Boston Properties Inc., the biggest U.S. office real estate investment trust, reduced its forecast for 2013 funds from operations as it absorbed costs relating to the hiring of a new chief executive officer.

The REIT estimated full-year FFO of $4.97 to $5.07 a share, compared with January’s projection of $5.06 to $5.18. FFO for the first quarter was $160.6 million, or $1.06 a share, down from $166.7 million, or $1.12, a year earlier, the Boston-based company said in a statement. The average estimate of 19 analysts was $1.21 a share, according to data compiled by Bloomberg. FFO gauges a property company’s ability to generate cash.

Owen Thomas, a former chairman of Lehman Brothers Holdings Inc., replaced Mortimer Zuckerman as CEO on April 2. Zuckerman remains executive chairman. Thomas had overseen the sale of assets, including apartment operator Archstone Inc., to repay creditors after Lehman filed for bankruptcy in 2008.

Boston Properties owns or has stakes in Boston’s John Hancock Tower, Manhattan’s General Motors Building and other office properties in New York, Boston, Washington, San Francisco and the Princeton area in New Jersey.