There are two main types of cholesterol: HDL (good) cholesterol and LDL (bad) cholesterol:
HDL stands for high-density lipoproteins. It is called the "good" cholesterol because it carries cholesterol from other parts of your body back to your liver. Your liver then removes the cholesterol from your body. LDL stands for low-density lipoproteins. It is called the "bad" cholesterol because a high LDL level leads to a buildup of cholesterol in your arteries.
A blood test can measure your cholesterol levels, including HDL. When and how often you should get this test depends on your age, risk factors, and family history. With HDL cholesterol, higher numbers are better, because a high HDL level can lower your risk for coronary artery disease and stroke. How high your HDL should be depends on your age and sex:
Age 19 or younger More than 45mg/dl
Men age 20 or older More than 40mg/dl
Women age 20 or older More than 50mg/dl
If your HDL level is too low, lifestyle changes may help. These changes may also help prevent other diseases, and make you feel better overall: Eat a healthy diet, stay at a healthy weight, exercise, avoid cigarettes, and limit alcohol.
Some cholesterol medicines, including certain statins, can raise your HDL level, in addition to lowering your LDL level. Health care providers don't usually prescribe medicines only to raise HDL. But if you have a low HDL and high LDL level, you might need medicine.
Taking certain medicines can lower HDL levels in some people. They include beta blockers, a type of blood pressure medicine; anabolic steroids, including testosterone, a male hormone, progestins, which are female hormones that are in some birth control pills and hormone replacement therapy; and benzodiazepines, sedatives that are often used for anxiety and insomnia. If you are taking one of these and you have a very low HDL level, ask your provider if you should continue to take them. Diabetes can also lower your HDL level, so that gives you another reason to manage your diabetes.
Your body manufactures 75% of your cholesterol, only 25% is from the diet. HDL cholesterol is not good and LDL cholesterol is not bad. One begets the other – LDL cholesterol is released from the liver as a response to inflammation. It is then taken into the cells of the body and used to make hormones and other needed chemical compounds. Some of the LDL is modified, then released back into the blood stream as HDL. It does indeed travel back to the liver where it is converted back to LDL and the cycle starts over.
Several years ago Pfizer had to stop human trials on a drug that raised HDL while lowering LDL as too many of the subjects suffered cardiac events. Recent studies have also indicated that elevated HDL levels do increase the risks of heart attack.
Finally, if your HDL level is higher than your LDL level, that is an indication of autoimmune disease.
I no longer try to manipulate serum lipid levels. A balance in the LDL and HDL levels should be achieved by reducing systemic inflammation. The key is to identify the source and pathway for the inflammation. Treat the inflammation and the LDL and HDL levels will fall in line.
Source: December 27, 2018 NIH