A 48-year-old Caucasian man, diagnosed with diabetes 5 years ago, comes to the physician because of palpitations, Physical examination shows a diffuse darkening of his skin and testicular atrophy. Laboratory studies show elevated liver function and elevated blood sugars. A liver biopsy shows significantly elevated iron levels A diagnosis of hereditary hemochromatosis is made. Which one of the following laboratory findings is seen in hereditary hemochromatosis?