ABSTRACT
The biosynthesis of steroid hormones is the result of sequential hydroxylation and isomerization reactions which convert cholesterol to the physiologically active mineralocorticoids, glucocorticoids, androgens and oestrogens. The major sites of steroidogenesis are the ovaries, testes, adrenal glands and placenta although other organs such as the brain, liver and adipose tissue can play a significant role. A number of factors determine whether a steroid molecule will remain on the single active site of CYP17 and undergo cleavage of the 17,20 bond to produce androgens. Cholesterol can be synthesized from acetate in all steroidogenic tissues but the favoured route is to obtain the steroid from dietary sources via low density lipoprotein. The mechanism by which steroidogenesis is limited to a small number of tissues is not understood. The first line of tissue specificity must be the presence or absence of receptors for the various trophic hormones.
