What best describes the primary pathophysiologic process in osteoporosis?

• A. Increased bone formation by osteoblasts
• B. Decreased bone turnover with preserved strength
• C. Excessive bone resorption by osteoclasts relative to bone formation by osteoblasts
• D. Increased calcium deposition in bone

Answer: (C)

Bone remodeling normally keeps bone mass in balance by the opposite actions of osteoclasts breaking down old bone and osteoblasts forming new bone. In osteoporosis, this balance tips toward resorption, so osteoclast activity outpaces osteoblast activity. Over time, more bone is dissolved than rebuilt, leading to reduced bone mass and a weaker bone structure with higher fracture risk. This is driven in many cases by factors like estrogen deficiency that heighten osteoclast activity.

So the essence is that excessive bone resorption by osteoclasts relative to bone formation by osteoblasts drives osteoporosis, not increased formation, not preserved strength with low turnover, and not increased calcium deposition in bone.