LinkedIn’s user base skyrockets. Profits, not so much.

Updated. LinkedIn (s LNKD) on Thursday announced the financial results from its first three months operating as a public company. Overall the company showed impressive user growth — but that has not started to translate into significantly higher profits.

The Mountain View, Calif.-based company, which runs the world’s largest professional online social networking site, grew to 115.8 million members by the end of the second quarter, an increase of 61 percent from a year ago. And unique visitors grew to 81.8 million per month, a year-over-year increase of 83 percent.

But the company’s bottom line did not follow its audience growth upward. LinkedIn’s net income for the quarter was $4.5 million, a relatively small increase from the $4.3 million it brought in during the second quarter of last year. Top-line revenue, however, did see a significant boost: Net revenue for Q2 2011 was $121 million, more than doubling the $54.9 million in revenue it posted during Q2 2010. In addition, LinkedIn’s Q2 income on a non-GAAP basis, which excludes certain tax charges, was $10.8 million, compared to $6.4 million for the second quarter of 2010.

Overall, it seems that the company is quickly spending its money as soon as it comes in to reinvest in further growth. “We will continue to take a long-term perspective and invest aggressively in the global LinkedIn platform,” LinkedIn CFO Steve Sordello said in a statement accompanying the earnings release.

Update: In an interview with Fortune published Thursday afternoon, LinkedIn CEO Jeff Weiner confirmed that the company is intentionally sacrificing its bottom line profits in the pursuit of faster growth:

Fortune: Earlier in the year, you forecast a potential future loss as you invested in the business. I noticed revised q3 estimates suggest you intend to turn a profit. Has there been any change to your strategy?

Weiner: No. We’re still focused on investing in the platform so we can realize the full potential of LinkedIn. That takes three forms. One is a continuation of investment in our products and creating more value for our members. The second is continuing to scale our technology platform on a global basis. And third is continuing to expand internationally. Well over half our membership now comes from overseas. We’re going to continue to invest in localizing LinkedIn in multiple languages and building out our international footprint in terms of sales offices.