Systemic hormonal control exerts its effect through the regulation of local target tissues,
which in turn regulate upstream signals in a feedback loop. The parathyroid hormone (PTH)
axis is a well defined hormonal signaling system that regulates calcium levels and bone
metabolism. To understand the interplay between systemic and local signaling in bone, we
examined the effects of deficiency of the bone matrix protein osteopontin (OPN) on the
systemic effects of PTH specifically within osteoblastic cell lineages. Parathyroid hormone …