How does the relative activity of osteoblasts and osteoclasts change from childhood into older adulthood, and what is the primary consequence for bone mass?

Osteoclasts dominate in childhood to shape bones during growth while osteoblasts take over in adulthood to maintain bone mineral homeostasis, resulting in higher bone mass after age 30.

The relative activities oscillate monthly according to dietary calcium intake with no long-term trend, so aging per se does not change net bone balance unless calcium intake is below 100 mg/day.

Osteoblast activity dominates throughout life while osteoclast activity is negligible after puberty, so adult bone mass remains virtually unchanged except with traumatic injury.

In childhood and up to about the third decade osteoblast deposition exceeds osteoclast resorption causing net gains in bone mass; from mid-adulthood onward resorption often exceeds deposition leading to progressive bone loss.