@mkoch
rebound effect seems more accurate.

Prolia (denosumab) withdrawal, or discontinuation, causes a rapid loss of bone density and a high risk of "rebound" fractures, particularly multiple vertebral (spine) fractures. When stopped, the protective effect disappears, and bone turnover increases significantly within months. It is crucial to transition to another osteoporosis medication.

Prolia (denosumab) withdrawal is a "rebound phenomenon" occurring when stopping the injection, characterized by a rapid surge in bone-resorbing cells (osteoclasts). This causes accelerated bone density loss and a high risk of multiple vertebral fractures, often within 6–12 months of missing a dose.

It is believed that Prolia stops the osteoclasts but the osteoclasts or preosterclasts don't go away they just "dam" up and then release in a surge when Prolia is stopped.

" Prolia inhibits a protein called RANKL, which is essential for the formation and survival of osteoclasts (cells that break down bone). Recent studies have revealed that during treatment, osteoclasts do not simply disappear; instead, they can split into smaller, dormant pieces called osteomorphs that "hide" in the bone.
The "Surge" Upon Stopping: Once Prolia leaves the body—typically about six to nine months after the last injection—these osteomorphs can rapidly reassemble into active osteoclasts. This leads to a sudden and massive increase in bone resorption (breakdown), often reaching levels higher than before treatment began.
Rapid Bone Loss: Because these cells are no longer inhibited, they can quickly dissolve the bone density gains made during treatment. Many patients lose all their bone density improvements within 12 to 24 months of stopping.
Rebound Fracture Risk: This surge in bone breakdown significantly increases the risk of multiple vertebral fractures (spine fractures), which can occur as early as seven months after the last dose."