What substance is the precursor to all steroid hormones?

What substance is the precursor to all steroid hormones?

• A. Fatty acid
• B. Cholesterol
• C. Triglyceride
• D. Phospholipid

Answer: (B)

Cholesterol is the starting material for all steroid hormones. The biosynthetic pathway begins with cholesterol, which is converted by the enzyme CYP11A1 in the mitochondria to pregnenolone—the common precursor for glucocorticoids, mineralocorticoids, and the sex steroids. From pregnenolone, a series of enzymatic steps produce hormones such as cortisol, aldosterone, testosterone, estradiol, and progesterone. These steroids are lipophilic and act by binding intracellular receptors to regulate gene expression. The other lipids listed—fatty acids, triglycerides, and phospholipids—do not form the steroid backbone, so they are not precursors to steroid hormones.

Cholesterol is the starting material for all steroid hormones. The biosynthetic pathway begins with cholesterol, which is converted by the enzyme CYP11A1 in the mitochondria to pregnenolone—the common precursor for glucocorticoids, mineralocorticoids, and the sex steroids. From pregnenolone, a series of enzymatic steps produce hormones such as cortisol, aldosterone, testosterone, estradiol, and progesterone. These steroids are lipophilic and act by binding intracellular receptors to regulate gene expression. The other lipids listed—fatty acids, triglycerides, and phospholipids—do not form the steroid backbone, so they are not precursors to steroid hormones.