Re: 'Effects of Short-Term Hypothyroidism on the Lipid Transfer to High-Density Lipoprotein and Other Parameters Related to Lipoprotein Metabolism in Patients Submitted to Thyroidectomy for Thyroid Cancer' by Sigal et al. (Thyroid 2019;29:53-58)

摘要

Dear Editor: The profound effects of hypothyroidism on lipoprotein metabolism have been known for decades. Such effects include high-density lipoprotein (HDL) cholesterol elevations, as confirmed in the recent study by Sigal et al. (1). Given the well-established inverse association of HDL cholesterol concentrations with atherosclerotic cardiovascular disease, there is continued interest in discerning the mechanisms that contribute to changes in HDL that occur during hypothyroidism. Among other pathways, the cho-lesteryl ester transfer protein (CETP)-mediated transfer of cholesteryl esters from HDL to apolipoprotein B-containing (triglyceride-rich) lipoproteins provides a key regulatory step in HDL metabolism. High HDL cholesterol levels are observed in genetic CETP deficiency, whereas HDL cholesterol increases consequent to pharmacological CETP inhibition (2). As appreciated by Sigal et al., several previous studies have demonstrated that hypothyroidism may decrease plasma cholesteryl ester transfer (CETP) mass or activity, measured either as the transfer of radiolabeled cholesteryl esters from endogenous HDL toward apolipoprotein B-containing (triglyceride-rich) lipoproteins (referred to in the study by Sigal et al.) (1), or as the transfer/ exchange of radiolabeled cholesteryl esters between ex-ogenously added low density lipoproteins and HDL (3), the latter type of assay reflecting the plasma level of active CETP independent from the endogenous plasma lipoproteins (3). In general, these earlier findings are consistent with an effect of low thyroid hormone status to impair the CETP-mediated cholesteryl ester transfer process, thereby conceivably contributing to an increase in HDL cholesterol.