In primary hyperparathyroidism I know there is an increase in calcium and a decrease in phosphorus. The calcium is taken from the bones so that's why...

In primary hyperparathyroidism I know there is an increase in calcium and a decrease in phosphorus. The calcium is taken from the bones so that's why there is an increase in Ca. So does this mean that there is an increase osteoclastic activity? I don't really understand what "osteoclastic activity" means??? I looked it up and it gave me a definition for osteoclasis but I'm not sure that's the same thing.... can you help with what this means?