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Musculoskeletal system




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USMLE® Step 1 questions

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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. 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


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


osteoporosis and p. 472

Vitamin D

osteoporosis prophylaxis p. 472


Content Reviewers

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.


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.


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