Stephen Blyth, head of the Harvard University endowment, is taking a medical leave of absence effective immediately, the investment group said Monday.
Robert Ettl, Harvard Management Co.'s chief operating officer, will serve as interim chief executive of the $37.6 billion endowment until Blyth's return. Ettl joined HMC in 2008.
Harvard University president Drew Faust addressed employees of the investment group Monday morning at their downtown Boston office, according to a person with knowledge of the meeting, who was not authorized to discuss it publicly.
Blyth's leave comes a year and a half after he was promoted to the top job at the nation's largest university endowment. He is attempting a major overhaul of the Harvard fund, which in recent years has trailed its university peers on investment performance.
A spokesman declined to elaborate on the reason for Blyth's medical leave. Wiry and energetic, Blyth is a 48-year-old quantitative math specialist from London, with an exacting style. In the past, he has worked on Wall Street and taught courses at Harvard.
The fund had a 5.8 percent return for the fiscal year ended June 30, underperforming Yale University, the Massachusetts Institute of Technology, Stanford University, and other rivals.
While Blyth is away, the fund's investment committee will be cochaired by Rene Canezin, head of fixed income, and Rich Hall, head of private equity.
Blyth so far has shifted the fund's investment asset-allocation approach and changed staff compensation to encourage cooperation and produce better performance across portfolios.
Several ranking executives have left on his watch, and this month, eight members of the public equities team were cut. Blyth has said he is open to outsourcing more assets to outside firms, if the returns are better. "We have a highly experienced executive team at HMC and, together with Bob, they will provide strong leadership in Stephen's absence," said Paul J. Finnegan, chairman of the endowment's board of directors. "We look forward to Stephen's return to the company, and wish him well as he returns to full health."