Thomas J. Schramm, chief executive of the Jackson Memorial Foundation, which raises millions each year in charitable contributions for Miami’s largest public hospital, has resigned to “pursue other opportunities,’’ according to a statement from the organization’s chairman.

Carlos Lopez-Cantera, the foundation chairman, did not announce a successor to Schramm, who is the second chief executive to leave the organization in less than two years. Lopez-Cantera said the foundation is “grateful for his hard work.”

Schramm, who served as the foundation’s CEO for 11 months, said he leaves the foundation in good financial condition and focused on a new strategy to broaden its donor base and improve public perception damaged by past “turmoil.’’

He also said he needed a break from the high-pressure world of fundraising, a profession he has pursued with South Florida institutions such as Baptist Health and Florida Grand Opera since 1986.

Schramm said that prior to his appointment as chief executive last year, the foundation raised money “for just a few entities at Jackson, mainly Holtz Children’s Hospital.’’ But now the foundation is engaged in campaigns to benefit multiple areas of Jackson.

“We’re in the midst of developing a robust fundraising plan for Jackson South,’’ he said. “We’re ready to begin expansion of the pediatric emergency room at Jackson North.’’ Other campaigns include a renovation of the women’s hospital, Schramm said, “which really would help Jackson’s competitiveness in the market.’’

Executives at Jackson Memorial Hospital — the chief recipient of the foundation’s largesse — said the organization would continue to be a valuable partner.

Carlos Migoya, chief executive of Jackson Health System, praised Schramm’s contributions to the group in a written statement.

“We appreciate Tom Schramm’s service with the organization, where he proved to be a valued professional,” Migoya said.

Marcos Lapciuc, chairman of the Public Health Trust that oversees Jackson, noted in an email that the foundation is a separate non-profit, calling it “a valuable and dedicated partner” in Jackson’s mission.

Schramm resigned less than two years after the departure of the foundation’s immediate past president, Rolando Rodriguez.

Rodriguez stepped down in September 2011, “to pursue opportunities,” according to the foundation’s statement at the time.

Rodriguez, who earned $398,121 in 2009, according to tax filings, had become the focus of criticism from the Miami-Dade County Commission after several reports by the Office of Inspector General found that Rodriguez used corporate credit card points for personal items such as golf clubs, department store gift cards and ski rentals and lift tickets at a Colorado ski resort.

Lopez-Cantera declined to disclose how much the foundation paid Schramm in annual salary, benefits and other compensation, but said Schramm did not receive a severance package.

Lopez-Cantera said the foundation is “very stable financially,’’ despite federal tax filings that indicate the organization received about $6.7 million in revenues for the fiscal year ending Sept. 30, 2011, but spent $9.5 million during the same period.

Lopez-Cantera said some expenses are actually contributions carried over from previous years. About $6.2 million of the total expenses were direct contributions to Jackson Memorial Hospital. An additional $2.3 million was spent on employee salaries, benefits and other compensation, according to the tax filings, and another $1.4 million was spent on fundraising.

Schramm said Monday that the foundation has not lost any major donors, except possibly ones who have died, and that its greatest challenge will be one that all nonprofits share: attracting new donors and retaining the old ones.

“Their finances are pretty secure,’’ he said, adding that the foundation has an $8 million to $9 million endowment.