Serum high-density lipoprotein cholesterol concentrations in hypo- and hyperthyroidism.

We studied alterations in the concentration of high-density lipoprotein cholesterol and of other lipid categories (total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, and triglycerides) in serum in hypo- and hyperthyroid states, and compared these findings with those of a control group. In the latter group the lipids showed an age-related increase in concentration but with a decrease in the eighth decade in all categories. In untreated hypo- and hyperthyroid subjects, all of the lipid values differed significantly from those of the controls but promptly returned to normal values upon treatment. In hypothyroid patients who are prone to develop coronary heart disease, the concentrations of high-density lipoprotein cholesterol were high, suggesting protection against heart disease, while the ratio to total cholesterol indicated the contrary. The exact opposite of these relationships was seen in hyperthyroid disorders. This apparent paradox suggests that the low-density lipoprotein cholesterol in serum, with its established atherogenic effect, should be given at least equal, if not more, weight than the concentration of high-density lipoprotein cholesterol in serum, with its alleged protective effect.