Differences in HDL particle size in the presence of subclinical thyroid dysfunctions: The ELSA-Brasil study.

Background and Aims: Thyroid dysfunction is related to several lipid abnormalities. There is no consensus about concentration of high-density lipoprotein (HDL) in different studies. The aim of this report is to evaluate HDL particle (HDL-P) subfractions across a spectrum of thyroid functions in a Brazilian population.
Methods: Individuals were divided into three groups by baseline thyroid function (subclinical hypothyroidism, euthyroidism, and subclinical hyperthyroidism). HDL-P subfractions were analyzed by Nuclear Magnetic Resonance (NMR) spectroscopy. To examine the association between HDL-P subfractions and thyroid function, we used univariate and multivariate linear regression models adjusted for demographic characteristics, comorbidities, lifestyle factors, and traditional lipid measurement (HDL-C, LDL-C and triglycerides).
Results: Of 3304 participants, 54.1% were women, 51.2% white, with mean age 50.6 ± 8.7 years. HDL-C and triglycerides levels (p = 0.032 and p = 0.016, respectively) were higher in the SC hypothyroid group. There were no statistically significant differences in total cholesterol levels and LDL-C levels. In univariate analysis, small HDL-P subfractions were significantly lower in subclinical hypothyroidism (p = 0.026) whereas intermediate HDL-P were higher in subclinical hyperthyroidism (p = 0.049), compared to euthyroidism. After adjustment for demographic data, SC hypothyroidism was still statistically associated with lower levels of small HDL-P. After adjusting for comorbidities, lifestyle factors, and traditional lipid measurements, SC hypothyroidism had an established association with lower levels of small HDL-P while SC hyperthyroidism was associated with lower levels of large HDL-P.
Conclusions: In this large cohort from a Brazilian population, subclinical hypothyroidism was associated with lower small HDL-P subfractions, and subclinical hyperthyroidism with lower large HDL-P subfractions and higher intermediate HDL-P subfractions.
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