Lipids (fats), together with proteins and carbohydrates, are the main components of living cells. Cholesterol and triglycerides are lipids that are stored in the body and serve as a source of energy.Desirable levels of blood fats are:
- Total cholesterol: Below 200 mg/dL
- HDL cholesterol: Men - above 40 mg/dL; Women - above 50 mg/dL
- LDL cholesterol: Below 100 mg/dL; Below 70 mg/dL for people with diabetes or heart disease
- Triglycerides: Below 150 mg/dL
- High levels of low-density lipoprotein (LDL or “bad”) cholesterol
- Low levels of high-density lipoprotein (HDL or “good”) cholesterol
- High levels of triglycerides
When LDL cholesterol levels are high, fatty deposits (called plaques) can build up in the arteries, the blood vessels that carry blood from the heart throughout the body. Over time, plaques narrow the arteries, producing atherosclerosis (hardening of the arteries). This can cause heart disease, heart attack, peripheral artery disease (reduced blood flow in the limbs, usually the legs), or stroke. Low levels of HDL and high levels of triglycerides can also increase fat build-up in the arteries. High levels of HDL cholesterol, however, protect the heart by helping to remove the build-up of LDL from the arteries.
Endocrine causes of dyslipidemia
The most common lipid disorder is hyperlipidemia, high levels of blood fat. While many of its possible causes are not related to the endocrine system, hyperlipidemia can also be related to a hormonal disease such as diabetes, hypothyroidism (low levels of thyroid hormone), polycystic ovary syndrome (PCOS), metabolic syndrome, and Cushing syndrome. Central obesity (excess fat around the waist) or insulin resistance (a condition in which the body doesn’t use insulin properly), or both—each of which are risk factors for dyslipidemia—are often found in people with these endocrine disorders.
Diabetes is a disease in which blood glucose (sugar) levels are higher than normal. Over time, too much glucose in the blood can lead to increased plaque deposits on the insides of the blood vessel walls.
Because people with diabetes are at high risk for cardiovascular disease, keeping blood sugar levels close to normal is important to prevent this and other serious complications. Regulating blood pressure and lipid levels is especially important to manage cardiovascular disease risk. The most typical lipid pattern in diabetes consists of high triglyceride levels, low HDL levels, and small, dense LDL particles, which easily stick to artery walls. This lipid pattern is linked with central obesity and insulin resistance.
Thyroid hormone regulates metabolism—how the body uses and stores energy—and affects nearly every organ in body. It also plays a role in regulating lipids. Hypothyroidism (low thyroid hormone production) can cause many of the body’s functions to slow down.
Early diagnosis of hypothyroidism is important because people with untreated hypothyroidism have abnormal lipid levels that can lead to cardiovascular disease. These patients have high blood levels of LDL, and some have high levels of triglycerides. Hypothyroidism is treated with thyroid hormone medication. Treatment usually leads to a big improvement in dyslipidemia.
Polycystic ovary syndrome
PCOS consists of a group of symptoms and changes in hormone levels. Women with this condition often have many small painless cysts in the ovaries. Symptoms include irregular or absent menstrual periods, infertility, weight problems, acne, excess facial and body hair, and thinning head hair. Most women with PCOS have insulin resistance and many are overweight.
Dyslipidemia is common in women with PCOS. They often have increased levels of LDL cholesterol. Overweight women with PCOS may also have low levels of HDL cholesterol and high levels of triglycerides. These lipid disorders put women with PCOS at increased risk for cardiovascular disease later in life. PCOS is not curable, but it can be managed with medications and changes in diet and exercise.
The term metabolic syndrome refers to a group of metabolic risk factors, described below. People who have the metabolic syndrome are at risk to develop serious conditions like cardiovascular disease and diabetes. The exact cause of the metabolic syndrome is unknown, but genetic factors, too much body fat (especially around the waist), and lack of exercise contribute to it.
The metabolic syndromeis often definedas the presence of three or more risk factors.
- Elevated waist circumference: Men - equal to or greater than 40 inches; Women - equal to or greater than 35 inches
- Reduced HDL cholesterol: Men - less than 40 mg/dL, or currently taking medication to increase HDL; Women - less than 50 mg/dL, or currently taking medication to increase HDL
- Elevated triglycerides: Equal to or greater than 150 mg/dL, or currently taking medication to lower triglycerides
- Elevated blood pressure: Equal to or greater than 135/85 mm Hg, or currently taking medication to reduce BP
- High blood glucose: Fasting glucose equal to or greater than 100 mg/dL, or currently taking medication to lower glucose levels
The main goal of treatment is to lower the risk of cardiovascular disease and diabetes. This includes quitting smoking and reducing LDL (bad) cholesterol, blood pressure, and glucose to recommended levels. Lifestyle changes also help: losing weight, eating a healthy diet with fewer fats and cholesterol, and increasing physical activity (at least 30 minutes of moderate intensity exercise most days of the week).
Many people with endogenous Cushing syndrome have hyperlipidemia due to long-term exposure to high levels of cortisol. One reason for this lipid disorder is that cortisol affects where fat is stored, and when cortisol levels remain high, fat accumulates around the waist.
Gordon H. Williams, MD
Brigham and Women's Hospital
William F. Young, Jr., MD
Last revised: April 2013