If ALP is elevated with a normal GGT, what is the most likely tissue source?

• A. Liver
• B. Intestine
• C. Bone
• D. Kidney

Answer: (C)

When trying to identify the source of an elevated alkaline phosphatase (ALP), it's helpful to know that ALP comes in several tissue-specific forms (bone, liver, intestine, placenta). Gamma-glutamyl transferase (GGT) is a liver-associated enzyme that rises with hepatobiliary disease. So, if ALP is high but GGT remains normal, the elevation is likely from a nonhepatic source. Among the tissues listed, bone is the classic nonhepatic source of ALP, reflecting osteoblastic activity during growth, fracture healing, or bone turnover. That makes bone the most likely tissue source in this scenario. The liver would typically elevate GGT together with ALP in hepatobiliary problems, and while intestinal ALP can contribute, bone is the common nonhepatic culprit in isolated ALP elevations with normal GGT.