People younger than 60 who have high blood pressure should be tested for abnormal levels of certain blood fats before taking medication, which could increase their risk of heart attack, a University of Utah researcher reported Friday.

Millions of Americans may have high blood pressure, or hypertension, accompanied by abnormal blood-fat levels that go undetected and untreated, said Dr. Roger R. Williams of the University of Utah.Yet the abnormal blood-fat levels are probably more dangerous than the hypertension, and are made worse by two commonly prescribed hypertension medications - diuretics and beta blockers, Williams said in a telephone interview.

People under 60 who have high blood pressure have a one-in-seven chance of also having abnormal levels of three particular blood fats, said Williams, director of the university's Cardiovascular Genetics Research Clinic.

The three are high-density lipoprotein cholesterol or "good" cholesterol; triglycerides; and low-density lipoprotein cholesterol or "bad" cholesterol, Williams said.

Williams and fellow researchers found high levels of bad cholesterol and triglycerides and low levels of good cholesterol in many of subjects they studied while they were looking for inherited factors in high blood pressure.

The team reported its findings in Friday's Journal of the American Medical Association.

Chosen for the study were sets of siblings diagnosed with high blood pressure. They all had received treatment before the age of 60.

Of a total of 131 subjects, 69 had abnormalities in cholesterol and triglyceride levels in addition to their high blood pressure, but only three of those 69 were getting treated for the blood-fat abnormalities, Williams said.

High blood pressure, which afflicts about one in five U.S. adults, is a leading cause of heart attack and stroke.

But Williams said the study showed doctors were failing to treat patients' underlying blood-fat problems even though "the level of abnormality of lipids puts them at much greater risk of heart attack than high blood pressure."

"Unfortunately, that's not surprising," said Dr. R.W. Wissler, a cardiovascular pathologist and professor at the University of Chicago who was asked to comment on the study.

"It's only been a few years since doctors learned about any relationship between anti-hypertensives and the lipids, and it is just now being reported in more detail," he said. "Things sometimes build up slowly in medicine, which makes it all the more important that this be given more attention."

The blood fats in question are the components of total blood cholesterol. Cholesterol is a natural substance manufactured by the body and necessary for building cells, making hormones and helping digestion. But in excess, it is a contributor to fatty build-up in blood vessels that can lead to heart attacks.

Diuretics and beta blockers can throw the blood-fat levels further out of proportion, so patients will a blood fat problem may need more aggressive treatment for it than for their high blood pressure, Williams said.

Such patients may have have an inherited condition Williams calls familial dyslipidemic hypertension, also associated with being moderately overweight, he said. The condition appears to afflict 1 percent to 2 percent of the population, he said.