Hair loss in men is mainly caused due to androgenetic alopecia which is also known as “male pattern” or “common” baldness. It occurs due to the effects caused by male hormone dihydrotestosterone (DHT) on susceptible scalp hair follicles. What DHT does is that it causes hair loss by decreasing the growth (Angen) phase of the hair cycle, causing miniaturization (decreased size) of hair follicles which leads to finer and shorter hair day by day until they disappear completely.
Sensitivity to DHT is mostly observed in the hair follicles that are present in the front, top, and crown of the scalp. DHT doesn’t affect the rear and sides of the scalp which makes it pretty easy to identify the pattern. According to the Norwood Classification, this pattern of hair loss primarily begins at the temples and crown area of the scalp. Gradually it may lead to total baldness of the scalp leaving just a few strands of hair near the rear and side areas of the scalp.
DHT primarily forms due to the action of 5-alpha reductase on testosterone, the hormone which determines the sex characteristics in men.
DHT has a very adverse effect on hair of men since it lessens the growth phase of the hair cycle, resulting to miniaturized (shorter size) of hair follicles, and thus producing hair that are shorter and thinner in length until this hair totally disappear.
Hair loss in men is basically caused by these three interdependent factors namely genes, hormones and age.