ketosteroid ketosteroid a ketosteroid, or an oxosteroid, is a steroid in which a hydrogen atom has been replaced with a ketone (c=o) group. steroid skeleton. carbons 18 and above can be absent. androstenedione androsterone estrone 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.