Hypophosphatemia
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: Hypophosphataemia; phosphate levels low (plasma or serum).
Overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Hypophosphatemia is an electrolyte disturbance in which there is an abnormally low level of phosphate in the blood. The condition has many causes, but is most commonly seen when malnourished patients (especially chronic alcoholics) are given large amounts of carbohydrates, which create a high phosphorus demand by cells, removing phosphate from the blood (refeeding syndrome).
Because a decrease in phosphate in the blood is sometimes associated with an increase in phosphate in the urine, the terms hypophosphatemia and “phosphaturia” are occasionally used interchangeably; however, this is improper since there exist many causes of hypophosphatemia besides overexcretion and phosphaturia, and in fact the most common causes of hypophosphatemia are not associated with phosphaturia.
Treatment
Medical Therapy
Standard intravenous preparations of potassium phosphate are available and are routinely used in malnurished patients and alcoholics. Oral supplementation also is useful where no intravenous treatment is available. Historically one of the first demonstrations of this was in concentration camp victims who died soon after being re-fed: it was observed that those given milk (high in phosphate) had a higher survival rate than those who did not get milk.
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Historical Perspective
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Classification
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Pathophysiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Pathophysiology
Hypophosphatemia is caused by the following three mechanisms:
- Inadequate intake (often unmasked in refeeding after long-term low phosphate intake)
- Increased excretion (e.g. in hyperparathyroidism)
- Shift from extracellular to intracellular space (seen in treatment of diabetic ketoacidosis, refeeding, short-term increases in cellular demand (e.g., hungry bones syndrome) and acute respiratory alkalosis)
References
Causes
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Causes
- Refeeding syndrome This causes a demand for phosphate in cells due to the action of phosphofructokinase, an enzyme which attaches phosphate to glucose to begin metabolism of this. Also, production of ATP when cells are fed and recharge their energy supplies, requires phosphate.
- Respiratory alkalosis Any alkalemic condition moves phosphate out of the blood into cells. This includes most common respiratory alkalemia (a higher than normal blood pH from low carbon dioxide levels in the blood), which in turn is caused by any hyperventilation (such as sepsis, fever, pain, anxiety, drug withdrawal).
- Alcohol abuse Alcohol impairs phosphate absorption, and alcoholics are also after malnurished with regard to minerals. In addition, alcohol treatment is associated with refeeding, and the stress of alcohol withdrawal may create respiratory alkalosis, which exacerbates hypophosphatemia (see above).
- Malabsorption This includes GI damage, and also failure to absorb phosphate due to lack of vitamin D, or chronic use of phosphate binders such as sucralfate, aluminum-containing antacids, and (more rarely) calcium-containing antacids.
- Hyperexcretion of phosphate in the urine (phosphaturia). This includes excess excretion from renal dysfunction, and also the action of many classes of diuretics. Additionally, both primary and secondary hyperparathyroidism causes hyperexcretion of phosphate in the urine.
Causes by Organ System
| Cardiovascular | No underlying causes |
| Chemical/Poisoning | No underlying causes |
| Dental | No underlying causes |
| Dermatologic | No underlying causes |
| Drug Side Effect | Cabozantinib, Cefepime, Felbamate, Gallium nitrate , Lanthanum carbonate, Niacin, Nilotinib, Pamidronic acid, Sorafenib, Streptozocin |
| Ear Nose Throat | No underlying causes |
| Endocrine | No underlying causes |
| Environmental | No underlying causes |
| Gastroenterologic | No underlying causes |
| Genetic | No underlying causes |
| Hematologic | No underlying causes |
| Iatrogenic | No underlying causes |
| Infectious Disease | No underlying causes |
| Musculoskeletal/Orthopedic | No underlying causes |
| Neurologic | No underlying causes |
| Nutritional/Metabolic | No underlying causes |
| Obstetric/Gynecologic | No underlying causes |
| Oncologic | No underlying causes |
| Ophthalmologic | No underlying causes |
| Overdose/Toxicity | No underlying causes |
| Psychiatric | No underlying causes |
| Pulmonary | No underlying causes |
| Renal/Electrolyte | No underlying causes |
| Rheumatology/Immunology/Allergy | No underlying causes |
| Sexual | No underlying causes |
| Trauma | No underlying causes |
| Urologic | No underlying causes |
| Miscellaneous | No underlying causes |
Causes in Alphabetical Order
Other rarer causes include
- Certain blood cancers such as lymphoma or leukemia
- Hereditary causes
- Hepatic failure
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Differentiating Hypophosphatemia from other Diseases
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Epidemiology and Demographics
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Risk Factors
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Natural History, Complications and Prognosis
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Diagnosis
Diagnosis
History and Symptoms | Physical Examination | Laboratory Findings | Electrocardiogram | X Ray | Arterial Blood Gas | Bone Densitometry | Ultrasound | Other Imaging Findings | Other Diagnostic Studies
Treatment
Treatment
Medical Therapy | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies
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