On the rise in low density and high density lipoproteins in response to the treatment of hypertriglyceridaemias in type IV and type V hyperlipoproteinaemias.

In Type V hyperlipoproteinaemia the concentration of LDL and HDL cholesterol is low. When the hypertriglyceridaemia is normalized, either by diet or micotinic acid, both LDL and HDL increase. In Type IV hyperlipoproteinaemia both LDL and HDL cholesterol decrease with increasing VLDL levels. During treatment of Type IV the change in LDL cholesterol is linearly related to the pretreatment LDL concentration so that higher LDL levels will fall and the lower will rise. HDL levels will also rise. The fall in VLDL during treatment is rapid and the rise in LDL also occurs rapidly indicating a relationship between these two reciprocal changes. HDL cholesterol, however, however, remains constant some time after VLDL has reached its lowest level and the rise occurs later indicating another mechanism than for LDL. These changes in the three major lipoprotein classes deserve clinical attention. While both the fall in VLDL and the rise in HDL may be benefical from the point of view of atherosclerosis the rise in LDL may be harmful. These is at present no way to evaluate the effect of these complex changes. However, these findings stress the imporance of considering changes in lipoprotein levels and not only in total serum triglycerides and cholesterol during treatment of hyperlipoproteinaemia.