steroidid

Steroidid is a diverse class of organic compounds characterized by a common four-ring core structure known as the cyclopentanoperhydrophenanthrene nucleus. They occur naturally in animals, plants, and fungi and include cholesterol, steroid hormones, bile acids, and secosteroids such as vitamin D. Synthetic steroids are also widely used in medicine and industry.

Structural diversity among steroidid arises from variations in the attached side chains and functional groups, yielding broad functional categories. Major groups include sterols (such as cholesterol and bile acids), steroid hormones (glucocorticoids, mineralocorticoids, and sex hormones), and synthetic corticosteroids and anabolic agents used in therapy or research. Secosteroids, like vitamin D, are structurally related but have a partially degraded ring system.

Biosynthesis in animals centers on cholesterol, which serves as a common precursor for many steroids. The process begins with acetyl-CoA via the mevalonate pathway, with regulation by enzymes such as HMG-CoA reductase. Cholesterol produced by the liver and other tissues is the substrate for steroid hormone synthesis in mitochondria and the endoplasmic reticulum, including glucocorticoids, mineralocorticoids, and sex steroids.

Physiological roles are diverse. Cholesterol contributes to membrane structure and fluidity; steroid hormones regulate metabolism, reproduction, development, and immune function; bile acids facilitate fat digestion; and vitamin D influences calcium and phosphate homeostasis.

Medical and pharmacological use is extensive. Corticosteroids (e.g., prednisone, hydrocortisone) treat inflammation and autoimmune diseases; mineralocorticoids manage electrolyte balance; certain steroids serve in hormone replacement therapy. Abuse of anabolic steroids poses health risks, and regulatory measures monitor their non-medical use.