Bone resorption

Bone Resorption
Bone Resorption
	Light micrograph of an osteoclast displaying typical distinguishing characteristics: a large cell with multiple nuclei and a "foamy" cytosol.
Specialty	Rheumatology

Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break down the tissue in bones^[1] and release the minerals, resulting in a transfer of calcium from bone tissue to the blood.^[2]

The osteoclasts are multi-nucleated cells that contain numerous mitochondria and lysosomes. These are the cells responsible for the resorption of bone. Osteoblasts are generally present on the outer layer of bone, just beneath the periosteum. Attachment of the osteoclast to the osteon begins the process. The osteoclast then induces an infolding of its cell membrane and secretes collagenase and other enzymes important in the resorption process. High levels of calcium, magnesium, phosphate and products of collagen will be released into the extracellular fluid as the osteoclasts tunnel into the mineralized bone. Osteoclasts are prominent in the tissue destruction found in psoriatic arthritis and rheumatological disorders.^[3]

The human body is in a constant state of bone remodeling.^[4] Bone remodeling is a process which maintains bone strength and ion homeostasis by replacing discrete parts of old bone with newly synthesized packets of proteinaceous matrix.^[5] Bone is resorbed by osteoclasts, and is deposited by osteoblasts in a process called ossification.^[6] Osteocyte activity plays a key role in this process. Conditions that result in a decrease in bone mass can either be caused by an increase in resorption or by a decrease in ossification. During childhood, bone formation exceeds resorption. As the aging process occurs, resorption exceeds formation.^[5]

Bone resorption rates are much higher in post-menopausal older women due to estrogen deficiency related with menopause.^[7] Common treatments include drugs that increase bone mineral density. Bisphosphonates, RANKL inhibitors, SERMs—selective oestrogen receptor modulators, hormone replacement therapy and calcitonin are some of the common treatments.^[8] Light weight bearing exercise tends to eliminate the negative effects of bone resorption.^[9]

^ Bone+Resorption at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
^ Teitelbaum SL (September 2000). "Bone resorption by osteoclasts". Science. 289 (5484): 1504–1508. Bibcode:2000Sci...289.1504T. doi:10.1126/science.289.5484.1504. PMID 10968780.
^ Mensah KA, Schwarz EM, Ritchlin CT (August 2008). "Altered bone remodeling in psoriatic arthritis". Current Rheumatology Reports. 10 (4): 311–317. doi:10.1007/s11926-008-0050-5. PMC 2656567. PMID 18662512.
^ Hall JE, Guyton AC (2011). Guyton and Hall textbook of medical physiology (12th ed.). Philadelphia, Pa: Saunders, Elsevier. ISBN 978-1-4160-4574-8.
^ ^a ^b Clarke B (November 2008). "Normal bone anatomy and physiology". Clinical Journal of the American Society of Nephrology. 3 (Suppl 3): S131–S139. doi:10.2215/CJN.04151206. PMC 3152283. PMID 18988698.
^ Cite error: The named reference pmid21689804 was invoked but never defined (see the help page).
^ Feng X, McDonald JM (2011-01-01). "Disorders of bone remodeling". Annual Review of Pathology. 6: 121–145. doi:10.1146/annurev-pathol-011110-130203. PMC 3571087. PMID 20936937.
^ Russell G, Mueller G, Shipman C, Croucher P (2001-01-01). "Clinical Disorders of Bone Resorption". The Molecular Basis of Skeletogenesis. Novartis Foundation Symposia. Vol. 232. pp. 251–267, discussion 267–271. doi:10.1002/0470846658.ch17. ISBN 9780471494331. PMID 11277085. {{cite book}}: |journal= ignored (help)
^ Shanb AA, Youssef EF (September 2014). "The impact of adding weight-bearing exercise versus nonweight bearing programs to the medical treatment of elderly patients with osteoporosis". Journal of Family & Community Medicine. 21 (3): 176–181. doi:10.4103/2230-8229.142972. PMC 4214007. PMID 25374469.

[1] Bone+Resorption at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

[Teitelbaum_SL.-2] Teitelbaum SL (September 2000). "Bone resorption by osteoclasts". Science. 289 (5484): 1504–1508. Bibcode:2000Sci...289.1504T. doi:10.1126/science.289.5484.1504. PMID 10968780.

[3] Mensah KA, Schwarz EM, Ritchlin CT (August 2008). "Altered bone remodeling in psoriatic arthritis". Current Rheumatology Reports. 10 (4): 311–317. doi:10.1007/s11926-008-0050-5. PMC 2656567. PMID 18662512.

[ReferenceA-4] Hall JE, Guyton AC (2011). Guyton and Hall textbook of medical physiology (12th ed.). Philadelphia, Pa: Saunders, Elsevier. ISBN 978-1-4160-4574-8.

[Clarke_2008-5] Clarke B (November 2008). "Normal bone anatomy and physiology". Clinical Journal of the American Society of Nephrology. 3 (Suppl 3): S131–S139. doi:10.2215/CJN.04151206. PMC 3152283. PMID 18988698.

[pmid21689804-6] Cite error: The named reference pmid21689804 was invoked but never defined (see the help page).

[7] Feng X, McDonald JM (2011-01-01). "Disorders of bone remodeling". Annual Review of Pathology. 6: 121–145. doi:10.1146/annurev-pathol-011110-130203. PMC 3571087. PMID 20936937.

[8] Russell G, Mueller G, Shipman C, Croucher P (2001-01-01). "Clinical Disorders of Bone Resorption". The Molecular Basis of Skeletogenesis. Novartis Foundation Symposia. Vol. 232. pp. 251–267, discussion 267–271. doi:10.1002/0470846658.ch17. ISBN 9780471494331. PMID 11277085. {{cite book}}: |journal= ignored (help)

[9] Shanb AA, Youssef EF (September 2014). "The impact of adding weight-bearing exercise versus nonweight bearing programs to the medical treatment of elderly patients with osteoporosis". Journal of Family & Community Medicine. 21 (3): 176–181. doi:10.4103/2230-8229.142972. PMC 4214007. PMID 25374469.

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