[Molecular structure and drug activity. Example: sex hormones].

In sexual-hormone activity differences arise when only a minimum change in the structure of a known molecule is made. Even the physiological hormones have similar structures but extremely different properties. Small variations of the steroid molecule lead to orally active progestogens and estrogens. The discovery of orally active androgens and the development of anabolic agents and antiandrogens proceeds also by very small changes of known structures. Out of a million possible variations of the steroid molecule, the synthesis of approximately 80 000 structures has been realized.