LDL stands for low density lipoprotein. LDL transports cholesterol to all cells throughout the body, which is why it is considered bad cholesterol.
The main structural difference between LDL and HDL would be the composition of the two. LDL is made up of 25% protein and 50% cholesterol. While, HDL is 20% cholesterol and 50% protein.
Physicians monitor HDL and LDL concentrations because too much LDL can result in cholesterol plaques forming in the bloodstream. High levels of LDL can also lead to an increased risk for a heart disease.