Heparin cofactor Ii levels are increased by the use of combined oral contraceptives
Mackie, I.J.; Segal, H.; Burren, T.; Gallimore, M.; Walshe, K.J.; Robinson, G.; Machin, S.J.
Blood Coagulation and Fibrinolysis An International Journal in Haemostasis and Thrombosis 1(6): 647-651
1990
ISSN/ISBN: 0957-5235 PMID: 2133244 Document Number: 351778
Heparin cofactor II, a less well characterized heparin-dependent antithrombin factor than antithrombin III, was determined in 11 women before, during and after a 6 month trial of oral contraceptives, in 16 women aged 18-60, in 16 men aged 22-55, in 5 patients with known antithrombin III deficiency, and in a series of 16 patients in a critical care unit. The oral contraceptives used in the trial were Femodene (Schering, Burgess, Hill, U.K.) in 6 women and Marvelon (Organon, Cambridge, U.K.) in 5. The assay was an amidolytic microtiter method standardized against normal human serum. The assay was linear up to 1.5 U/ml, and HCII was not lost by repeated freezing and thawing. HCII levels were normal in patients with AT III deficiency, but ranged from 0.10-1.11 in intensive care patients. In normal subjects the mean HCII levels were 1.07 U/ml, and were significantly higher for women, 1.16, than for men, 0.97 U/ml. During intake of oral contraceptives, HCII rose significantly from 0.86 u/ml to 1.10 at cycle 1, 1.08 at cycle 3, and 1.19 at cycle 6. 2 weeks after stopping pills, the mean HCII level fell to 1.03. In contrast, AT III declined during pill cycles.