Although castration is now considered barbaric, until as recently as 1950, in Kansas and 27 other States, institutionalized males who were labeled mentally retarded were often castrated - a holdover from 1920s eugenic laws. Castration was also supposedly used to control aggression. Statistics show that these unfortunate castrated Kansas inmates, like the neutered cats, lived longer than "matching" groups of male inmates who didn't get the knife and even lived longer than female inmates.
In 1942 a Dr. James B. Hamilton, a Yale anatomist, studied the castrated inmates. The story is that one day Hamilton noticed an identical twin of one of the inmates who came to visit his brother. The castrated inmate brother had a full head of hair. His twin, with the family jewels intact, was quite bald. This gave doctor Hamilton an idea. He experimented with the castrated brother by giving him testosterone. It is rumored that the poor inmate's voice got deeper, he developed acne, large muscles and a sex drive. Dr. Hamilton tells us that he became bald. His hair never grew back.
The "population" of institutionalized, castrated males provided Dr. Hamilton with a means of demonstrating the relationship between baldness and hormones. Testosterone was orally given to 104 castrated inmates; they were compared to 312 "normal" men. When given testosterone, the castrated inmates grew bald, if baldness was in their family history. There was a direct connection between the length of time that testosterone was given and the degree of baldness that occurred: the longer the treatment, the more baldness. Echoing Hippocrates Dr. Hamilton concluded "Men who failed to mature sexually did not become bald".
Dr. Hamilton established the cause of baldness. Hamilton's classification of degrees of baldness was updated in the 1970's by O'Tar Norwood, a noted hair replacement surgery innovator. The Hamilton-Norwood Scale is remains the standard in medicine.