Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Neutral Tandem (Nasdaq: TNDM) were stuck in reverse today as they slipped as much as 19% in intraday trading after a disappointing fourth-quarter earnings report.

So what: When does growth not get investors excited? When that growth doesn't lead to more profit. For the fourth quarter, Neutral Tandem's revenue -- boosted in large part by the acquisition of Tinet -- leapt 43% from the prior year. Billed minutes jumped 25% to 29.9 billion. However, earnings per share for the quarter clocked in at $0.18, down from $0.31 last year and well short of the $0.29 that Wall Street was looking for. Adjusted EBITDA -- which allows the company to add back healthy amounts of share-based compensation -- was up slightly, but the adjusted EBITDA margin plummeted from 50% to 36%.

Now what: To truly bum out investors, it also takes a lower-than-expected forecast, and Neutral Tandem provided that as well. For 2011, management gave guidance for adjusted EBITDA of $91 million to $95 million. According to Capital IQ, analysts on average had projected EBITDA of nearly $99 million. To be sure, there are some bright spots for this Motley Fool Hidden Gems pick. The company reported increased cash flow for 2010, and it still sports a debt-free balance sheet. And based on 2010 earnings per share of $0.97, the stock trades at less than 15 times earnings -- not overly cheap, but not expensive either. However, it would seem that the company has some work ahead to jump-start its bottom line.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.