Wikipedia states that there are hundreds of distinct steroids found in animals, fungi, plants, and elsewhere. All natural steroids are made in living cells, either from the sterol lanosterol in animals and fungi or from cycloartenol in plants.
According to Encyclopaedia Britannica, steroids are natural or synthetic compounds with a molecular structure of seventeen carbon atoms arranged in four rings. Wikipedia.org explains that there are three cyclohexane rings and one cyclopentane ring. Steroids vary by the oxidation state of their carbon atoms and by changes to ring structure.
Encyclopaedia Britannica states that the steroid group includes all sex hormones, adrenal cortical hormones, bile acids, and sterols of vertebrates, as well as the molting hormones of insects, and many other physiologically active substances of animals and plants. Steroids have a variety of important physiological functions. Examples include promoting gestation (progesterone), aiding development of male characteristics (androgens) and facilitating proper heart function (cardiotonic steroids).
According to Saint Edwards Univerity , the sterol known as cholesterol is a precursor for steroid hormones. Cholesterol is a natural product derived from the steroid nucleus, is the building block for steroid hormones and serves as a component of their cell membrane. Steroids, fat soluble organic compounds, are a class of lipid.