Endocrine Abstracts

Objective: There is currently extensive debate regarding elevated TSH (Thyroid Stimulating Hormone) concentrations and associated cardiovascular risk. This study investigated whether correlations exists between TSH concentrations within the accepted range of normality and increasing cardiovascular risk.

Design: We performed a cross-sectional study of 728 asymptomatic women aged 45–60 years attending for thyroid screening over a twelve month period. Patients found to be biochemically hyper (TSH <0.5 (n=14)) or hypothyroid (TSH >4.5 (n=53)) were excluded. Only those patients whose TSH concentrations were found to lie within the reference range (0.5–4.5 mU/L) were included in the final analysis (n=635). Subsequently, correlations between TSH levels and risk parameters for cardiovascular disease were examined. Additionally, ten-year risk of both ischemic heart disease (IHD) and fatal cardiovascular event was calculated using Framingham risk-stratification and SCORE index calculation respectively.

Results: This study demonstrates that within the reference range, increasing TSH concentrations correlate significantly with risk parameters for the development of cardiovascular disease. Results show statistically significant correlations of increasing TSH concentrations and waist-circumference (Pearson R=0.096, P=0.017), BMI, (Pearson R=0.083, P=0.03), fasting glucose (Pearson R=0.103, P=0.01), triglycerides (Pearson R=0.136, P=0.001) and systolic blood pressure (Spearman’s R=0.081, P=0.041). However, no significant correlation with either risk of developing coronary heart disease or risk of a fatal cardiovascular event with in the next ten years was demonstrated.

Conclusion: This study demonstrates that increasing TSH concentrations within the normal reference range are associated with increased risk of cardiovascular morbidity. These findings add weight to the call for tightening of the reference range for TSH and may have clinical implications for the management of hypothyroid patients.