Rethinking Normal Thyroid-Stimulating Hormone (TSH): Stroke Risk and Metabolic Implications in High-Risk...

Area of Science:

• Endocrinology
• Cardiovascular Medicine
• Clinical Research

Background:

• Thyroid-stimulating hormone (TSH) levels within the normal range are often considered clinically insignificant for cardiovascular outcomes.
• However, subtle variations in normal TSH may influence cardiovascular risk, particularly in high-risk populations.

Purpose of the Study:

• To investigate the association between normal-range TSH variations and cardiovascular outcomes in euthyroid patients with hypertension and dyslipidemia.
• To determine if lower-normal or upper-normal TSH levels correlate with specific cardiovascular risk factors or events.

Main Methods:

• A cross-sectional study of 463 middle-aged euthyroid patients (hypertension, dyslipidemia) with TSH levels between 0.5-5.2 mIU/L.
• Patients were stratified into TSH tertiles (lower: 0.5-1.3, middle: >1.3-2.16, upper: >2.16-5.2 mIU/L) and compared.
• Statistical analyses included correlation, regression, and comparison between TSH ≤2.16 mIU/L and TSH >2.16 mIU/L groups.

Main Results:

• Higher triglycerides and Tg-to-HDL ratio were observed in the upper-normal TSH group (p<0.05).
• TSH positively correlated with BMI and Tg-to-HDL ratio.
• Stroke prevalence was significantly higher in the lower-normal TSH range (6.1% vs. 2.0%, p=0.047).
• Multivariate regression indicated lower-normal TSH was associated with a five-fold increased stroke likelihood (OR: 5.08, p=0.031).

Conclusions:

• Within the normal TSH range, lower levels are associated with an increased risk of stroke in high-risk patients.
• Upper-normal TSH levels correlate with adverse lipid profiles and markers of insulin resistance.
• These findings emphasize the clinical relevance of evaluating TSH levels even within the normal range for cardiovascular risk assessment.