Diabetes and Lipid Clinic of Alaska

 

 


Lipoprotein (a)

Lipoprotein (a) or Lp(a) for short, is a form of LDL in the blood and is related to the risk of heart disease and stroke. In 1963, Scandinavian researchers reported that men with high levels of Lp(a) were more susceptible to coronary heart disease (CAD) than men with low levels. Unfortunately, because of difficulty testing for Lp(a), these findings were ignored for more than 20 years. Then 15 years ago, American researchers began re-examining Lp(a). They have since found that a high concentration of Lp(a) in the blood is a major risk factor for atherosclerosis, or “hardening of the arteries,” the disease that causes heart attacks and most strokes. The risk is independent of age, sex, diet, physical activity, smoking activity, alcohol consumption, and even cholesterol level. High blood levels of Lp(a) may be associated with up to 25% of early heart disease (before the age of 55 in men, and 65 in women). Elevated levels of Lp(a) are also associated with significant carotid atherosclerosis, which can cause stroke, even in the absence of clinical heart disease.

It is not fully understood how Lp(a) causes or promotes atherosclerosis. There is active research going on regarding several possibilities. A major component of Lp(a) is called apo(a), which has been described as a giant mutant of another component in the blood called plasminogen. This is interesting because plasminogen plays a key role in preventing the blood from forming clots too readily. Apo(a) is able to prevent the activation of plasminogen, and therefore may promote the excessive formation of clotting, which is a major component of atherosclerosis, as well of heart attacks and strokes, In addition, Lp(a) may deposit its cholesterol load and other fatty debris in the blood vessel directly.

There is no evidence that lowering levels of Lp(a) decrease the risk of heart disease or stroke. However, people with high levels of Lp(a) can decrease their risk by lowering levels of LDL cholesterol. Therefore, a high level of Lp(a)  serves as an indication that cholesterol should be treated more aggressively. It makes sense that levels of Lp(a) should be decreased in people at risk, however, this is difficult to do. Improved diet and increased exercise do not lower Lp(a) as they do for cholesterol. Importantly, estrogen replacement in postmenopausal women can have a significantly effect in decreasing levels of Lp(a). Testosterone replacement can also decrease Lp(a) levels at it maximum dose.

The only other medication that has been shown to decrease Lp(a) is the vitamin niacin. Niacin is also used to lower cholesterol in some persons, and in someone with high levels of both cholesterol and Lp(a), niacin may be a good choice. However, niacin therapy is not currently recommended simply to lower Lp(a) and should certainly not be taken except under the care of a physician.