MADRID, Feb 5 (Reuters) - Spanish pharmaceutical company Grifols hired a new chief executive and two founding family members will leave executive jobs, it said on Monday, four weeks after short-seller fund Gotham City questioned its accounting, triggering a share slump.

Nacho Abia, a former top executive at Tokyo-based medical firm Olympus, will be appointed to the board on Feb. 26. and take over as CEO on April 1, Grifols said in a statement, adding the management restructuring process had started two years ago.

Thomas Glanzmann, who is CEO and executive chairman, will keep his chairman role.

Raimon and Victor Grifols, respectively Chief Corporate Officer and Chief Operating Officer, will voluntarily leave their jobs, though both will remain board members.

"The moves are part of a long-planned, carefully architected corporate governance evolution strategy that Raimon Grifols and Víctor Grifols Deu initiated in 2022," the statement said, implying the decision was unrelated to the Gotham City report.

The corporate governance changes intend to set "a new standard for family businesses listed on the Spanish Stock Exchange," the company said.

Since Gotham City issued its report on Jan. 9, suggesting accounting irregularities at Grifols, the company's shares have lost more than a quarter of their value, or about 2 billion euros ($2.15 billion).

Grifols has filed a lawsuit against Gotham City and its founder Daniel Yu seeking damages.

($1 = 0.9314 euros) (Reporting by Inti Landauro and Corina Rodriguez; editing by Barbara Lewis)