Hypothyroidism is associated with an increased risk of coronary artery disease. This observation may in part be related to the lipid abnormalities in patients with this condition. The lipid profiles of 268 patients with primary hypothyroidism and 27 with secondary hypothyroidism, who were examined in the Thyroid Clinic at the Mayo Clinic during a L-year period, were reviewed. Hyperlipidemia was commonly associated with both primary and secondary hypothyroidism. The lipid values decreased with treatment of hypothyroidism. Type IIa hyperlipidemia was the most common lipid abnormality in patients with primary hypothyroidism, whereas type lIb was the most common in those with secondary hypothyroidism. Totallhigh-density lipoprotein cholesterol and low-density lipoprotein! high-density lipoprotein cholesterol ratios were increased in both male and female patients with primary and secondary hypothyroidism, and they decreased with restitution of the euthyroid state, although this decrease achieved statistical significance only in female patients. Significant associations with total thyroxine were noted for total cholesterol and triglycerides and with thyroid-stimulating hormone (thyrotropin) for total cholesterol and low-density lipoprotein cholesterol. Thus, both primary and secondary hypothyroidism are commonly associated with an atherogenic lipid profile, which improves with replacement of thyroid hormone. Even after restitution of the euthyroid state, however, the lipid profile remains atherogenic in male patients. In comparison with primary hypothyroidism, the lipid profile is more atherogenic in secondary hypothyroidism because of the lower high-density lipoprotein cholesterol levels associated with this condition.
Hypothyroidism is associated with coronary artery disease, 1 and lipid abnormalities are known to have a crucial role in atherogenesis.' Hyperlipidemia occurs in patients with hypothyroidism;' the association between coronary artery disease and hypothyroidism may be mediated by these lipid abnormalities.
That total and low-density lipoprotein (LDL) cholesterol levels are increased in patients with hypothyroidism is well known.' Not so widely appreciated, however, is that such patients have also been found to have increased high-density From the Division of Endocrinology/Metabolism and Internal Medicine (T.O., S.F.D., P.J.P.) and Section of Biostatistics (P.C.O.),