Abstract P490: Subclinical Thyroid Disorders and Triglyceride-rich Lipoprotein Particles Concentration. ELSA-Brasil Cohort

Background: Subclinical thyroid disorders have been associated with atherosclerosis and increased cardiovascular risk. Subclinical hypothyroidism is associated with higher levels of total cholesterol and Low-density lipoprotein cholesterol as well as high levels of triglycerides and low levels of high-density lipoprotein cholesterol. Triglyceride-rich Lipoprotein Particles concentration (TRLP) have recently emerged as a causal factor for atherogenesis. Aim: To evaluate the relationship between Subclinical Hypothyroidism and Subclinical Hyperthyroidism and Triglyceride-rich Lipoprotein Particles. Methods: Participants from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) were classified according to the baseline thyroid function as Subclinical Hypothyroidism, Euthyroidism, and Subclinical Hyperthyroidism. Conventional lipid concentrations (total, HDL cholesterol, and triglycerides were determined by a nonprecipitated colorimetric method. The TRLP subfractions were analyzed through Nuclear Magnetic Resonance spectroscopy. To examine the association between TRLP subfractions and thyroid function, we conducted a multivariate linear regression model adjusted for demographic characteristics (race, gender, and educational level), body-mass index, diabetes, smoking status, and alcoholic beverages intake. Results: Of 3,550 individuals free of cardiovascular or thyroid diseases (54%, women; median age 51 years; 51% White, and 53% with at least college education) 92%of them were euthyroid, 6.8% had subclinical hypothyroidism, and 1.2% had subclinical hyperthyroidism. No differences were observed concern the levels of total, HDL, and LDL-cholesterol, but triglycerides were higher for people with Subclinical Hypothyroidism. After adjustment by the covariates described above and using subjects with normal thyroid function as the reference group, for people with Subclinical hypothyroidism a difference of means ( and 95% Confidence Interval) for Total TRLP levels (in ng/L) obtained was 0.06 (-0.00 to 0.13), and for the TRLP subfractions elevated for Very-Small [0.16 (0.02 to 0.28)] and Very-Large [0.21 (0.05 to 0.36)], and similar values for Small [-0.01 (-0.13 to 0.12)]; Medium [0.05 (-0.08 to 0.17)] and Large [0.16 (-0.06 to 0.38)] subfractions. In Subclinical Hyperthyroidism, there was a reduction in Total TRLP (-0.24 (-0.40 - -0.08)), seemingly driven by reduced Very Small-TRLP (0.23 (-0.11 - 0.57). Conclusion: This study suggests that subclinical hypothyroidism is associated with high levels of Very-Small and Very-Large TRLP, which are related to an unfavorable atherogenic profile. Subclinical Hyperthyroidism is associated with low concentrations of Very-Small TRLP.