UPDATE 1-Tenet Healthcare to replace CEO, 'refresh' board

(Adds details on timing of changes, background)

NEW YORK, Aug 31 (Reuters) - Hospital company Tenet Healthcare Corp said on Thursday it is replacing longtime Chief Executive Trevor Fetter and plans to alter the composition of its board.

Two weeks ago, the company's largest shareholder, Glenview Capital Management, pulled two of its executives from Tenet's board, citing irreconcilable differences over strategy.

According to a person familiar with the matter, the timing of Tenet's move was in anticipation of Glenview coming out with an aggressive plan for changes, as a standstill agreement with the company was due to end on Friday.

Shares of Tenet, one of the largest U.S. hospital companies, have lost nearly three-quarters of their value since 2015. Hospital companies have struggled over that period because of fewer patients, rising expenses and high debt.

Fetter, who has led the company since 2003, will step down as CEO and as a director by March 15, 2018 or when a successor is appointed, whichever comes earlier, the company said. The company has already begun the search for a new CEO.

Tenet said independent lead director Ronald Rittenmeyer will become Tenet's executive chairman effective immediately.

It also said it has started a process to "refresh the composition" of its board, but it did not say how many directors, if any, it intends to replace. (Reporting by Michael Erman; Editing by Chris Reese and Grant McCool)