Serum lipids, "double pre-beta lipoproteinemia", and distribution of the apo-very-low density (VLDL) lipoprotein peptides in hypothyroid patients before and after substitution therapy

Thirty-six hypothyroid patients had total thyroidectomy for cancer. Thirty of them were studied before and during hormone replacement therapy, 1-1 .1 microgram/kg triiodothyronine (T3) per day. Mean treatment period was 90 days. During treatment mean serum total cholesterol (TC), triglycerides (TG), the ratio of TC to TG in very-low-density lipoprotein and the prevalence of the "double pre-beta VLDL lipoproteinemia" (Double-PBL) were significantly reduced as compared to the pretreatment values. The VLDL peptides were separated bysoelectric focusing (IEF) in polyacrylamide gel. The relative content of apolipoprotein E (arginine-rich apoprotein) and the E/C-peptides ratio were significantly reduced after T3 therapy. On the contrary, the content of C11 peptide was significantly increased. Apoprotein E was positively correlated with serum TC. The proportion of the intermediate density lipoprotein fraction, evaluated by agarose gel electrophoresis, consistently decreased after treatment. The results of our study suggest that thyroid hormones affect the metabolism of remnant lipoproteins.