Effects of PTH on osteocyte function

Resorption Controls Bone Anabolism Driven by Parathyroid Hormone (PTH) Receptor Signaling in Osteocytes

“…Acting on cells of the osteoblastic lineage, PTH activates pathways that increase both bone resorption and formation (1,3,4). Depending on the duration and periodicity of the hormonal elevation, the balance between these two effects varies, leading to bone gain or loss on different bone envelops.…”

“…PTH down-regulates the expression of the Sost gene, which encodes the potent inhibitor of bone formation sclerostin, expressed primarily in osteocytes in bone (5,6). PTH also increases the expression of FGF23, a hormone expressed in osteocytes (and osteoblasts) that regulates phosphate reabsorption in the kidney, contributing to mineral homeostasis (4,7,8). Moreover, the major skeletal effects of PTH are recapitulated in transgenic mice expressing a constitutively active PTH receptor in osteocytes, named DMP1-8kb-caPTHR1 mice (4, 9 -11).…”

“…Earlier work demonstrates that some of actions of PTH on the skeleton are mediated by direct effects of the hormone on osteocytes, the most abundant and highly communicated cells in bone (4). PTH down-regulates the expression of the Sost gene, which encodes the potent inhibitor of bone formation sclerostin, expressed primarily in osteocytes in bone (5,6).…”

Pseudo-hypothyroidism

“…ПТГ, действуя на остеоциты, вызывает подавле-ние экспрессии OPG и повышение экспрессии RANKL, что способствует остеокластогенезу и ведет к повышению костной резорбции [10,11].…”

“…Под действием ПТГ снижается экспрессия скле-ростина, тем самым повышается остеобластогенез; кроме того ПТГ увеличивает образование и секре-цию FGF23, что сказывается на экскреции фосфора (повышается) [11].…”