RELATION BETWEEN SEX HORMONE BINDING GLOBULIN AND D-NORGESTREL LEVELS IN PLASMA

Abstract

In order to investigate the effect of changes in sex hormone binding globulin (SHBG) levels on d-norgestrel (d-Ng) levels in plasma, plasma levels of SHBG and d-Ng were studied during 1 treatment cycle in 6 women on oral contraceptives containing d-Ng and ethinylestradiol (EOe2) and in 3 women using s.c. silastic rods containing d-Ng concomitantly taking EOe2 for 3 wk. A significant positive correlation between SHBG and d-Ng levels was found in 7 of 9 subjects studied. Evidence is provided for an in vivo binding of d-Ng to SHBG, a SHBG influence on the metabolic clearance rate of d-Ng and consequently a dependence of the plasma levels of d-Ng on SHBG concentrations in the plasma. The concept is supported that the clinically and biochemically observed anti-estrogenic/androgenic effects observed in women on d-Ng containing medication are due to a displacement of testosterone from SHBG by d-Ng. [This displacement of testosterone could explain androgenic side-effects which are encountered in women on oral contraceptives containing d-Ng.].