ABSTRACT

It has been generally accepted that cholesterol is the obligatory precursor in the biosynthesis of all steroid hormones. Details of the various steps for the synthesis of cholesterol from acetate and for its conversion to steroids were established mainly by in vitro incubation procedures using tissues such as the ovary, testis, and adrenal cortex. This chapter discusses the evidence for the steroidogenic pathway which bypasses cholesterol. It refers the alternate pathway of steroidogenesis, while that which utilizes cholesterol as an obligatory intermediate will be termed the classical pathway of steroidogenesis. The chapter discusses the classical pathway of biosynthesis and metabolism of steroid hormones, and reviews its salient features to facilitate comparison with the alternate pathway. It presents the metabolism and biological action of the ring B unsaturated estrogens.