OVERVIEW
Hypophosphatemia is defined as a serum inorganic phosphorus concentration below 0.8 mmol/L (2.5 mg/dl). Hypophosphatemia is not uncommon and occurs in people of all ages and genders. In mild cases, it is asymptomatic, but in severe cases, it can lead to serious clinical consequences.
Causes
The causes of hypophosphatemia are as follows.
1. Decreased phosphorus intake or malabsorption
It can be seen in fasting or starvation (which can lead to phosphorus depletion in the body and secondary hypophosphatemia after refeeding, especially during intravenous glucose infusion), vomiting and diarrhea, 1,25-dihydroxyvitamin D3 deficiency, malabsorption syndrome, and the use of phosphate-binding acidulators (aluminum hydroxide gel, aluminum carbonate, magnesium hydroxide), and so on.
2. Excessive renal phosphorus excretion
See acute alcoholism, primary or secondary hyperparathyroidism, renal tubular acidosis, vitamin D resistance rickets, metabolic acidosis, diabetes mellitus, and the use of glucocorticoids and diuretics.
3. Phosphorus to the intracellular transfer
See respiratory or metabolic alkalosis, and the application of anabolic insulin, androgens and so on.
Symptoms
Hypophosphatemia mainly causes adenosine triphosphate synthesis insufficiency and the decrease of 2,3-diphosphoglycerate in erythrocytes.
1. Mild hypophosphatemia has no obvious symptoms.
2. Severe hypophosphatemia can lead to serious clinical consequences, but the symptoms are usually nonspecific.
(1) Neuropsychiatric symptoms manifested as agitation, abnormal perilabial sensation, and in severe cases, confusion, rigidity, convulsions, coma, and even death.
(2) Skeletal and muscular symptoms include muscle weakness, muscle paralysis, and sensory abnormalities, weakness, staggering gait, bone pain, rickets, and pathologic fractures. Severe hypophosphatemia can occur due to hypoxia and acute respiratory failure caused by reduced contractility of the heart muscle and diaphragm.
(3) Cardiovascular system symptoms: severe hypophosphatemia, due to energy metabolism disorders, can lead to severe cardiomyopathy, decreased cardiac output, hypotension, and even congestive heart failure.
(4) Digestive system symptoms: chronic hypophosphatemia patients often have loss of appetite, anorexia, nausea, vomiting, and in severe cases, gastric hypotonia, intestinal paralysis and dysphagia.
Examination
1. Laboratory examination
Check electrolytes, osmolality, blood glucose, blood ketone body, 1,25-dihydroxyvitamin D3, parathyroid hormone, renal function, creatine kinase, blood gas analysis, urinary protein, urinary ketone body, 24-hour urinary phosphorus/calcium and so on.
2. Imaging examination
Including bone X-ray, parathyroid B ultrasound, etc.
Diagnosis
Check the serum inorganic phosphorus level, if the blood phosphorus <0.8 mmol/L, the diagnosis of hypophosphatemia can be confirmed.
Treatment
1. Remove the cause and treat the original disease
Mild or moderate hypophosphatemia is often asymptomatic or has mild symptoms, and the intake of phosphorus can be increased by increasing the amount of phosphorus-rich foods, such as milk, fish, meat, etc. In addition, the focus should be on finding and treating the cause of hypophosphatemia. In addition, we should focus on finding and treating the primary cause of hypophosphatemia.
2. Intravenous phosphorus supplementation
When the blood phosphorus level decreases to 0.32 mmol/L (1mg/dL), phosphorus should be supplemented. Because a large number of oral phosphorus-containing compounds are easy to cause diarrhea, therefore, most of the phosphorus supplementation using intravenous route, intravenous phosphorus supplementation preparation commonly used potassium phosphate.
During phosphorus supplementation, attention should be paid to calcium supplementation to prevent the occurrence of severe hypocalcemia.
Questions you may be concerned about
How to test for hypophosphatemia
Hypophosphatemia can be detected by blood phosphorus measurement, urine phosphorus measurement, blood calcium test, parathyroid hormone measurement, and other tests such as X-ray.
1. Blood phosphorus measurement: normal adult serum phosphorus is less than 0.83mmol/L, children’s serum phosphorus is less than 1.45mmol/L, mostly considered to be caused by hypophosphatemia. General serum phosphorus in 0.3 ~ 0.8mmol / L, mostly considered to be mild or moderate hypophosphatemia. If the serum phosphorus is lower than 0.3mmol/L, it is severe hypophosphatemia.
2. Urine phosphorus measurement: Hypophosphatemia patients urine phosphorus test is found to be less than 1.25mmol / L, can be excluded is the renal loss of hypophosphatemia. If the patient has increased urinary phosphorus excretion, it is considered to be caused by rickets, primary renal tubular abnormalities.
3. Blood calcium examination: hypophosphatemia with decreased blood calcium is considered to be caused by vitamin D deficiency, alkalosis, long-term malnutrition and other factors. If hypophosphatemia patients with elevated blood calcium, it is considered to be caused by hyperparathyroidism.
4. Determination of parathyroid hormone: patients with hypophosphatemia will have elevated parathyroid hormone, which is mostly considered to be caused by oncological osteochondrosis, renal tubular lesions.
5. Other: patients with hypophosphatemia also need to do X-ray, nuclear magnetic resonance, urine excretion component test.
It is recommended that patients with hypophosphatemia need to consult a doctor in a timely manner, and the doctor will take the appropriate test according to the patient’s condition.