What causes hair loss?

There are a number of reasons why men lose their hair ranging from the side effects of a drug or other medical treatment, to malnutrition. The so-called male pattern baldness is known as androgenetic alopecia and it is caused by a hormone change among men who have a particular genetic inheritance. Thus, propecia is only a treatment for baldness that presents in the classic pattern where the hairline slowly retreats to form a characteristic M shape.

Human hair usually grows about one inch every two months over a period of about four years. At the end of the period of growth, a hair rests and then falls out to be replaced by another hair from the same follicle or root. At each shedding, the replacement hair is slightly thinner than the last. Baldness occurs when the follicles shrink and no new hair is grown. Why this happens is not completely understood but, because the follicle remains healthy, there is a possibility of regrowth.

How does propecia work?

Although the reason for this particular form of hair loss is not completely understood, it seems to be associated with the excessive conversion of testosterone into dihydrotestosterone. Propecia prevents this conversion and the evidence from double-blind, randomized clinical trials consistently demonstrates that hair loss slows and stops. Some regrowth then occurs from dormant follicles. All the men in the clinical trials who were unlucky enough to draw the placebo continued their hair loss. In other words, there is no psychological contribution to hair loss.

What do the clinical trials show?

Over a two year period, there is an almost 90% success rate among caucasian men aged between 18 and 40 years. The results are slightly less impressive for the other races. This was measured both by physical counts of the hair in defined areas of the scalp and by self-assessment. But, when treatment is stopped, hair loss resumes shortly afterwards. This drug is only effective during the time you take it.