Male Alopécia
  The most severe form of baldness occurs at about the age 30, it normally begins with a sudden hairloss around 17-18 years of age and lasts for three to four months. This condition usually affects several hundred hairs a day mostly on a hyper-seborrheic and at times oily scalp. New finer, thinner and shorter hair eventually replace those that were lost.

The different stages of this loss are explained below following Hamilton classification. (simplified by Rook)