Bone
Non-neoplastic or metabolic disease
Osteoporosis

Author: Nat Pernick, M.D. (see Authors page)

Revised: 4 October 2016, last major update August 2013

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Osteoporosis[title]
Cite this page: Osteoporosis. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/boneosteoporosis.html. Accessed December 5th, 2016.
Definition / General
  • Reduction in bone mass due to increased bone porosity, which predisposes bones to fracture
  • Usually refers to postmenopausal or senile loss of bone severe enough to cause fractures
  • Affects entire skeleton due to metabolic bone disease, but may be localized due to limb disuse
  • Usually due to increased bone resorption, with normal levels of bone formation
  • Osteopenia: defined as radiologic decrease in density of skeleton
  • Primary causes: due to postmenopausal condition, older age (15 million cases in US) or idiopathic
  • Secondary causes (due to identifiable conditions): endocrine (hyperparathyroidism, thyroid disorders, hypogonadism, pituitary tumors, type I diabetes, Addison’s disease), neoplasms (myeloma, carcinomatosis), gastrointestinal disturbances (malnutrition, deficiency of vitamins C or D), drugs (corticosteroids, chemotherapy), osteogenesis imperfecta, immobilization, homocystinuria, anemia
  • Menopause: postmenopausal women may lose 2% of cortical bone and 9% of cancellous bone / year; osteoporosis affects women more than men because estrogen deficiency leads to increased osteoclast activity, and osteoblasts cannot keep pace
  • Age related changes: osteoblasts have reduced reproductive and biosynthetic potential in elderly
  • Immobilization: important cause because mechanical forces stimulate bone remodeling; zero gravity (astronauts), immobilization cause reduced skeletal mass; athletes have higher bone density; weight training is more effective than jogging in increasing skeletal mass
  • Genetics: variation in Vitamin D receptor type accounts for 75% of maximal peak bone mass achieved; Vitamin D intake and parathyroid hormone levels are not significant causes, although low calcium intake in women is an important cause
  • Other risk factors: Whites / Asians, smoking, alcohol abuse
  • Bone mass: peak bone mass occurs in young adults, based on physical activity, muscle strength, diet, hormones; subsequent remodeling causes small deficit in bone formation with each resorption / ormation cycle, which causes bone loss of 0.7% per year
  • Sites: cancellous compartment of vertebral bone (with high surface area) affected first, causing loss of vertebral height in elderly, leading to dowager’s hump; also thinning of cortex; hip and wrist also affected
Radiology Description
  • Flattening of vertebral bodies, widening and swelling of intervertebral discs, fish - mouth appearance
  • Usually thoracic and upper lumbar spine
Diagnosis
  • Radiographic measurement of bone density, iliac crest biopsy
Treatment
  • Calcium, Vitamin D and exercise to build up / maintain bone mass
  • Biphosphonates (inhibit post-menopausal bone loss)
Gross Description
  • Loss of cancellous bone, accentuation of vertical trabeculae in spine
Micro Description
  • Thin trabeculae disconnected from each other
  • Increase in osteoclastic activity (may be uneven) or increased percentage of surface with resorptive pitting
Micro Images

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Osteoporosis