Androgenicity

NaturaHy occurring and synthetic estrogens and androgens have been extensively and safely used to improve efficiency and carcass composition ia growing beef catde in the United States since the early 1950s. Several anaboHc steroid implants have been approved for use in beef catde in the United States, but only one, zeranol [55331-29-8] is approved for use in lambs. Anabolic steroids are not used for growth regulation in swine or poultry (see Steroids). 

Classification of the anabolic steroids is based on chemical stmctures and associated actions. A review of the biosynthesis and metabolism of the naturally occurring estrogens and androgens is available (1). Names, descriptions, approval dates, and recommended doses of the commercial products are found in References 1, 8, and 9. Although steroids may be orally active, the FDA approved mode of adrninistration is the subcutaneous implant. Effective dose is lower with implant rather than oral adrninistration. 

Extracts of corpora lutea were known ia the early tweatieth ceatury to inhibit ovulatioa ia animals. Pure progesterone (3), the active component of the extracts, was isolated ia 1934 and its stmcture reported (15). Several problems limited its use and drove efforts to develop progesterone analogues, ie, it was available only ia small quantities from animal sources, was not orally active, and was discovered to cause androgenic side effects. 

Steroid Hormones and Neurosteroids. Steroids (qv) can affect neuroendocrine function, stress responses, and behavioral sexual dimorphism (78,79) (see Steroids). Mineralocorticoid, glucocorticoid, androgen, estrogen, and progesterone receptors are localized in the brain and spinal cord. In addition to genomic actions, the neurosteroid can act more acutely to modulate the actions of other receptors or ion channels (80). Pregnenolone [145-13-17, ( ) dehydroepiandosterone [53-43-0] C H2 02 (319) are excitatory neurosteroids found in rat brain, independent of adrenal... 

Hormonal effects on the aging process have been areas of current interest. The intricacies of the interaction of the various hormones are undoubtedly involved in the aging process and hence these hormones could be called antiaging agents. Both androgens and estrogens have been studied. Low level estrogen replacement therapy (ERT) has been used to treat postmenopausal women. 

Steroid hormones can be subdivided into sex hormones (androgens, estrogens, and progestins) and corticosteroids (glucocorticoids and mineralocorticoids). 

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