Whitworth, who was appointed chairman on an interim basis in April 2013 and has served on the company’s board since 2011, is also taking a leave of absence from his investment company Relational Investors.

“Ralph has been a friend and close advisor to me, the H-P leadership team and every member of the board for nearly three years,” Chief Executive Meg Whitman said in a statement. “We wish Ralph and his family the very best.”

H-P (HPQ) didn’t disclose any further details of Whitworth’s health in its prepared statement. Whitworth, in a statement, said he was “disappointed” to step down from the company’s board but said shareholders could be “very confident that Meg, her team and the current board will stick to the strong practices and discipline we’ve put in place.”

Whitworth, an activist shareholder, was adding to the computer maker’s board in late 2011 in a bid to help shore up investor confidence in the company. He joined H-P’s board just a few months after Whitman–who has served on the company’s board since early 2011–was appointed president and CEO.

With the resignation of Whitworth, H-P’s board now has 11 members, including Whitman.

H-P earlier this year unveiled a plan to slash as many as 16,000 jobs in a move Whitman said will make the company “more efficient and effective.” The additional job cuts are part of Whitman’s five-year plan to turn the PC maker around and is the third upward revision to job eliminations since her strategy went into effect two years ago.