Hyperparathyroidism

Low calcium

High parathyroid hormone

Intestinal calcium absorption

Renal calcium reabsorption

Release of calcium from bones

2/3 Tonic

1/3 Pulsatile

Anabolic effect

1-Stimulate osteoblast prolif.

2-decreasing Osteoblast apoptosis.

3-New bone formation.

Tonic high levels of PTH lead to excessive release of calcium from bones and increase the risk of osteoporosis.

Binding of PTH

to

PTH receptor type 1 on osteoblasts

increases

the expression of RANK-ligand

which subsequently interacts with RANK on osteoclast precursors (Paracrine effect)

to

promote osteoclast differentiation and suppress osteoclast apoptosis.

Low

osteoprotegerin

PTH upregulates 1-alpha-hydroxylase in the kidneys