Summary
Low testosterone levels in men have been associated with cardiovascular risk factors,
some prothrombotic factors, and lately also an increased risk of both cardiovascular
disease and all-cause mortality. Experimental studies have shown increased synthesis
and release of tissue factor pathway inhibitor (TFPI) by physiological levels of testosterone
in endothelial cells. Our hypothesis was that elderly men with low testosterone levels
would have lower plasma levels of plasma free TFPI with subsequent increased thrombin
generation. Elderly men with low (n=37) and normal (n=41) testosterone levels were
recruited from a general population, and tissue factor (TF)-induced thrombin generation
ex vivo and plasma free TFPI Ag were measured. Elderly men with low testosterone levels had
lower plasma free TFPI Ag (10.9 ± 2.3 ng/ml vs. 12.3 ± 3.0 ng/ml, p=0.027) and shorter
initiation phase of TF-induced coagulation assessed by lag-time (5.1 ± 1.0 min vs.
5.7 ± 1.3, p=0.039). The differences between groups remained significant and were
strengthened after adjustment for waist circumference and other cardiovascular risk
factors. Lag-time increased linearly across quartiles of plasma free TFPI Ag (p<0.001).
Multiple regression analysis revealed that total and free testosterone were independent
predictors of plasma free TFPI Ag. Our findings suggest that low testosterone levels
in elderly men is associated with low plasma free TFPI Ag and subsequent shortened
initiation phase of TF-induced coagulation.
Keywords
Men - testosterone - TFPI - thrombin generation