Norpregnenes are a class of steroids that are produced by the metabolism of progesterone and other pregnanes. They are characterized by the absence of a double bond between carbons 4 and 5, and the presence of a ketone group at carbon 3. Some examples of norpregnenes include dehydroepiandrosterone (DHEA), androstenedione, and pregnenolone. These steroids are important intermediates in the biosynthesis of various hormones, including cortisol, aldosterone, androgens, and estrogens. They play a role in various physiological processes such as sexual development, immune function, and stress response.