The cytochrome P450s (CYPs), a large diverse heme-containing enzyme superfamily with a large number of members, are found across all organisms in prokaryotic and eukaryotic worlds from animals, plants, fungi, protists, bacteria, and archaea to viruses. These proteins contain unusual reduced carbon monoxide difference spectrum that exhibits a Soret peak at 450 nm, thus called "Pigment at 450 nm" or "P450". The unique spectral peak is produced by a thiolate anion acting as the fifth ligand to the heme. This peak is a unique feature only observed in four classes of hemoproteins, namely, P450s, nitric oxide synthases, chloroperoxidases, and protein H450.

Cytochrome P450 2D6 (Cytochrome P450 family 2 subfamily D member 6) is an enzyme that in humans is encoded by the CYP2D6 gene. The gene is located near two cytochrome P450 pseudogenes on chromosome 22q13.1. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. CYP2D6 is primarily expressed in the liver. It is also highly expressed in areas of the CNS, including the substantia nigra.

Human CYPs are primarily membrane-associated proteins located either in the inner membrane of mitochondria or in the endoplasmic reticulum of cells. CYPs metabolize thousands of endogenous and exogenous chemicals. Some CYPs metabolize only one (or a very few) substrates, such as CYP19 (aromatase), while others may metabolize multiple substrates. Both of these characteristics account for their central importance in medicine. Cytochrome P450 enzymes are present in most tissues of the body, and play important roles in hormone synthesis and breakdown (including estrogen and testosterone synthesis and metabolism), cholesterol synthesis, and vitamin D metabolism. Cytochrome P450 enzymes also function to metabolize potentially toxic compounds, including drugs and products of endogenous metabolism such as bilirubin, principally in the liver.

Cholesterol is a waxy, fat-like substance that's found in all cells of the body. Your body needs some cholesterol to make hormones, vitamin D, and substances that help you digest foods. Your body makes all the cholesterol it needs. However, cholesterol also is found in some of the foods you eat.

Cholesterol travels through your bloodstream in small packages called lipoproteins. These packages are made of fat (lipid) on the inside and proteins on the outside.

There are several types of lipoproteins in the blood. In order of increasing density, they are Ultra Low Density Lipoproteins (ULDL) or Chylomicrons, Very Low Density Lipoproteins (VLDL), Intermediate Density Lipoproteins (IDL), Low Density Lipoproteins (LDL), and High Density Lipoproteins (HDL).

LDL cholesterol sometimes is called "bad" cholesterol. A high LDL level leads to a buildup of cholesterol in your arteries. (Arteries are blood vessels that carry blood from your heart to your body.)

HDL cholesterol sometimes is called "good" cholesterol. This is because it carries cholesterol from other parts of your body back to your liver. Your liver removes the cholesterol from your body.

High blood cholesterol is a condition in which you have too much cholesterol in your blood. By itself, the condition usually has no signs or symptoms. Thus, many people don’t know that their cholesterol levels are too high. A blood test is the only way to detect high cholesterol. People who have high blood cholesterol have a greater chance of getting coronary heart disease, also called coronary artery disease.

Most diabetics with high blood pressure have no symptoms. However, very high blood pressure or rapidly rising blood pressure can cause:

• Headaches
• Vision problems
• Nose bleeds
• Trouble breathing
• Fits
• Black-outs

Similar to high blood pressure, the symptoms of low pressure may not always be apparent. If you do get symptoms, they may be identified as any of the following:

• Feeling dizzy, light headed or fainting
• Blurred vision
• A rapid or irregular heartbeat
• Feeling nauseous
• Confusion