Suppose you took out an unsubsidized student loan to pay for college back before interest rates were so low. Now you’d like to refinance.

But your lender won’t let you.

U.S. Sen. Sherrod Brown says this happens too often. Graduates and others who attended school with private loans five or six years ago are paying them back with interest rates of 8 percent, 9 percent, 10 percent and higher. And while this assures lenders a healthy profit in today’s low-interest environment, it leaves graduates with heavy debt and an inability to do what many other borrowers do: Refinance at a lower rate.