Exp Clin Endocrinol Diabetes 2005; 113 - 141
DOI: 10.1055/s-2005-863000

Low serum thyrotropin is associated with high plasma fibrinogen levels. The Study of Health in Pomerania

M Dörr 1, U John 2, H Wallaschofski 3, SB Felix 1, H Völzke 2
  • 1Ernst-Moritz-Arndt-Universität, Klinik für Innere Medizin B, Greifswald
  • 2Ernst-Moritz-Arndt-Universität, Institut für Epidemiologie und Sozialmedizin, Greifswald
  • 3Ernst-Moritz-Arndt-Universität, Klinik für Innere Medizin A, Greifswald

Background: High plasma fibrinogen levels predict increased risk of cardiovascular events. Elevated vascular mortality was described for elderly people with decreased serum thyrotropin (TSH), which potentially could be attributable to alterations of the coagulation system. The aim of this analysis was to investigate the association between thyroid function and plasma fibrinogen levels.

Methods: The population-based Study of Health in Pomerania (SHIP) was performed in a previously iodine-deficient area, including 4,310 subjects aged 20 to 79 years. Data of 3,654 individuals (1734 women, 1920 men) without known thyroid disorder and with available data on plasma fibrinogen levels were analyzed. Elevated fibrinogen level was defined as a plasma concentration of more than 3.50g/l.

Results: Forty-two participants (1.1%) had elevated serum TSH, 3218 (88.1%) were euthyroid, 382 (10.5%) had decreased serum TSH and 12 (0.3%) had overt hyperthyroidism. Analysis revealed a U-shaped association between thyroid function status and plasma fibrinogen concentration. Elevated levels were observed in 11 persons with elevated serum TSH levels (26.2%), in 595 euthyroid persons (18,5%), in 114 persons with decreased serum TSH levels (29,8%), and in 4 individuals with overt hyperthyroidism (33.3%) (p<0.01). Logistic regression analysis revealed decreased TSH as an independent risk factor for elevated fibrinogen levels (odds ratio 1.57, 95%-confidence interval 1.20–2.04). Further risk factors were advanced age, increased body mass index, diabetes mellitus, current smoking, increased levels of LDL cholesterol, triglycerides and lipoprotein (a). Additionally, fibrinogen levels were associated with current usage of fibrates, vitamin k antagonists and systemic glucocorticoids.

Conclusion: There is an association between thyroid function and plasma fibrinogen levels. In particular, fibrinogen levels are elevated in subjects with decreased TSH probably explaining the association between subclinical hyperthyroidism and vascular mortality.