Gentex Corp. (GNTX) dropped as much as 11 percent after forecasting a sales gain this quarter that was lower than analysts estimated.

Gentex fell 9.5 percent to $23 at 10:56 a.m. New York time, after reaching $22.73, the lowest intraday level since Oct. 4. The shares declined 14 percent this year through yesterday after rising 0.1 percent in 2011.

Second-quarter sales will rise about 15 percent, Chief Financial Officer Steve Dykman said in a statement today. The average estimate of eight analysts surveyed by Bloomberg was for a gain of 19 percent to $288 million from a year earlier.

The company’s second-quarter forecast “looks a little light,” Peter Nesvold, a New York-based analyst for Jefferies & Co., wrote in a report.

Gentex. based in Zeeland, Michigan, makes rear- and side- view mirrors that include camera displays. It competes against Magna International Inc. (MG), an Aurora, Ontario-based maker of similar mirrors and cameras.

The company reported first-quarter net income of $46.3 million on revenue of $290.7 million, both records. That compares to a year-ago profit of $42.3 million on revenue of $250.9 million.

To contact the reporter on this story: Mark Clothier in Southfield, Michigan at mclothier@bloomberg.net

To contact the editor responsible for this story: Jamie Butters at jbutters@bloomberg.net