Alteration of Lipid Profile Between Subclinical Hypothyroidism and Well-Matched Controls: A Meta-Analysis

Abstract

In previous studies, subclinical hypothyroidism (SCH) has been associated with altered lipid profiles. However, since the discrepancy between these study results may reside in the great heterogeneity of the populations studied, this relationship is controversial. This study aimed to explore the changes in total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-c), and high-density lipoprotein cholesterol (HDL-c) between subclinical hypothyroidism (SCH) and well-matched euthyroid (EU) groups. Multiple databases were searched for publications before December 1, 2021, including cross-sectional studies on the association between SCH and lipid profile matched by age, gender, and BMI. Twenty-five articles with 3347 participants were included for meta-analysis. The results showed that the TC, TG, and LDL-c levels of the SCH groups were higher than the EU groups (TC, SMD = 0.49, 95% CI 0.27, 0.71, p < 0.001) (TG, SMD = 0.43, 95% CI 0.21, 0.64, p < 0.05 ) (LDL-c, SMD = 0.75, 95% CI 0.46, 1.03, p < 0.001 ). The HDL-c levels of the SCH group were lower than the control group (SMD = -0.53, 95% CI -0.81, -0.25, p < 0.05). SCH has a larger impact on LDL-c than the other three indicators. After subgroup analyses, there was a larger impact on lipid alteration in the subgroup of TSH > 10 μIU/ml, especially on LDL-c. This study found SCH was associated with altered lipid profiles. Appropriate clinical treatment may be needed to prevent dyslipidemia and related diseases.

Hypothyroidism, lipids, and lipidomics

“…The greater impact of higher TSH values with respect to producing a more adverse lipid profile is in keeping with the finding that there is an increased risk of coronary heart disease events and mortality in those with greater TSH elevations, especially greater than 10 mIU/L [21]. The same meta-analysis [14] found greater differences in the TC, LDL-C and HDL-C compared with the euthyroid group in patients with subclinical hypothyroidism when comparing those aged between 21 and 55 years of age. Regarding sex, the increases in LDL-C and decreases in HDL-C were seen regardless of the percentage of women in the group being studied.…”

“…Some studies have also conducted various subgroup analyses of effects on the lipid profile, including differences based on study location, degree of TSH elevation, age, sex, and body mass index. Examining the impact of degree of TSH elevation on lipid alterations in the recent metaanalysis [14], it was found that elevations in LDL-C, TC, and TG were greater in subgroup of patients with subclinical hypothyroidism and with TSH values greater than 10 mIU/L than in those with TSH values less than 10 mIU/ L. However, this did not apply to the degree of decrease in HDL-C values. The greater impact of higher TSH values with respect to producing a more adverse lipid profile is in keeping with the finding that there is an increased risk of coronary heart disease events and mortality in those with greater TSH elevations, especially greater than 10 mIU/L [21].…”

“…The discrepancies in the findings regarding the effects of subclinical hypothyroidism on the components of the lipid profile seen in various studies has been attributed to the heterogeneity of the populations that have been studied [13,14]. For example, in one recent study, using an initial control group of 10,827 individuals for a group of 685 participants with subclinical hypothyroidism, there were statistically significant increases in TC and LDL-C and a statistically significant decrease in HDL-C between the control group and groups with mild and more severe subclinical hypothyroidism.…”

“…A recent meta-analysis of studies on the lipid profiles of individuals with subclinical hypothyroidism accounted for population heterogeneity by including only cross-sectional studies in which those with subclinical hypothyroidism and control euthyroid participants were matched by age, sex, and body mass index. They included studies conducted before December, 2021 and identified 25 studies which contributed 3347 participants (1669 with subclinical hypothyroidism and 1688 with euthyroidism) [14]. This analysis showed that compared with the euthyroid group, individuals with subclinical hypothyroidism had significantly higher TC, LDL-C, and TG levels.…”

“…Combining the data from the various studies included in the recent meta-analysis suggests a differential effect of subclinical hypothyroidism on the different components of the lipid profile [14]. Generally, effects on the LDL-C were large size effects, whereas effects on TC, TG, and HDL-C were medium size effects.…”