Which statement about alkaline phosphatase (ALP) in cholestasis is true?

• A. ALP decreases with cholestasis.
• B. ALP remains unchanged in cholestasis.
• C. ALP increases with cholestasis.
• D. ALP is only elevated in muscle injury.

Answer: (C)

Cholestasis blocks bile flow, which causes stress and injury to liver cells and biliary epithelium. In response, these cells ramp up the production and release of alkaline phosphatase into the bloodstream, so the enzyme level rises in cholestatic liver disease. While ALP also comes from bone, the hepatic/biliary source is the dominant contributor during cholestasis, often yielding a noticeable increase. That’s why ALP increasing is the correct statement. It isn’t decreasing or staying the same, and ALP is not a marker specific to muscle injury; it reflects liver/biliary and bone activity, with the liver/biliary rise being the key in cholestasis.