synthesis
Last reviewed 01/2018
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.