Effect of hypothyroidism on blood lipid concentrations in horses
Frank, N.; Sojka, J.E.; Latour, M.A.; McClure, S.R.; Polazzi, L.
American Journal of Veterinary Research 60(6): 730-733
1999
ISSN/ISBN: 0002-9645 PMID: 10376902 Document Number: 511723
Five healthy adult (euthyroid) mares were used to measure and compare concentrations of selected blood lipids before and after thyroidectomy in horses. Thyroidectomy was performed, and hypothyroidism confirmed. Selected blood lipid variables were measured before hypothyroidism was induced and weekly for 4 weeks after induction. Plasma concentrations of very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), serum triglyceride (TG), total cholesterol (TC), and nonesterified fatty acid (NEFA) were measured. The composition of VLDL and LDL also was examined. Mean plasma concentrations of VLDL and LDL increased significantly after thyroidectomy. By 4 weeks after thyroidectomy, a ninefold increase in mean plasma concentration of VLDL and a threefold increase in LDL, compared with baseline values, were detected. After thyroidectomy, mean percentage of TG in VLDL increased significantly, whereas free cholesterol and cholesterol ester content decreased. Mean percentage of TG in LDL also increased by 3 to 4 weeks after thyroidectomy. Serum concentrations of TG and TC increased, whereas serum NEFA concentration decreased. It is concluded that hypothyroidism significantly alters blood lipid concentrations of horses. After thyroidectomy, high VLDL concentration, appearance of TG-rich VLDL, increased serum concentrations of TG and TC, and decreased blood concentration of NEFA were evident. Examination of blood lipid concentrations of horses may be useful for detecting naturally acquired hypothyroidism.