DALLAS (AP) _ University of Texas Health Science Center officials were excited and elated today that two of their researchers won the 1985 Nobel Prize in medicine for their work on cholesterol.

The Nobel Institute in Stockholm, Sweden, said today that Michael S. Brown and Joseph L. Goldstein had made discoveries about the metabolism of cholesterol and treatment of cholesterol-related diseases that ''revolutioniz ed our knowledge.''

''We're just thrilled. It's exciting. It's just fantastic,'' said Kay Pokladnik, administrative assistant for the department of molecular genetics at the UT center.

''I was awakened by the telephone and sort of overwhelmed by it,'' said Goldstein, reached by The Associated Press at Cambridge, Mass., where both men are attending a conference. ''It's obviously thrilling and exciting.''

''It's quite a shock,'' said Brown. ''I really can only say it's a moment of great surprise and I really haven't had time to collect my thoughts. You can imagine I'm a little overwhelmed right now.''

Brown, 44, is director of the Center for Genetic Disease. Goldstein, 45, is chairman of the Department of Molecular Genetics.

Brenda Ward, a secretary at the department, said when asked if the two men were expecting the award: ''Actually, I've been here nine years and I thought it would happen every year.''

The Nobel Institute said the pair's discoveries could lead to new treatment of cholesterol-related diseases.

The prize is one of a series of awards set up in the 1895 will of Swedish dynamite inventor Alfred Nobel and presented since 1901. A total of 59 Americans have won or shared the prize.

Officials said this year's prizes each carry a cash award of 1.8 million Swedish kronor - about $225,000 - the highest in the 84-year history of the prizes.