A ketosteroid, or an oxosteroid, is a steroid in which a hydrogen atom has been replaced with a ketone (C=O) group. A 17-ketosteroid is a ketosteroid in which the ketone is located specifically at the C17 position (in the upper right corner of most structure diagrams). Examples of 17-ketosteroids include: Androstenedione Androstanedione Androsterone Dehydroepiandrosterone Epiandrosterone Epietiocholanolone Etiocholanolone 17-Ketosteroids are endogenous steroid hormones. See also Hydroxysteroid Hydroxysteroid dehydrogenase External links Ketones Steroids