HDL, LDL cholesterol levels associated with thyroglobulin antibody positivity
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Likelihood of testing positive for thyroglobulin antibodies is increased for people with higher LDL cholesterol and decreased for those with higher HDL cholesterol levels, particularly among women, according to study data.
“Few studies have explored the relationship between lipids and the positivity of thyroid autoantibodies,” Haixia Guan, MD, PhD, an endocrinologist in the department of endocrinology and metabolism at the First Hospital of China Medical University, and colleagues wrote in a study published in Endocrine. “Especially, recent data have shown that serum lipids are novel risk factors for developing autoimmune diseases, such as systemic lupus erythematosus, celiac disease, idiopathic thrombocytopenic purpura and Sjögren’s disease. Therefore, we aimed to evaluate whether similar associations can be observed in thyroid autoimmunity.”
Researchers conducted a retrospective cohort study of 6,456 people aged 14 years and older (51.1% female; mean age, 47.64 years) receiving thyroid function and antithyroid antibody testing during a routine medical exam at the First Hospital of China Medical University from January 2017 to December 2018. Data were collected from the hospital’s information system. All participants had normal thyroid-stimulating hormone levels. Serum TSH, thyroglobulin antibodies (TgAb) and thyroid peroxidase antibodies (TPOAb) were measured through same-day blood sampling collected in the morning after a fasting period of 8 to 12 hours.
There was an overall thyroid antibody positivity rate of 29.8% in the study population, with 42.4% of women having thyroid antibody positivity compared with 16.5% men. The most common thyroid antibody positive observed was in those who were positive for both TgAb and TPOAb.
After adjusting for age, gender, BMI, waist circumference, systolic blood pressure and fasting plasma glucose, each 1 mmol/L increase in LDL cholesterol was associated with a greater likelihood for TgAb positivity (OR = 1.14; 95% CI, 1.03-1.27; P = .011), and each 1 mmol/L increase in HDL cholesterol decreased the likelihood for TgAb positivity (OR = 0.77; 95% CI, 0.61-0.98; P = .035). No association was found between any lipid parameters and TPOAb positivity.
In subgroup analyses, women had a higher likelihood for TgAb positivity with increasing LDL cholesterol (OR = 1.16; 95% CI, 1.04-1.28; P = .007) and a lower likelihood with higher HDL cholesterol (OR = 0.77; 95% CI, 0.61-0.99; P = .037). No associations were found for men.
“The disparate results from gender could be related to the immune system exhibiting sexual dimorphism in humans,” the researchers wrote. “The unique effect of estrogen on the immune system may determine the susceptibility of women to autoimmune diseases and the greater immune response in women than in men. Furthermore, it is well established that smoking suppresses the immune system, the majority of males smoked whereas only a few women smoked may aid in interpreting the result.”
The researchers said the direction of any causal relationship cannot be verified due to the cross-sectional design of the study, and future prospective studies are needed to confirm the findings.
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