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Δ4-Androstenedione (abbreviated as Δ4-dione), commonly referred to simply as androstenedione, and also known as androst-4-ene-3,17-dione or 17-ketotestosterone, is an endogenous androgen steroid hormone and intermediate in the biosynthesis of testosterone from dehydroepiandrosterone (DHEA). In turn, Δ4-dione is also a precursor of dihydrotestosterone (DHT), estrogens such as estradiol and estrone, and the neurosteroid 3α-androstanediol. ==Biosynthesis== Δ4-Dione is the common precursor of the androgen and estrogen sex hormones. Δ4-Dione can be biosynthesized in one of two ways. The primary pathway involves conversion of 17-hydroxypregnenolone to DHEA by way of 17,20-lyase, with subsequent conversion of DHEA to Δ4-dione via the enzyme 3β-hydroxysteroid dehydrogenase. The secondary pathway involves conversion of 17-hydroxyprogesterone, most often a precursor to cortisol, to Δ4-dione directly by way of 17,20-lyase. Thus, 17,20-lyase is required for the synthesis of Δ4-dione, whether immediately or one step removed. Δ4-Dione is produced in the adrenal glands and the gonads. The production of adrenal Δ4-dione is governed by adrenocorticotrophic hormone (ACTH), whereas production of gonadal Δ4-dione is under control by the gonadotropins. In premenopausal women, the adrenal glands and ovaries each produce about half of the total Δ4-dione (about 3 mg/day). After menopause, Δ4-dione production is about halved, due primarily to the reduction of the steroid secreted by the ovary. Nevertheless, Δ4-dione is the principal steroid produced by the postmenopausal ovary. Some Δ4-dione is also secreted into the plasma, and may be converted in peripheral tissues to testosterone and estrogens. 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「4-Androstenedione」の詳細全文を読む スポンサード リンク
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