European Heart Journal Advance Access originally published online on November 13, 2008
European Heart Journal 2009 30(2):217-224; doi:10.1093/eurheartj/ehn508
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Are serum thyrotropin levels within the reference range associated with endothelial function?
1 Institut für Community Medicine, Ernst-Moritz-Arndt-Universität, Walther Rathenau Str. 48, D-17487 Greifswald, Germany
2 Klinik für Innere Medizin B, Ernst-Moritz-Arndt-Universität, Greifswald, Germany
3 Institut für Klinische Chemie und Laboratoriumsmedizin, Ernst-Moritz-Arndt-Universität, Greifswald, Germany
4 Franz-Volhardt-Klinik, Charité Campus Berlin-Buch, HELIOS Kliniken Berlin, Germany
Received 4 December 2007; revised 11 September 2008; accepted 23 October 2008; online publish-ahead-of-print 13 November 2008.
* Corresponding author. Tel: +49 3834 867707, Fax: +49 3834 866684, Email: voelzke{at}uni-greifswald.de
Aims: High serum thyrotropin (TSH) levels within the reference range might be associated with an increased cardiovascular risk. In the present study, we investigated the association between serum TSH levels and flow-mediated dilation (FMD) as a measure of endothelial dysfunction.
Methods and results: The study population comprised 1364 subjects (670 women) aged 25–85 years with serum TSH levels between 0.25 and 2.12 mIU/L recruited from 5-year follow-up of the Study of Health in Pomerania. No interventions were performed. Measurements of FMD and nitrate-mediated dilation (NMD) were performed in the supine position using standardized ultrasound techniques. FMD and NMD values below the median of each distribution were considered decreased. Analyses adjusted for age, sex, smoking, and systolic and diastolic blood pressure revealed a non-significant inverse trend between serum TSH levels and FMD (P = 0.130). Subjects with serum TSH levels above the highest quartile had lower median FMD values relative to subjects with serum TSH levels below the lowest quartile (4.86 vs. 5.43%, P < 0.05). A linear inverse trend between serum TSH levels and decreased FMD barely missed statistical significance (P = 0.138). Subjects with high serum TSH levels had higher odds of decreased FMD relative to subjects with low serum TSH levels (odds ratio 1.42; 95% confidence interval 1.02; 1.96; P < 0.05). These associations were more pronounced in men than in women. There were no such associations for NMD.
Conclusion: Serum TSH levels within the upper reference range are associated with impaired endothelial function. Our findings contribute to the discussion on whether the upper TSH reference limit should be redefined.
Key Words: Thyroid function • Endothelial function • Epidemiology