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Osteoporosis - Coggle Diagram
Osteoporosis
Pathogenesis
Osteoporosis occurs when the bones become so porous and brittle that they can fracture very easily under mild stress.
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This can occur when there is a calcium deficiency in the body and the parathyroid hormone becomes overactive (hyperparathyroidism) and degrades the calcium from the bones, making them weak and porous.
This can also occur from aging, as the bone mass naturally decreases with age (especially with women after menopause since they lose the protective effects of estrogen). After menopause when estrogen levels decrease, the RANKL cytokine is produced which activates more osteoclasts that degrade the bone. This causes the bones to weaken to the point where pathological fractures are likely to happen.
A bone tumor can also cause osteoporosis due to the tumor degrading the calcium from the bone, leaving them weak and porous.
The number of osteoblasts also decrease with aging, which limits the ability for those cells to build up the bone and prevent osteoporosis.
Incidence/Prevalence
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1 in 5 men worldwide over the age of 50 will experience a pathological fracture related to osteoporosis.
Osteoporosis is very rare in pediatric patients but does occur in children most commonly due to secondary disease processes.
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Risk Factors
Women are at a higher risk after menopause since they lose the protective effects of estrogen and they have a lower bone density than men.
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Men and women who have a genetically smaller frame are more likely to develop osteoporosis since there is less bone mass to begin with.
People who have hyperthyroidism/hyperparathyroidism are at risk for osteoporosis since it can cause bone loss.
People who have a low calcium intake (especially when they're young) will be at an increased risk for osteoporosis since they have less calcium in the bones that can be degraded into the blood when serum calcium levels get low.
Patients who are taking certain drugs, such as steroids, may be at an increased risk for osteoporosis.
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References
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Quiros Roldan, E., Brianese, N., Raffetti, E., Focà, E., Pezzoli, M. C., Bonito, A., Ferraresi, A., Lanza, P., Porcelli, T., & Castelli, F. (2017). Comparison between the gold standard DXA with calcaneal quantitative ultrasound based-strategy (QUS) to detect osteoporosis in an HIV infected cohort. The Brazilian Journal of Infectious Diseases, 21(6), 581-586. https://doi.org/10.1016/j.bjid.2017.08.003
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Diagnostics
Osteoporosis can be diagnosed with a DXA scan (dual-energy x-ray absorptiometry) which can be used to analyze one's bone density to calculate the risk for osteoporosis. A Z-score of -2.5 or below on these scans will indicate osteoporosis.
Central DXA scans are recommended in the hips and spine since those are common places for pathological fractures in osteoporosis and can detect early risk for those fractures.
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Quantitative ultrasounds can also be used to visualize the bone density and diagnose osteoporosis, but a DXA scan is still the most accurate method of diagnosis.
Quantitative Computed Tomography scans are also used to analyze bone density and are used as a tool for diagnosing osteoporosis.
Calcium and Vitamin D levels in bloodwork are analyzed, since hypocalcemia and low vitamin D can add to osteoporosis.
Parathyroid hormone levels are also checked because hyperparathyroidism can degrade the calcium from the bone and contribute to osteoporosis.
Osteoporosis in children is very rare, but diagnosed with the same labs and scans that are used for diagnosis in adults. A child will be diagnosed with osteoporosis if the bone mineral content has a percentile of at least 2.0 less than the mean for their age.
Clinical Manifestations
The patient might experience vertebral fractures due to the weight of the body fracturing the porous vertebrae.
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Patients might also lose their lumbar curvature (lumbar lordosis) due to the compression fractures of the vertebral column.
Patients might have issues with balancing, since they can get kyphosis in the spine which results in an unsteady gait.
The patient may experience pain in the wrists and hips from pathological fractures resulting from the brittle and porous bones.
Height may decrease in some patients due to the compression and loss of bone density in the vertebral column.
Patients might get decreased range of motion in the extremities due to the weakening of the bones and subsequent pathological fractures.
Children with osteoporosis will often have pain in the hips, issues with ambulation, kyphosis, and an abnormal chest shape. They might also experience fractures in the long bones of the lower extremities and compression fractures in the vertebrae.
Treatments
Biphosphonates such as Alendronate, Risedronate, and Ibandronate are first-line medications used to treat osteoporosis. These medications work by limiting the activity of osteoclasts to keep the calcium in the bones to increase bone density. A patient who takes this class of medications must be able to sit upright for 30 minutes after administration and must take it with one glass of water.
SERMS (selective estrogen receptor modifiers) such as Tamoxifen is another class of medication that is used to treat osteoporosis and works by mimicking the effects of estrogen in the body to reduce the calcium loss in the bone in the case of osteoporosis.
Patients should increase their dietary intake of calcium or take calcium and vitamin D supplements to increase the amount of calcium in their bones to make them less porous.
For children with osteoporosis, increasing calcium and vitamin D intake as well as using biphosphonates can help reduce the signs and symptoms of osteoporosis.
Increasing weight-bearing exercises can strengthen the bones to decrease the risk of pathological fractures with osteoporosis.
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Teriparatide is a hormonal drug that can help decrease the effects of osteoporosis by stimulating osteoblasts to make more bone. This drug can have serious side effects for patients who are at risk for cardiovascular or cerebrovascular diseases. This drug is contraindicated in pregnant/breast-feeding mothers and patients with severe renal diseases.
Denosumab is a monoclonal antibody that decreases the activity of osteoclasts to slow the progression of osteoporosis. This drug is safe to use in renal failure patients and is used as a first-line therapy for patients with inflammatory and autoimmune diseases.
Calcitonin is a hormonal medication that reduces the activity of osteoclasts and preserves the calcium in the bone to lessen the effects of osteoporosis. It is no longer widely used because it was causing epistaxis and flushing.