Abstract

The binding of different synthetic steroids, used in hormonal contraception, to Sex Hormone Binding Globulin (SHBG)was studied by measuring their ability to displace tritiated testosterone from SHBG in a competitive protein binding system. Only 19-nortestosterone derivates had any significant ability to displace testosterone from SHBG, dnorgestrel (d-Ng) being the strongest displacer. Increasing the SHBG levels in women with previous constant plasma d-Ng levels increased these levels two-to sixfold. It is concluded that SHBG is the main carrier protein for d-Ng. The strong testosterone displacing activity of d-Ng might also explain androgenic side effects observed with d-Ng containing oral contraceptives.

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