Osteoporosis
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Alcoholism p. 595
osteoporosis and p. 472
Anticoagulant drugs p. 420
osteoporosis and p. 472
Anticonvulsant drugs
osteoporosis and p. 472
Bisphosphonates p. 499
for osteoporosis p. 472
Calcitonin p. 343
osteoporosis p. 472
Corticosteroids
osteoporosis with p. 251
Denosumab p. 120
for osteoporosis p. 472
Estrogen p. 654, 680
osteoporosis p. 472
Geriatric patients
osteoporosis p. 472
Heparin p. 443
osteoporosis p. 251
Hyperparathyroidism p. 344
osteoporosis p. 472
Hyperthyroidism p. 346, 348, 671
osteoporosis p. 472
Malabsorption syndromes p. 390, 390
osteoporosis p. 472
Multiple myeloma p. 438
osteoporosis p. 472
Osteoporosis p. 472
bisphosphonates p. 499
corticosteroids p. 118
Cushing syndrome p. 354
denosumab p. 120
as drug reaction p. 251
estrogen p. 472
Gaucher disease p. 86
heparin p. 443
homocystinuria p. 83
hormone replacement therapy p. 680
lab values in p. 472
menopause p. 652
pituitary prolactinomas p. 335
raloxifene for p. 451, 680
teriparatide for p. 500
thiazides for p. 633
vertebral compression fractures p. 730
Steroids
osteoporosis and p. 472
Vitamin D
osteoporosis prophylaxis p. 472
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Osteo- refers to bones and -porosis means pores.
So, osteoporosis is when there’s a higher breakdown of bone in comparison to the formation of new bone which results in porous bones, meaning a decrease in bone density to the point of potential fracture.
Looking at a cross-section of a bone, there’s a hard-external layer known as the cortical bone and a softer internal layer of spongy bone or trabecular bone that is composed of trabeculae.
The trabeculae are like a framework of beams that give structural support to the spongy bone.
The cortical bone, in turn, is made up of many functional, pipe-like units called osteons, which run through the length of the bone.
In the center of these osteons, there are hollow spaces called Haversian canals, which contain the blood supply and innervation for the bone cells.
Around the Haversian canals, there are concentric lamellae, which look a bit like tree rings.
The lamellae have an organic part, which is mostly collagen, and an inorganic part called hydroxyapatite, which is mostly calcium phosphate.
In between neighboring lamellae, there are spaces called lacunae, which contain bone cells called osteocytes.
At first glance, bone may appear inert and unchanging, but it’s actually a very dynamic tissue.
In fact, spongy bone is replaced every 3 to 4 years and compact bone is replaced every 10 years, in a process called bone remodeling, which has two steps: bone resorption, when specialized cells called osteoclasts break down bone, and bone formation, which is when another type of cells called osteoblasts form new bone.
Bone remodelling as a whole is highly dependent on serum calcium levels, which, in turn, are kept in the normal range by a balance between parathyroid hormone, or PTH, calcitonin and vitamin D.
Parathyroid hormone is produced by the parathyroid glands in response to low serum calcium, and it increases bone resorption to release calcium into the bloodstream.
On the other hand, calcitonin is produced by the thyroid gland in response to high serum calcium, so it opposes the action of PTH - therefore promoting bone formation and decreasing bone resorption.
Summary
Osteoporosis refers to decreased bone density due to increased bone resorption compared to bone formation. Commonly affected bones include vertebrae, forearm, and hip. Osteoporosis is typically asymptomatic until a broken bone occurs; such breaks may occur spontaneously or with minor stress because of the disease's unremarkable progression. The treatment involves bisphosphonate drugs like alendronate and risedronate.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Bone Resorption by Osteoclasts" Science (2000)
- "Normal Bone Anatomy and Physiology" Clinical Journal of the American Society of Nephrology (2008)
- "Osteoporotic compression fractures of the spine; current options and considerations for treatment" The Spine Journal (2006)
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