Low Density Lipoprotein: Definitions

Daniel Kreimer: Is not this the killer? Yes, gentle reader, we have reached the lair of the dark lord himself. This is the substance guilty of wiping out millions of people each and every year. For LDL is also known ‘bad’ cholesterol. Even though, of course, it is not cholesterol at all. So stop calling it cholesterol ! Sorry, that does not mean you. I am ranting here at scientists, doctors and the healthcare profession in general. No wonder everyone is confused, when the terminology used is completely bonkers: A chylomicron is a lipoprotein, but it is never called that.

A VLDL is a lipoprotein but it is usually called a triglyceride. A LDL is a lipoprotein but it is called ‘bad’ cholesterol. A high density lipoprotein (HDL), the smallest lipoprotein, is called ‘good’ cholesterol. I am a little teapot short and stout; lift me up and pour me out. Actually, just to make things even more confusing, if that were possible, there is another form of LDL. Yes, I am afraid so.

It is exactly the same as LDL, apart from one thing. It has two types of protein attached to the outside. (All lipoproteins have proteins attached to their outer surface. This is how receptors on cells throughout the body recognise them.) This form of lipoprotein, however, is called lipoprotein (a). Good heavens, a lipoprotein that is called a lipoprotein, it must be some sort of a record. Anyway,this lipoprotein is usually pronounced as ‘el pee little A’ and written as Lp(a).

Almost no one, including 99 per cent of doctors, knows that Lp(a) is actually LDL. Even though this fact is of fundamental importance to understanding heart disease. (More on this later.) Why Lp(a) is not  called LDL(a), or something of the sort? Because then everyone would know what it was, and that would never do. (By the way, no one ever tells you what your Lp(a) level is. Which is typical, as it is the only one that may actually be important.) I have just realized that I have been remiss in not mentioning high density lipoproteins, or HDL, or ‘good’ cholesterol. This lipoprotein, it is thought, is mainly manufactured in the liver. (What do you mean ‘thought: surely all this stuff is known?’ Sorry, no it is not.) Anyway, it is believed that HDL ‘removes’ cholesterol from plaques in arteries and transports it back to the liver for reprocessing. So HDL protects you from heart disease and is therefore ‘good’: Even if it is not cholesterol, and, pound for pound, contains more cholesterol than any other sort of lipoprotein in the body.