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Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Steroid synthesis occurs via normal steroid biosynthetic pathways.

Within Leydig cells, testosterone is produced mainly by the pathway:

  • cholesterol
  • pregnenolone
  • 17-alpha-hydroxypregnenolone
  • dehydroepiandrosterone
  • andrestenediol
  • testosterone

Testosterone may then be converted into oestradiol-17beta by:

  • Sertoli cells
  • peripheral adipose tissue containing the enzyme aromatase; particularly relevant in obese men where feminization can occur

Alternatively, the peripheral target tissue which testosterone acts upon may contain a 5-alpha-reductase enzyme. This converts testosterone to 5-alpha-dihydrotestosterone.

The adrenal cortex, ovarian follicles and ovarian stromal cells tends to produce androstenedione as its main androgen. It is derived from:

  • dehydroepiandrosterone, produced by the pathway detailed above
  • progesterone via 17-alpha-hydroxyprogesterone

Synthetic modification of the basic androgen structure - removal of the methyl group at C19 - minimizes virilizing effects while maximizing stimulation of skeletal muscle. This is the basis of anabolic steroids.

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