Decrease in serum levels of thyroid hormone in patients with coronary heart disease.

The aim of this study was to evaluate the relationship between subclinical hypothyroidism and/or autoimmune thyroid disease and coronary heart disease (CHD). Ninety seven patients diagnosed as having CHD by a coronary angiography (CHD group) and 103 healthy subjects matched for age, sex and body mass index (control group) were included in the study. Thyroid function, thyroid autoantibodies and serum lipid concentrations were measured in the CHD and control groups. The CHD group exhibited significantly decreased serum free T3 (FT3) and free T4 (FT4) levels, and significantly increased serum TSH levels as compared with the control group, indicating a significant decrease in thyroid function in the CHD patients. Serum high density lipoprotein cholesterol (HDL-C) levels were significantly decreased in the CHD group. The incidence of subclinical hypothyroidism and thyroid autoantibodies was similar in both two groups. These observations were also true of women even after those who had diabetes mellitus (DM), hypertension (HT) and a smoking habit were excluded. This was not the case, however, in men without DM, HT, or a smoking habit. Patients with CHD had significantly lower serum levels of HDL-C than the control subjects, regardless of gender (P < 0.01). In the group with CHD, there was no difference between the serum lipid levels in patients with subclinical hypothyroidism and those with normal thyroid function. Female patients with CHD had significantly lower serum levels of thyroid hormone and HDL-C, but their subclinical hypothyroidism or thyroid autoimmunity did not seem to be related to the development of CHD.