UnitedHealth CEO Stephen Hemsley realized a potential gain of more than $45 million from exercising stock options last year as the share price of the nation's largest health insurer topped $100 on the way to setting all-time highs. The 62-year-old executive exercised options to buy 850,000 shares of stock at the end of 2014 at discounts of as much as 56 percent to UnitedHealth's share price of $102.24 when he exercised the options.