Osteoporosis

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Osteoporosis

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USMLE® Step 1 style questions USMLE

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A 62-year-old woman comes to her outpatient provider for a routine visit. The patient has no acute complaints. Past medical history is notable for hypertension, for which she is currently taking propranolol. She consumes 3-4 glasses of wine per week and smokes half-a-pack of cigarettes per day. The patient’s brother passed away from multiple myeloma 4 years ago. Temperature is 37.1°C (98.8°F), blood pressure is 138/75 mmHg, and BMI is 19 kg/m2. The physician is concerned that the patient may have osteoporosis. Which of the following laboratory findings will most likely confirm this diagnosis?  

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Alcoholism p. 589

osteoporosis and p. 467

Anticoagulant drugs p. 418

osteoporosis and p. 467

Anticonvulsant drugs

osteoporosis and p. 467

Bisphosphonates p. 495

for osteoporosis p. 467

Calcitonin p. 341

osteoporosis p. 467

Corticosteroids

osteoporosis with p. 249

Denosumab p. 120

for osteoporosis p. 467

Estrogen p. 648, 674

osteoporosis p. 467

Geriatric patients

osteoporosis p. 467

Heparin p. 440

osteoporosis p. 249

Hyperparathyroidism p. 342

osteoporosis p. 467

Hyperthyroidism p. 344, 346, 665

osteoporosis p. 467

Malabsorption syndromes p. 388, 388

osteoporosis p. 467

Multiple myeloma p. 436

osteoporosis p. 467

Osteoporosis p. 467

bisphosphonates p. 495

corticosteroids p. 118

Cushing syndrome p. 352

denosumab p. 120

as drug reaction p. 249

estrogen p. 467

Gaucher disease p. 86

heparin p. 440

homocystinuria p. 83

hormone replacement therapy p. 674

lab values in p. 467

menopause p. 646

pituitary prolactinomas p. 333

raloxifene for p. 447, 674

teriparatide for p. 496

thiazides for p. 627

vertebral compression fractures p. 733

Steroids

osteoporosis and p. 467

Vitamin D

osteoporosis prophylaxis p. 467

Transcript

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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 remodeling 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. Finally, vitamin D promotes calcium absorption in the gut, so it increases serum calcium, 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

  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Bone Resorption by Osteoclasts" Science (2000)
  6. "Normal Bone Anatomy and Physiology" Clinical Journal of the American Society of Nephrology (2008)
  7. "Osteoporotic compression fractures of the spine; current options and considerations for treatment" The Spine Journal (2006)
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