High density lipoprotein and arteriosclerosis. Different patterns in primary hypothyroidism and type IIa hyperlipoproteinemia.

Concentrations of high density lipoprotein (HDL) and its subfractions were contrasted in two groups of patients with hypercholesterolemia and a control group of normocholesterolemic subjects. HDL-cholesterol and HDL-protein were low in patients with Type IIa hyperlipoproteinemia, but elevated in patients with primary hypothyroidism. HDL-3 levels were low whereas those of HDL-2 remained unchanged in patients with Type IIa hyperlipoproteinemia. In contrast, in the hypothyroid patients, HDL-3 remained unchanged, while HDL-2 levels were high. The role of HDL in the development of arteriosclerosis in patients with primary hypothyroidism is therefore questioned. Our findings also suggest that measurement of HDL-cholesterol alone cannot be regarded as an accurate indicator of changes in total HDL concentration in different clinical situations.