Indicators of bone formation includes all of following except
**Core Concept**
Bone formation is a complex process involving the coordinated action of various cells and biochemical markers. The process of bone formation involves the activity of osteoblasts, which are responsible for the synthesis of the organic bone matrix, and the subsequent mineralization of this matrix by osteoblasts and osteocytes.
**Why the Correct Answer is Right**
The correct answer is a marker that is associated with bone resorption, not bone formation. Bone resorption is a process mediated by osteoclasts, which break down the bone matrix and release various biochemical markers into the circulation. These markers can be used to assess the rate of bone resorption and guide treatment decisions in conditions such as osteoporosis.
**Why Each Wrong Option is Incorrect**
* **Option A:** Osteocalcin is a marker of bone formation and is produced by osteoblasts. It is involved in the mineralization of the bone matrix and is often used as a marker of bone formation.
* **Option B:** Bone-specific alkaline phosphatase (BSAP) is an enzyme produced by osteoblasts and is involved in the mineralization of the bone matrix. It is often used as a marker of bone formation.
* **Option C:** Procollagen type I N-terminal propeptide (PINP) is a marker of bone formation and is produced by osteoblasts. It is involved in the synthesis of the collagen matrix and is often used as a marker of bone formation.
**Clinical Pearl / High-Yield Fact**
Osteocalcin and BSAP are often used together as markers of bone formation, as they provide complementary information about the process of bone mineralization.
**Correct Answer:** D.