Although my user name* may seem to suggest that I am somehow sick, I don't have any real chronic health conditions. However, my grandfather had Type II diabetes beginning in his late thirties. His hair loss started around that time in his life. It may have been a coincidence, but I believe that at the very least his condition and/or medication he took exacerbated the loss he was experiencing. Prior to developing this condition, he had the thickest head of curly hair imaginable. Photos show that he lost it all very rapidly.
Many IAHRS doctors are adamant that genetics are the only truly significant cause of balding. Dr. Bernstein, whom I saw in December, completely dismissed my suggestion that my grandpa's health condition affected his baldness in any way. Nevertheless -- and even without the presence of peer-reviewed research on this subject -- I remain open to the possibility that there may be plenty of factors that cause or affect hair loss. Genetics have surely caused mine, but perhaps things would have been different hair-wise for my grandpa if he hadn't developed diabetes.
If you have diabetes, I really wish you the best in treating it. It is a terrible condition -- I know from firsthand experience as I can't forget how much my grandpa suffered in his later years.
*It's actually the name of an excellent song by the Smiths, in case you're wondering.