Still Hippocrates noticed that eunuchs do not grow bald. Later this same circumstance was noted by Aristotle. In the 1940's, James Hamilton wrote that the cause of baldness could be an excess of male sex hormones combined with a genetic predisposition.
There are three types of hair along the edge of the patch of alopecia - cone-shaped, clavate and in the form of an exclamation mark. Restoring hair is thin and unpigmented, and only later they get a normal color and texture.