Cardiovascular Risk Assessment in Subclinical Hypothyroid Individuals with Thyroid-stimulating Hormone <10 uIU/ml

Subclinical hypothyroidism is defined as a serum thyroid-stimulating hormone (TSH) level above the upper limit of normal despite normal levels of serum free thyroid hormones. While the cardiovascular risk in overt hypothyroidism is well established, the risk in subclinical hypothyroidism, especially those with TSH <10 uIU/ml, is not clear. Here, we aimed to study the cardiovascular risk among subclinical hypothyroid individuals with TSH <10 uIU/ml by using epicardial fat thickness (EFT) measurement.

This was a cross-sectional study conducted over 19 months. In this study, we included 35 cases of subclinical hypothyroidism who had a TSH <10 uIU/ml and 35 age- and sex-matched controls. A single expert cardiologist did EFT assessment for all the cases and controls.

The median (25^th-75^th percentile) EFT was significantly higher in cases (3.8 [2.85-4.775] mm) compared to controls (2.6 [2-3.55]mm, P = 0.0002). A significant, moderately positive correlation was seen between TSH and EFT, with a correlation coefficient of 0.561. Subgroup analysis showed that the median EFT was significantly higher in the ≥7.6 to <10 uIU/ml TSH group (4.4 [3.825-5] mm) compared to the >5.33 to <7.6 uIU/ml group (2.8 [2.2-3.5] mm, P = 0.002). LDL and TSH were associated with high EFT (>4 mm). The receiver operating characteristic curve analysis showed that the discriminatory power of TSH (AUC 0.741; 95% confidence interval [CI]: 0.577 to 0.906) and LDL (AUC 0.752; 95% CI: 0.580 to 0.924) were acceptable to predict EFT >4 mm.

Individuals with SCH exhibited significantly higher EFT compared to euthyroid controls, with a positive correlation observed between TSH levels and EFT.