EFFECT OF THYROID-HORMONE REPLACEMENT ON LIPOPROTEIN(A), LIPIDS, AND APOLIPOPROTEINS IN SUBJECTS WITH HYPOTHYROIDISM

Objective: To study the effect of thyroid hormone replacement on total cholesterol, low-density lipoprotein cholesterol, triglycerides, high -density lipoprotein cholesterol (HDL-C), apolipoprotein A-I and B-100 , arid lipoprotein(a) [Lp(a)] in subjects with hypothyroidism. Materia l and Methods: In 17 patients with clinical primary hypothyroidism, st udies were done before, and after thyroid hormone replacement therapy. Free thyroxine and thyrotropin were determined by chemiluminescent as say. Total cholesterol and triglycerides were measured by enzymatic me thods, and HDL-C was measured after dextran sulfate-MgCl2 precipitatio n. Apolipoprotein A-I and B-100 were assayed by immunonephelometry, Fo r measurement of Lp(a), we used a sequential sandwich enzyme-linked im munosorbent assay. Results: After levothyroxine treatment, the mean co ncentration of thyrotropin decreased from 91.4 to 3.7 mu IU/mL, and fr ee thyroxine increased from 0.5 to 1.2 ng/dL. Total cholesterol, trigl ycerides, HDL-C, low-density lipoprotein cholesterol, and apolipoprote in A-I and B-100 decreased after thyroid hormone replacement therapy. Lp(a) levels also decreased significantly (P<0.05) after treatment, fr om a mean of 33.4 to 25.6 mg/dL, Conclusion: Hypothyroidism is associa ted with an increase in total cholesterol, triglycerides, HDL-C, apoli poprotein A-I and B-100, and Lp(a). A reduction in lipid and lipoprote in levels after thyroid hormone replacement in our study cohort result ed in a less atherogenic profile.