Ambassador Jeane J. Kirkpatrick, the U.S. representative to the United Nations, was discharged from New York Hospital today. Tests showed her chest pains were caused by an adverse reaction to a change in thyroid medication, her aides said.

Meanwhile, diplomats said that at Kirkpatrick's request, balloting in the Security Council for the nomination of the next secretary general has been put off one day, until Tuesday.

Kirkpatrick checked into the hospital Thursday night for a "check and rest" after complaining to aides of mild chest pains during a flight from Washington to New York. She left this afternoon, according to a hospital spokesman.

Earlier tests showed the 54-year-old ambassador had not suffered a heart attack, according to a spokesman for the U.S. Mission to the United Nations.

A statement given to a hospital spokesman by the U.S. Mission press office said Kirkpatrick had suffered no heart damage and "the problem is not expected to recur."

The hospital spokesman did not know why Kirkpatrick was taking thyroid medication.

Kirkpatrick is expected to be fit enough to take her place in the Security Council when it meets behind closed doors to resume the election process. The council had planned to meet Monday.

Kurt Waldheim of Austria, the incumbent, and Salim Ahmed Salim of Tanzania, the only official candidates, have both been vetoed during three days of balloting, which was suspended on Nov. 4.

Diplomats said today there was very little prospect of an early solution to the problem but council members felt they must expedite their efforts as the General Assembly, which makes the appointment, has only a month left of its current session.