This test measures the total amount of cholesterol
in the blood. It is generally done together with blood tests that
measure a person's HDL, or"good cholesterol" and LDL, or "bad cholesterol".
Since high levels of cholesterol are often associated
with cardiovascular disease, the test is done to evaluate a person's
heart disease risk. It may also be ordered to detect disorders of
the thyroid gland, kidney or other body organs.
Cholesterol is attached to fatty molecules called
lipoproteins, which are carried in the bloodstream. The two major
lipoproteins are low-density lipoproteins (LDL) and high-density
lipoproteins (HDL). HDL transports excess cholesterol to the liver
for excretion in the bile, a liver product that helps with fat absorption
and that excretes waste products. It is known as the "good" cholesterol.
LDL leaves fatty deposits on the wall of the arteries, a condition
called atherosclerosis, and is known as the "bad" cholesterol. Therefore,
the ratio of LDL to HDL is a measure used to evaluate risk for heart
disease. A low LDL:HDL ratio means lower risk, and vice-versa.
Normal values for total blood cholesterol range from
140 to 310 milligrams per deciliter (mg/dl). The best range is from
140 to 220 mg/dl.
Abnormally high levels of blood cholesterol may indicate:
biliary cirrhosis, which is scarring and blockage of the bile
familial hyperlipidemia, a condition in which high blood lipids
run in a family
low thyroid activity, called hypothyroidism
heart attack, known as myocardial infarction
nephrotic syndrome, which is a kidney disease resulting in
loss of protein in the urine
Abnormally low levels of cholesterol may indicate:
an overactive thyroid, called hyperthyroidism
inadequate absorption of nutrients from the intestines, or
pernicious anemia, which is low red blood cell count from
vitamin B12 deficiency