Founder of PacifiCare to Retire as Chairman : Management: Samuel J. Tibbitts’ successors are two executives who have guided the Cypress firm’s recent strong growth.

Samuel J. Tibbitts, founder of PacifiCare Health Systems Inc., announced Thursday that he is retiring as chairman of Orange County’s largest health maintenance organization.

Tibbitts, who will remain with the company as chairman emeritus and vice chairman, will turn over the reins to a pair of executives who have guided the company’s recent strong growth. Terry Hartshorn, chief executive officer and president, will succeed him as chairman. Hartshorn’s post will be filled by Chief Operating Officer Alan Hoops.

The changes will be effective April 1, the company said.

One analyst said the shifting of duties will give the Cypress-based company greater growth-related focus. PacifiCare has been expanding its program for Medicare patients and has millions of dollars in a war chest for future acquisitions. The emphasis on growth has been largely the work of Hartshorn.

“He’s been the main guy,” said Kimberly A. Purvis, an analyst with Donaldson, Lufkin & Jenrette in New York. “He has been the major driver of the company’s strategy.”

She noted, too, that Hartshorn and Hoops have worked effectively together for years, making changes that have given the company stellar earnings in recent quarters.

“I view this as a tremendous change,” Purvis said. “Terry and Alan have worked very, very tightly together. They are a strong team.”

The announcement of management changes failed to boost the company’s stock, which has been faltering, as has stock of other managed-care providers, on uncertainty over what effect the Clinton Administration’s health care proposals might have on health maintenance organizations.

PacifiCare stock closed at $53 a share, down $1.75, in Thursday’s trading on the NASDAQ market.