ANCHORAGE — The head of the Alaska Permanent Fund Corp. has resigned because of undisclosed health concerns.

The departure of chief executive Mike Burns was effective Monday. The fund’s chief financial officer, Valerie Mertz, was appointed by the corporation board Monday as acting executive director for 30 days, the Alaska Dispatch News reported.

Burns announced his resignation last week, citing health problems. Corporation spokeswoman Laura Achee did not specify the health concerns.

“Mike’s a private guy, and he asked us to keep it to health concerns,” Achee said. “The board is very happy with him.”

Burns became executive director in 2004. He had recently managed about 35 employees and oversaw the fund’s first direct investment in a private venture operation. The fund — the state’s oil-wealth savings account — is best known for its yearly dividend payouts to most residents just for living in the state.

In 2014, Burns was one of the state’s highest-paid employees, earning close to $344,000 a year.

The fund totaled $26 billion when Burns took over the helm. During his tenure, Burns oversaw the fund as its value climbed to $40 billion, then shrunk to $26 billion in 2009 after the economic crash. As of late last week, the fund was valued at $55 billion.

With Mertz appointed as acting executive director, the board will have time to consider selecting an interim director. The board also plans to work on a plan to find a new executive director, a process that could take several months.