[Clinical significance of apolipoprotein B-48 (apoB-48) in patients with thyroid disease]

Apolipoprotein B-48 (apoB-48) is a constituent of chylomicrons and chylomicron remnants, and its serum concentration is thought to be one of the risk factors for atherosclerosis. Clinically overt hypothyroidism (OH) has been associated with accelerated and premature coronary atherosclerosis. In the current study, we measured the serum apoB-48 concentration in patients with hyperthyroidism and hypothyroidism. We also evaluated the correlations between serum apoB-48 and thyroid hormones, from which a clinical significance of apoB-48 measurement in thyroid disease was deduced. Serum apoB-48 concentration was measured by chemiluminescence enzyme immunoassay (CLEIA) and it correlated with thyroid stimulating hormone (TSH), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) and triglycerides(TG), but negatively correlated with free thyroxine (FT4) and free triiodothyronine (FT3). In a cross-sectional study, serum apoB-48 concentrations were significantly higher in OH subjects (8.4 +/- 5.4 microg/ml) compared to those in 70 hyperthyroid subjects (5.0 +/- 3.9 microg/ml) and 50 normal subjects (6.3 +/- 4.9 microg/ml). After L-T4 replacement, serum apoB-48 concentrations were decreased in OH patients. However, these changes were smaller compared to those of TSH, FT4 and FT3. Serum apoB-48 levels and thyroid hormones and lipid profiles were measured in 31 SH patients and 34 normal subjects. Significant difference was noted in serum apoB-48, TG and TSH between patients with SH and normal. In conclusion, serum apoB-48 concentration depends on thyroid status like TC, LDL-C and TG. Thyroid hormone replacement therapy may reduce serum apoB-48 concentrations in patients with OH. Therefore, increased serum apoB-48 concentrations may contribute to the increased risk of atherosclerosis and premature coronary artery disease in the hypothyroid state.