An examination of the relationship between normal range thyrotropin and cardiovascular risk parameters: a study in healthy women.

Objective: To investigate the relationship between thyrotropin concentrations within the accepted reference range and cardiovascular risk.

Design: Initially, 728 women aged 45-60 years were enrolled over a 12-month period. All participants underwent full cardiovascular assessment, including detailed health questionnaire, sphygomanometry, body mass index (BMI) calculation, fasting glucose and lipid profiling, and measurement of serum thyrotropin concentrations. Patients whose thyrotropin concentrations were within the reference range (0.5-4.5 mU/L) were divided into quartiles (n = 629). The means of cardiovascular risk parameters between the first (n = 158) and fourth (n = 157) quartile were compared. Subsequently, the relationships between thyrotropin concentration and risk parameters for cardiovascular disease were examined.

Main Outcome: This study demonstrates that, within the reference range, increasing thyrotropin concentrations are associated with increasing risk parameters for the development of cardiovascular disease. Subjects with thyrotropin concentrations within the uppermost quartile of the reference range had significantly increased waist circumference, BMI, glucose, triglyceride, and systolic blood pressure measurements when compared to those in the lowermost quartile. Furthermore, significant relationships between thyrotropin and waist circumference, BMI, and fasting glucose and triglycerides concentrations were demonstrated. Finally, independent relationships between thyrotropin and both fasting glucose and triglyceride concentrations were demonstrated.

Conclusion: Within the reference range, increasing thyrotropin concentrations are associated with increasing cardiovascular risk parameters. Fasting glucose and triglycerides have been shown to be independently associated with thyrotropin concentration.