The parent substance in the biosynthesis of androgens and estrogens is

• A. Cholesterol
• B. Cortisol
• C. Catecholamines
• D. Progesterone

Answer: (A)

Cholesterol is the starting material for all steroid hormones. In steroid biosynthesis, cholesterol is transported into mitochondria and cleaved by cholesterol side-chain cleavage to form pregnenolone, the immediate precursor to all steroid hormones. From there, pathways branch to produce androgens and estrogens through specific enzymes, with aromatase converting androgens to estrogens. Cortisol and progesterone are also products in this shared pathway, but they are downstream relatives, not the universal parent. Catecholamines, by contrast, come from tyrosine and are not steroids. Thus cholesterol is the parent substance for the biosynthesis of androgens and estrogens.