minimal recession of the hairline but no significant hair loss.
• Stage II: You will notice a slight recession in your hairline. This will happen in a triangular fashion around the temples. This stage of hairline is also called as adult or mature hairline.
• Stage III: This is the stage when you will start to notice significant balding. According to Norwood this stage is considered baldness. You will notice recession along the hairline and both temples in an M, U, or V shape.
• Stage IV: This is a more severe stage than stage III and the vertex loses most of the hair and the area is left with no sparse hair. The two areas of hair are separated by a band of lightly placed hair on the sides of the scalp.
• Stage V: The demarcation between the two areas is clearly visible and the narrow band becomes narrower and sparser.
• Stage VI: The area on the top of the scalp becomes bald and the balding areas of the temple merge with the blading area at the vertex. Hair loss also increases.
• Stage VII: Only a narrow band of hair remain on the back and sides of the scalp. The hair loss is quite voluminous and the remaining hairs are very fine and sparse.