At 54, Milan Kunz seemed destined for an auspicious future in Downingtown.

Happily married, the father of five, and a leader in his church, Kunz last year left the pharmaceutical giant GlaxoSmithKline P.L.C., where he had been a senior vice president, to start a consulting business.

But a phone call has put an end for now to his business career.

In a few weeks, he will move his family to Omaha, Neb. For the next three years - and for no pay - he will supervise 142 Mormon missionaries in Nebraska and parts of Iowa and Kansas.

"It's a choice - but we would never say no," Kunz (pronounced "Koontz") said as he and his wife, Leslie, watched their two youngest sons play Ultimate Frisbee at Downingtown West High School.

Their formal calling came via a teleconference with one of the 12 apostles, or top leaders, of the Church of Jesus Christ of Latter-day Saints, as the Mormon Church is formally known. "We believe we were called by a prophet of God to serve this mission," Kunz said.

With about 14 million members worldwide, the Mormon Church is among the fastest-growing religions. Nationally, it counts about six million adherents, more than Presbyterians and Episcopalians combined.

Some of its most rapid expansion in the last decade has been in the Philadelphia area, where it has about 12,000 members. Last year, the church announced plans to build a temple in the 400 block of North Broad Street, the first in Pennsylvania, New Jersey, or Delaware.

Despite its size, the church has no paid clergy. Instead, it taps Mormon men, often in the prime of their careers, to serve as church leaders anywhere in the world.

There are about 100 missions in the United States and Canada, said Kim Farah, a church spokeswoman in Salt Lake City.

"First and foremost, the church looks for men who are spiritually qualified," she said. "Issues such as health, timing, and finances are secondary considerations."

They receive no salary but are reimbursed for living expenses. "You don't volunteer for it. They ask you," said Brent Olson, who had been an attorney for Merck & Co. Inc. for 28 years. After serving nearly 10 years as unpaid president of the Philadelphia Stake - roughly equivalent to a diocese - he got a call last month asking him to become mission president for northern Utah in July.

"We were very much settled here," the 62-year-old Olson acknowledged. But with their seven children grown, he and his wife are "excited to be doing something new."

The senior Kunzes said they were "glad" to sacrifice.

The church "has to have leaders because [it is] growing so much," Leslie said. "But it's hard to uproot your family."

The Kunzes' two older sons have already left home; their 19-year-old daughter is a sophomore at Brigham Young University.

After their game, their younger sons joined them on a bench inside the high school to talk about the move.

"I really don't care," said Matt, 13. He said he would miss his friends but figured he had time to plant roots in Omaha.

He nodded toward his 17-year-old brother. "He's the one who's got to start his senior year with 'Hi, my name's Dan. What's yours?' "

Dan, whose black T-shirt bore the logo of the Christian death-metal band Impending Doom, gave a glum smile. "Nebraska," he murmured, and shook his head. "Yeah, I'd rather not go."

He and his classmates already had plans for their last year at Downingtown West. "We were working on some senior pranks," he said. Instead, he'll be "the new kid" in a city he has never seen. "Then it's off to college. So I'll just see what happens."

For their parents, however, service is a familiar part of being Mormon. Both were missionaries for two years starting at age 19 - he in Ireland, she in Texas - and they have been active ever since.

Until recently, Milan was first counselor to the president of the Valley Forge Stake. And starting at 6 a.m. every weekday for five years, Leslie has taught scripture and church history to Mormon teenagers in her home.

As head of the Omaha mission, President Kunz will counsel the missionaries in his charge - most in their early 20s - and "help them stay focused." Leslie, who will have the title Sister Kunz, will cook dinners for the missionaries as they arrive and depart, and oversee their health care.

"It's a very committed life," she said.

Mike Murray, the Philadelphia Stake's mission president since 2007, called his two years here "the most remarkable experience of my life."

A Stanford University graduate who converted to Mormonism as a young man, Murray, 54, helped develop Apple's first Macintosh computer in the early 1980s.

He then worked for Microsoft Corp., leaving early this decade to cofound UNITUS, an international antipoverty organization that makes microloans to small businesses in places such as Bangladesh.

His moorings in Seattle were "pretty deep" when the church called him to Philadelphia, Murray acknowledged, "and it took a while to get unmoored."

But he likened mission presidency "to going through rehab."

"You're forced to reevaluate yourself," he said. "What you believe, your values, how you spend your time, your relationship with your spouse and children - they're all placed before you. You ask yourself, 'What matters most?' and 'How am I going to spend the rest of my life?' "

He and his wife, Joyce, plan to return to Seattle next year but don't know what they'll do next.

"We're asking how we can best help people live better lives," he said. "We as humans have no real knowledge of how many layers there are to the onion each of us is."

An unplanned detour into mission presidency "can be a tremendous sacrifice," he said. "But it's an even greater gift."

Contact staff writer David O'Reilly at 215-854-5723 or doreilly@phillynews.com.