**Core Concept**
Elevated liver enzymes are often seen in conditions affecting the liver, such as cholestasis or hepatitis. These enzymes can be divided into two categories: those that are elevated in cholestasis (e.g., alkaline phosphatase, 5'-nucleotidase) and those that are not (e.g., glutamate dehydrogenase).

**Why the Correct Answer is Right**
Glutamate dehydrogenase (GLDH) is an enzyme found in the mitochondria of liver cells. It is not typically elevated in conditions affecting the liver, such as cholestasis or hepatitis. In contrast, alkaline phosphatase (ALP) and 5'-nucleotidase are both enzymes that are involved in the transport of phosphate groups across cell membranes and are often elevated in conditions where there is an obstruction to bile flow, such as in cholestasis. Gamma glutamyl transpeptidase (GGT) is another enzyme that is often elevated in conditions where there is an obstruction to bile flow. GLDH is not a specific marker for liver disease and is not typically elevated in conditions that present with icterus, pruritus, and clay-colored stools.

**Why Each Wrong Option is Incorrect**
**Option A:** Gamma glutamyl transpeptidase is often elevated in conditions where there is an obstruction to bile flow, such as in cholestasis.
**Option B:** Alkaline phosphatase is an enzyme that is involved in the transport of phosphate groups across cell membranes and is often elevated in conditions where there is an obstruction to bile flow.
**Option C:** 5'-nucleotidase is an enzyme that is involved in the breakdown of nucleotides and is often elevated in conditions where there is an obstruction to bile flow.

**Clinical Pearl / High-Yield Fact**
In a child presenting with icterus, pruritus, and clay-colored stools, it is essential to consider the possibility of biliary atresia, a condition where there is an obstruction to bile flow. Elevated liver enzymes such as alkaline phosphatase and 5'-nucleotidase can be seen in this condition.

**Correct Answer:**
✓ Correct Answer: D. Glutamate dehydrogenase