High-density lipoprotein cholesterol, hepatic lipase and lipoprotein lipase activities in thyroid...

We have investigated the effects of hyper- and hypothyroidism (clinical and subclinical) on lipid metabolism, with special emphasis on serum high-density lipoprotein cholesterol, post-heparin plasma hepatic lipase and lipoprotein lipase activities. In 16 patients with hyperthyroidism, increased post-heparin plasma hepatic lipase activity, decreased serum total cholesterol and serum high-density lipoprotein cholesterol were found while lipoprotein lipase activity and serum triglyceride were normal. In six patients with overt hypothyroidism serum total cholesterol and triglyceride were increased, post-heparin plasma hepatic lipase and lipoprotein lipase were decreased while serum high-density lipoprotein cholesterol was normal. In six patients with subclinical hypothyroidism, serum total cholesterol was increased, serum high-density lipoprotein cholesterol was decreased, while serum triglyceride, post-heparin plasma hepatic lipase and lipoprotein lipase were normal. When the three groups of patients became euthyroid, serum total cholesterol, serum triglyceride, post-heparin plasma hepatic lipase, lipoprotein lipase, and serum high-density lipoprotein cholesterol reverted to normal except for serum high-density lipoprotein cholesterol in the hyperthyroid group which showed no significant change with treatment. A positive correlation was found between serum T3 and post-heparin plasma hepatic lipase while negative correlations were found between serum total cholesterol and serum T3, post-heparin plasma hepatic lipase and serum total cholesterol, lipoprotein lipase and serum triglyceride respectively. Thus in these patients with thyroid dysfunction, significant reversible alterations in serum total cholesterol, triglyceride and high-density lipoprotein cholesterol were found and could be correlated with the observed changes in the activities of hepatic lipase and lipoprotein lipase.