Estrogen Therapy Induced Antithrombin III Decrease And Deficiency In Patients With Prostatic Cancer

Plasma AT III activity was studied in 12 patients with cancer of the prostate receiving estrogen therapy in different dosages. AT III was determined with an automated chromogenic method (normal value 0.80-1.40 u/ml). In six patients with maintenance diethylstil- bestrol (DES) therapy(2.5 mg/48 hrs) mean plasma AT III activity was normal (X 0.88 u/ml, range 0.74-1.05 u/ml). The dose of DES at 15 mg. daily resulted in a marked AT III activity decrease (mean 0.24 u/ml) in all six patients. In patients with low normal initial plasma AT III activity acquired AT III deficiency, with enhanced risk of thromboembolic complications, may develop. The observations suggest that plasma AT III activity should be monitored before and during estrogen therapy in prostatic cancer patients. In patients with acquired AT III deficiency ( <0.80 u/ml) prophylactic administration of low dose heparin subcutaneously should be considered.