Abstract
Iodine is an essential component of the thyroid hormone which plays crucial roles in healthy thyroid function and lipid metabolism. However, the association between iodine status and dyslipidemia has not been well established at a population level. We aimed to test the hypothesis that the odds of dyslipidemia including elevated total cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol and apolipoprotein B, and lowered high-density lipoprotein (HDL) cholesterol and HDL/LDL ratio are associated with urinary iodine concentration (UIC) in a population perspective. Data of 2495 US adults (≥20 years) in the National Health and Nutrition Examination Survey 2007–2012 were used in this study. Two subgroups (i.e., UIC below vs. above the 10th percentile) were compared of dyslipidemia as defined based on NCEP ATP III guidelines. The differences between the groups were tested statistically by chi-square test, simple linear regressions, and multiple logistic regressions. Serum lipid concentrations differed significantly between two iodine status groups when sociodemographic and lifestyle covariates were controlled (all, p < 0.05). Those with the lowest decile of UIC were more likely to be at risk for elevated total cholesterol (>200 mg/dL) (adjusted odds ratio (AOR) = 1.51, 95% confidence interval (CI): 1.03–2.23) and elevated LDL cholesterol (>130 mg/dL) (AOR = 1.58, 95% CI: 1.11–2.23) and lowered HDL/LDL ratio (<0.4) (AOR = 1.66, 95% CI: 1.18–2.33), compared to those with UIC above the 10th percentile. In US adults, low UIC was associated with increased odds for dyslipidemia. Findings of the present cross-sectional study with spot urine samples highlight the significant association between UIC and serum lipids at population level, but do not substantiate a causal relationship. Further investigations are warranted to elucidate the causal relationship among iodine intakes, iodine status, and serum lipid profiles.
Highlights
Iodine is an indispensable component of thyroid hormone biosynthesis and normal thyroid function [1]
Since every cell in the body is affected by thyroid hormone, iodine status is associated with various health outcomes including goiter, hypothyroidism, mental retardation, and dyslipidemia [3]
Sex, age, and BMI explained the largest portion of the variability in the majority of serum lipid biomarkers; and other sociodemographic and lifestyle variables accounted for little variance in most serum lipid biomarkers
Summary
Iodine is an indispensable component of thyroid hormone biosynthesis and normal thyroid function [1]. Since every cell in the body is affected by thyroid hormone, iodine status is associated with various health outcomes including goiter, hypothyroidism, mental retardation, and dyslipidemia [3]. In an iodine deficient population, serum thyroid stimulating hormone (TSH) levels is elevated to prompt an uptake of circulating iodine by the thyroid [5]. Abnormal thyroid hormone due to iodine deficiency may lead to adverse aftereffects such as hypothyroidism throughout various life stages [7]. It is well-known that hypothyroidism is a major risk factor for the development of dyslipidemia, hypercholesterolemia and cardiovascular disease (CVD) [8,9]. Hypothyroidism accelerates elevations in serum total cholesterol and low-density lipoprotein (LDL) cholesterol by increasing cholesterol absorption in the intestines
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