Prolactin and venous thrombosis: indications for a novel risk factor?

OBJECTIVE Several acquired risk factors for venous thrombosis (VT) are associated with high prolactin levels. Our goal was to investigate VT risk for different levels of prolactin. METHODS AND RESULTS We used data of a case-control study on leg vein thrombosis conducted between September 1999 and August 2006 at the Academic Medical Center, Amsterdam, the Netherlands. Prolactin was assessed in 187 cases (mean age, 57 years; range, 19 to 90) and 374 gender-matched controls (mean age, 57 years; range, 18 to 93). Odds ratios and 95% CI for VT risk were estimated based on several cutoff levels derived from prolactin levels in controls. Odds ratios for VT risk clearly increased with higher prolactin levels. For prolactin levels above the 75th percentile (8 μg/L), we found an odds ratio of 1.7 (95% CI 1.0 to 2.7) as compared with levels below the 50th percentile (6 μg/L). This further increased up to an odds ratio of 4.7 (95% CI 1.8 to 11.8) for prolactin levels above the 97.5th percentile (16 μg/L). The risk was most pronounced in premenopausal women. CONCLUSIONS Our data suggest that prolactin levels are associated with VT in a dose-dependent fashion. Future studies are needed to evaluate the causality of this relationship.