Why are men more prone to kidney stones?

I do not know that there has been any reason discovered for why men are more prone to have kidney stones than females.  Some have suggested that diet may have something to do with this.  A high protein and high salt diet makes kidney stones more likely.  Men tend to have a greater intake of both protein and salt.  As women started following diets such as the South Beach diet or Adkins diet, the incidence of kidney stones have been increasing in women over the past 20 years.  Obviously, there could be some contribution for female and male hormones, but this has never been proven.