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19-Norandrostenedione (4-estrene-3,17-dione, NOR) is a precursor of the anabolic steroid nandrolone. Until 2005 19-Norandrostenedione was available without prescription in United States, where it was marketed as a prohormone, but it is now classified as a Schedule III drug. It is also banned from use in many sports, including the Olympic Games, under the World Anti-Doping Code.〔(【引用サイトリンク】 title=The World Anti-Doping Code: The 2012 Prohibited List )〕 19-Norandrostenedione is readily metabolized to nandrolone after oral administration, but its potency to transactivate the androgen receptor dependent reporter gene expression is 10 times lower as compared to dihydrotestosterone (DHT). Scientific studies have shown that oral administration of 19-norandrostenedione is "a very ineffective strategy for stimulating skeletal muscle mass increases but may be associated with side effects". ''In vivo'' experiments in castrated rats demonstrated that subcutaneous treatment with 19-norandrostenedione resulted only in a stimulation of the weight of the levator ani muscle, while the prostate and seminal vesicle weights remained completely unaffected. In contrast to its metabolite nandrolone, 19-norandrostenedione highly selectively stimulates the growth of the skeletal muscles but has only weak androgenic properties.〔 In the early 2000s, contamination of androstenedione products with traces of 19-norandrostenedione caused false positives for doping tests for nandrolone because 19-norandrosterone is a metabolite of both nandrolone and 19-norandrostenedione. In a randomized controlled trial trace contamination of androstenedione with 19-norandrostenedione was sufficient for users of androstendione to test positive for nandrolone. This detail became less relevant after 19-norandrostenedione and androstenedione were banned by major sporting bodies. == See also == * selective androgen receptor modulator 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「19-Norandrostenedione」の詳細全文を読む スポンサード リンク
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