Relationship of Estrogen and Vitamin K.∗

Summary Estradiol injection into male rats kept on a Vit. K-free diet was effective in lowering plasma prothrombin time to normal values in 6 hours. This Vit. K-like activity was observed even at a dosage of 20 μg/rat. Conversely, testosterone administration (1 mg/rat) to female rats significantly increased plasma prothrombin time as compared to untreated controls. In contrast to the results observed with rats, male and female chicks were equally susceptible to dietary Vit. K deficiency, and estradiol administration, even at a dose of 1 mg/chick, did not alleviate the hypoprothrombinemia.