NEW YORK — McDonald’s says its chief operating officer is retiring and that it won’t fill the position.

The world’s biggest hamburger chain says Tim Fenton, 56, will retire in October, then act as a special adviser to CEO Don Thompson. Fenton joined the company as a teenager in 1973 in Utica, N.Y.

The company says Fenton will not be replaced. Instead, it’s expanding the responsibilities for Chief Financial Officer Pete Bensen and Global Chief Brand Officer Steve Easterbrook.

The change in the executive structure come as McDonald’s Corp. faces a variety of challenges around the world, such as intensifying competition and changing eating habits.