Pregnenediones are a class of steroid hormones that contain a pregnane structure, which is a skeleton formed by four fused cyclohexane rings. Specifically, pregnenediones are characterized by having a ketone group (a carbonyl group, -C=O) at the 20th carbon position of this pregnane structure. They can be further classified into various subgroups based on the presence and location of other functional groups in the molecule.

Pregnenediones are not typically used as medications, but they do play important roles in the human body. For example, progesterone is a naturally occurring pregnenedione that plays a crucial role in maintaining pregnancy and preparing the uterus for childbirth. Other pregnenediones may also have hormonal activity or serve as intermediates in the synthesis of other steroid hormones.