The dual role of PTH is currently understood to involve both stimulation of preosteoblast production and inhibition of preosteoblast differentiation . As a result, preosteoblast cell populations increase while osteoblast populations remain unchanged. This causes an increase in the RANKL to OPG ratio since osteoblastic cells produce more OPG and less RANKL as they mature. A short burst of PTH stimulates remodeling by increasing RANKL and suppressing OPG.