Abstract 20246: Impact of Subclinical Hypothyroidism on Lipid and Lipoprotein Subclasses
Background: It is uncertain whether subclinical hypothyroidism (SCH) is associated with lipid abnormalities. Therefore, we examined a range of lipid and lipoprotein subclasses across the spectrum of euthyroid, SCH, and overt hypothyroidism (HT) in apparently healthy women free of CVD.
Methods: A random sample of 3914 individuals from the Women’s Health Study was selected for thyroid function analysis. From this sample, 3321 individuals were not on lipid lowering therapy and had thyroid profiles compatible with euthyroid, 2571 (77.4%); SCH, 573 (17.3%); and HT, 177 (5.3%). Lipids were measured directly, and lipoprotein subclasses were measured by nuclear magnetic resonance spectroscopy. Statistical comparison was performed by ANOVA, after adjusting for age, BMI, menopausal status, HRT, blood pressure, anti-hypertensive medication, diabetes, and current smoking.
Results: Compared with euthyroid individuals, those with SCH and HT were older, had higher BMI, greater prevalence of post-menopausal status and metabolic syndrome, and lower prevalence of smoking. They also had higher triglycerides and lower HDL-C, but similar LDL-C (Table). More detailed lipoprotein phenotyping showed that SCH and HT were associated with an insulin resistant lipoprotein subclass profile. Going from euthyroid to SCH to HT, there was a graded increase in concentrations of VLDL particles (mainly due to large and medium VLDL), reflected by larger VLDL size; higher concentration of LDL particles as well as apolipoprotein B concentration despite no difference in LDL-C; and higher concentration of small HDL particles. Similarly, the lipoprotein insulin resistance score of SCH and HT was worse than euthyroid.
Interpretation: In this large population of apparently healthy women, individuals with SCH had differences in the lipid and lipoprotein subclass profile that indicated worsening insulin resistance compared with euthyroid individuals, despite having similar LDL-C and total cholesterol.
Author Disclosures: P.H. Harada: None. J.E. Buring: None. S. Mora: Research Grant; Significant; Astra Zeneca, Atherotech Diagnostics, NHLBI. Consultant/Advisory Board; Modest; Quest Diagnostics, Cerenis Therapeutics, Lilly, Sanofi-Genzyme.
- © 2014 by American Heart Association, Inc.