SALT LAKE CITY — President Thomas S. Monson, the leader of the LDS Church, is in the hospital.

[Update: President Monson home after brief hospital stay]

"President Monson was not feeling well last evening and was admitted to the hospital," Eric Hawkins, a spokesman for The Church of Jesus Christ of Latter-day Saints, said Tuesday. "He has received treatment and fluids and will hopefully be released soon."

President Monson, 89, attended the morning and evening sessions of the 187th Annual General Conference on Saturday, but he remained at home for the afternoon session to conserve his energy.

He spoke at the beginning of the Sunday morning session, announcing five new temples and giving a short talk. He did not attend the closing afternoon session. A spokesman said then that he was weary but well.

Two years ago, a few weeks after the April 2015 general conference, Hawkins said President Monson was "feeling the effects of advancing age."

"He comes to the office every day, attends all First Presidency and committee meetings, leads the discussion and makes decisions," Hawkins said then. "The workload of the First Presidency is up to date. President Monson has always been private about his health, but appreciates the prayers and sustaining support of church members, as do all of the First Presidency and the Twelve."

President Monson had cut his speaking load at that April 2015 general conference, reducing his talks from four to two. Six months later, while he was giving a talk in the October 2015 general conference, President Monson appeared to be visibly weakened near the end of a 13-minute talk.

In December 2015, President Dieter F. Uchtdorf, second counselor in the First Presidency, said President Monson wasn't walking as briskly as he once did and that his short-term memory "is not what it once was."

President Monson again reduced his speaking load at conference in April 2016, cutting his two talks to four minutes each, a practice he has continued. Sunday's talk lasted just over three minutes. He pleaded with church members to devote themselves to daily scripture study.

"I implore each of us to prayerfully study and ponder the Book of Mormon each day," he said.

The LDS Church's leadership system ensures continuity when the church president is ill, incapacitated or dies.

The apostle with most seniority in office always has been chosen to succeed the church president following a president’s death.

"That system of seniority will usually bring older men to the office of president of the church," President Russell M. Nelson, now president of the Quorum of the Twelve, said during the faith's October 2014 general conference. "It provides continuity, seasoned maturity, experience and extensive preparation, as guided by the Lord."

He also said the system provides for "prophetic leadership even when the inevitable illnesses and incapacities may come with advancing age."

President Monson was called as an apostle in 1963. President Nelson, 92, is the next most senior LDS apostle. He was called in 1984.

Each member of the three-man First Presidency and the Quorum of the Twelve Apostles is called as a prophet, seer and revelator and holds the keys to lead the church.

If an LDS Church president becomes ill or can't function, his two counselors constitute a quorum of the First Presidency and carry on its day-to-day work. Major issues are considered together by the First Presidency and Quorum of the Twelve.

The church has functioned this way several times in the past, for example when the late President Spencer W. Kimball was incapacitated for much of the final years of his church presidency in the 1980s.

This system extends into other areas of church leadership as well. During the extended, health-related absences of the late President Howard W. Hunter while he was president of the Quorum of the Twelve Apostles in the early 1990s, then-Elder Boyd K. Packer acted as the head of the quorum in his stead.