Definition of High blood cholesterol levels:

Cholesterol is a fat (also called a lipid) that your body needs to work properly. Cholesterol levels that are too high can increase your chance of getting heart disease, stroke, and other problems.

The medical term for high blood cholesterol is lipid disorder, or hyperlipidemia.

Causes, incidence, and risk factors:

There are many types of cholesterol. The ones talked about most are:

• Total cholesterol - all the cholesterols combined
• High density lipoprotein (HDL) cholesterol - often called "good" cholesterol
• Low density lipoprotein (LDL) cholesterol - often called "bad" cholesterol

For most people, abnormal cholesterol levels are the result of an unhealthy lifestyle -- most commonly, eating a diet that is high in fat. Other lifestyle factors are:

• Being overweight
• Heavy alcohol use
• Lack of exercise and leading an inactive lifestyle

Diabetes and an underactive thyroid gland may lead to high cholesterol levels. Other illnesses that may raise cholesterol levels include polycystic ovary syndrome and kidney disease.

Higher levels of female hormones increase or change cholesterol levels. This may include women who take birth control pills or estrogen, or who are pregnant,

Medicines such as certain diuretics (water pills), beta-blockers, and some medicines used to treat depression may also raise cholesterol levels.

Several disorders that are passed down through families lead to abnormal cholesterol and triglyceride levels. They include:

• Familial combined hyperlipidemia
• Familial dysbetalipoproteinemia
• Familial hypercholesterolemia
• Familial hypertriglyceridemia

Smoking does not cause higher cholesterol levels, but it can reduce your HDL ("good") cholesterol.