Steroid production in the adrenal cortex is a function of which organelle?

• A. Nucleus
• B. Rough endoplasmic reticulum
• C. Smooth endoplasmic reticulum
• D. Golgi apparatus

Answer: (C)

Steroid hormones are made by enzymes that reside in the smooth endoplasmic reticulum of steroidogenic cells in the adrenal cortex. While the initial cholesterol-to-pregnenolone step begins in the mitochondria, the subsequent enzymatic conversions that produce glucocorticoids, mineralocorticoids, and androgens mostly occur in the smooth ER, which houses the cytochrome P450 enzymes essential for these reactions. This makes the smooth ER the primary site for steroid production in the adrenal cortex.

Nucleus contains genetic material for transcription, rough endoplasmic reticulum handles protein synthesis, and the Golgi apparatus processes and packages proteins for secretion—roles not suited to producing lipid-soluble steroids.