The influence of hormonal contraceptives on sex hormone binding globulin (SHBG) capacity

The sex hormone binding globulin (SHBG) capacity was measured by ammonium sulfate precipitation in the plasma of women using various progestational steroids and combined hormonal contraceptives. For reference purposes, determinations were done in the plasma of normal males, normal menstruating women, women at different stages of pregnancy, post-menopausal women, and women using ethinylestradiol (EE2) 0.050 mg daily. The progestational compounds, d-norgestrel (0.030 mg daily), lynestrenol (0.5 mg daily), and medroxyprogesterone acetate (150 mg three-monthly intramuscularly), caused a decrease of about 30% below the level found in normal menstruating women. With lynestrenol 5 mg daily, a further decrease of SHBG was observed. EE2 (0.050 mg daily) alone increased SHBG. This effect of EE2 was (partly) neutralized by its combination with d-norgestrel or lynestrenol. The combination of EE2 with megestrol acetate gave rise to high SHBG capacity values, comparable to those attained during pregnancy. The response of SHBG to the use of hormonal contraceptives is different from that of transcortin-binding capacity as found by other authors