Which of the following is NOT a known function of hepatocytes?

• A. Synthesis of cholesterol
• B. Secretion of bile
• C. Protein storage
• D. Vitamin D synthesis

Answer: (D)

Hepatocytes are busy producers and processors: they synthesize cholesterol, they generate bile and secrete it into the bile ducts, and they make a wide array of plasma proteins. They don’t actually synthesize vitamin D. In the body, vitamin D is produced in the skin and then activated through metabolism in the liver and kidneys; the liver’s role is to hydroxylate vitamin D to 25-hydroxyvitamin D, not to synthesize vitamin D itself. So the statement that vitamin D synthesis is a function of hepatocytes isn’t accurate. The other options describe real hepatocyte activities: cholesterol synthesis is a classic liver function, and bile secretion is a primary liver duty. Protein storage isn’t a main role of hepatocytes, since the liver primarily synthesizes and releases proteins (like albumin and clotting factors) rather than storing them as a major function.