Summary Box: LinkedIn 3Q results let down Wall St.

GROWING PAINS: LinkedIn lost $1.6 million in the third quarter. It marked the online professional networking service’s first loss since it wowed Wall Street with its initial public offering of stock in May. LinkedIn Corp. hadn’t suffered a quarterly loss since the final three months of 2009.

WHAT HAPPENED: The company is increasing its spending as it tries to build a business that changes the way people find jobs and advance their careers. Toward that end, LinkedIn on Thursday filed plans to sell another $100 million of its stock.

IINVESTOR REACTION: LinkedIn shares shed 9 percent in Thursday’s extended trading.