Plasma CRP, apolipoprotein A-1, apolipoprotein B and Lpa levels according to thyroid function status

Altered lipid profile is a well-known manifestation of thyroid dysfunction. Recently, serum Lp(a) and C-reactive protein (CRP) have emerged as new cardiovascular risk factors, but studies on changes of these markers with respect to thyroid function status have produced variable results. To better understand the effects of thyroid dysfunction on the development of atherosclerosis, we investigated plasma CRP and lipid profiles such as apoA1, apoB, and Lp(a) in cases with differing severities of thyroid dysfunction.

Fifty four patients with hyperthyroidism, 35 patients with subclinical hyperthyroidism, 33 patients with overt hypothyroidism, 190 patients with subclinical hypothyroidism and 100 age- and sex-matched healthy control subjects were evaluated. Serum high sensitivity (hs)-CRP and Lp(a) were measured by immunonephelometry.

No significant differences were found in serum hs-CRP, Lp(a), HDL-C or ApoA1 in different thyroid function groups. Serum total cholesterol and LDL-C levels were significantly lower in cases of hyperthyroidism than in cases of overt hypothyroidism, subclinical hypothyroidism or subclinical hyperthyroidism, or in healthy control subjects (p <0.01). Serum triglyceride levels were higher in overt hypothyroidism than in hyperthyroidism or healthy controls (p <0.05). Serum apoB levels were significantly lower in hyperthyroidism than in overt hypothyroidism, subclinical hypothyroidism or in healthy control subjects (p <0.01). These differences were consistently significant after adjustment for age and BMI.

Serum CRP and Lp(a) levels, risk factors for atherosclerosis, were not found to be significantly affected by the degree of thyroid dysfunction. Increased risk of atherosclerosis in hypothyroidism does not appear to be associated with non-traditional cardiovascular risk factors, such as serum CRP, Lp(a) or apoA1 levels.