[Progestagens in contraception].

The different spectrum of biological actions of the various synthetic progestogens is compared on the basis of their chemical structure, pharmacokinetics and interaction with the multiple receptors. In detail, the mechanism of action of the progesterone derivatives (medroxyprogesterone acetate, chlormadinone acetate and cyproterone acetate), the norethisterone-related (norethisterone, ethynodiol diacetate, lynestrenol and norethynodrel) and the norgestrel-related progestogens (levonorgestrel, desogestrel, gestodene and norgestimate), and a possible influence of some metabolites upon the biological profile are discussed. With regard to the progestogenic activity, the time-course of the serum concentrations of the steroids after the application (pharmacokinetics) which is dependent upon absorption, metabolization in the gastro-intestinal tract and liver (first-pass effect), distribution and storage in fat and other tissues, binding to serum proteins, inactivation, and conjugation, is of particular importance. The various side-effects of the progestogens are mainly based on their influence upon hepatic metabolism (lipids, lipoproteins, serum proteins) and upon other organs which is dependent on their different estrogenic, antiestrogenic, androgenic, antiandrogenic, glucocorticoid and antimineralocorticoid actions.