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Elevated TSH levels may be associated with adverse lipid profile
A modest association may exist between elevated thyroid-stimulating hormone levels and an adverse lipid profile, but a link could not be confirmed longitudinally, according to researchers.
“Earlier studies have also shown ample evidence of a cross-sectional association between thyroid function and lipids,” Ville L. Langén, of the National Institute for Health and Welfare in Helsinki, and colleagues wrote. “However, it remains difficult to draw causal inference solely based on cross-sectional studies, and longitudinal epidemiological studies on this topic are remarkably scarce.”
In a prospective study, Langén and colleagues analyzed data from 5,205 adults aged at least 30 years examined in 2000-2001 as part of the Health 2000 survey in Finland (mean age, 52 years; 53% women); 2,486 were re-examined 11 years later and included in longitudinal analyses. Participants completed interviews and physical exams and provided blood samples for lipid profile measurements. Researchers used linear regression analyses adjusted for age, sex, smoking status and BMI to assess the associations of baseline TSH and TSH categories (low, reference range and high) with total cholesterol, HDL cholesterol, LDL cholesterol, apolipoprotein A-I and ApoB and triglycerides at baseline and follow-up.
Researchers found that, at baseline, higher TSH levels were associated with higher total cholesterol (P < .001), LDL cholesterol (P = .002), ApoB (P < .001) and log triglycerides (P = .004), but not with other lipid outcomes after multivariable adjustment.
At the 11-year follow-up, higher baseline TSH was associated with higher total cholesterol (P = .033), LDL cholesterol (P = .015) and ApoB (P = .028) in women, but not men.
Participants with high TSH at baseline had a 0.22 mmol/L (95% CI, 0.02-0.41) higher LDL cholesterol at follow-up (P = .028) than participants with TSH in the reference range (0.4-3.4 mU/L).
After excluding participants with high-risk baseline lipid values, the longitudinal association did not persist, according to researchers (P > .098).
“In our additional analyses restricted to the reference range of TSH, we surprisingly found that higher baseline TSH was associated with a more favorable follow-up lipid profile in women in terms of HDL cholesterol and in men in terms of total and LDL cholesterol,” the researchers wrote. “Some of these findings from the analyses restricted to the reference range of TSH could be coincidental. From a clinical perspective, these longitudinal results are at any rate inconsistent with the hypothesis of benefit of thyroid hormone replacement therapy even in patients having high normal TSH values.”
The researchers noted that there were no follow-up TSH level data available for analyses, which impedes any interpretation of longitudinal results. In addition, any participants on lipid-lowering, antithyroid or thyroid hormone replacement medications were excluded, resulting in a follow-up sample that was only 48% of the baseline sample. – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.