What Is Calcium Toxicity?

Vitamin D poisoning is one of the iatrogenic diseases. It is mainly caused by misdiagnosis and excessive use of vitamin D preparations in the prevention and treatment of rickets, such as cod liver oil, vitamin D ₂ (calciferol), vitamin D ₂ (cholcalciferol or bilirubin), and vitamin g colloidal calcium.

Basic Information

English name

vitamin D toxication

Visiting department

Emergency Department

Common causes

Vitamin D intake by the body

Common symptoms

Loss of appetite, even anorexia, irritability, crying, loss of energy, and more low fever

Causes of vitamin D poisoning

When the body ingests a large amount of vitamin D, the feedback function of vitamin D in the body is dysfunctional, the intestinal absorption of calcium and phosphorus increases, the blood calcium concentration is too high, and the regulation of calcitonin causes blood calcium to deposit in bone and other organs and tissues, affecting its function. For example, calcium salts deposited in the kidney can cause renal tubular necrosis and renal calcification. In severe cases, renal atrophy and chronic renal damage can occur. Calcium salts deposited in the small bronchus and alveoli, damage the respiratory epithelial cells and cause ulcers, or calcifications. System, cardiovascular and other important organs and tissues have more calcifications, which can cause irreversible serious damage.

Clinical manifestations of vitamin D poisoning

The earliest symptoms are loss of appetite, and even anorexia, irritability, crying, depression, and low fever. May also have sweating, nausea, vomiting, diarrhea or constipation, gradually appearing thirst, frequent urination, nocturia, and occasionally dehydration and acidosis. Older children can have headaches, blood pressure can rise or fall, the heart can smell and systolic murmurs, the ST segment of the ECG can rise, and sometimes mild anemia. In severe cases, depression, hypotonia, dyskinesia, coma and convulsions, and renal failure may occur. Urine specific gravity is low and fixed, urine protein is positive, cells are increased, and casts are also possible. Long-term chronic poisoning can cause corresponding calcification of bones, kidneys, blood vessels and skin, affecting physical and intellectual development, and severe cases can cause death due to renal failure. Vitamin D poisoning in early pregnancy can cause fetal malformations.

Vitamin D poisoning test

Laboratory inspection

Serum 25 hydroxy D increased, serum calcium increased (> 3.0mmol / L (12mg / dl)), blood phosphorus and alkaline phosphatase were normal or slightly lower. Normal or elevated plasma cholesterol. In a few cases, urea nitrogen is elevated, and renal function is abnormal, such as low and fixed urine specificity, positive urine protein, and casts with increased cells.

2.X-ray inspection

Metaphyseal sclerosis is one of the common X-ray signs of vitamin D poisoning, but it is not characteristic. The reliable X-ray signs of vitamin D poisoning are: the southern bone of the ulna and radial shaft is blurry and has a periosteal reaction; cortical osteoporosis or osteoporosis; the infarcted zone of the metaphyseal end of the ulna and radial bone or "poor" The diaphyseal cortex is thickened and dense; cartilage bone nucleus calcification ring thickened and hardened.

Vitamin D poisoning can be diagnosed if three of the above five types of X-ray signs appear at the same time. Of course, it must be combined with clinical history and VitD overdose to confirm the diagnosis. Severe poisoning can still show metastatic calcification of the kidney, blood vessels, heart and soft tissues of the extremities.

Diagnosis of vitamin D poisoning

Vitamin D poisoning is more common with general symptoms and lacks special manifestations. Therefore, mild symptoms are often not easy to notice, and even VitD is considered to be early symptoms of rickets. When the symptoms are obvious, they are easily misdiagnosed as other diseases. The main basis is:

1. A history of excessive VitD application, such as a daily dose of more than 4000U, a history of consecutive months or repeated high-dose intramuscular injections.

2. Increased blood calcium and positive urine calcium.

3. X-ray photo is abnormal. However, it should be noted that the X-ray changes during early poisoning are not obvious, the serum calcium is not high during the period of recovery and sequelae of poisoning, and the symptoms of poisoning and the dose of VitD do not work. In medical practice, large doses are not too rare, but poisoning is not too common, which is likely related to the metabolic characteristics of VitD. X-ray abnormalities are common in long-term chronic poisoning cases. Serum 25-OHD and serum calcium are elevated in the early stages of acute poisoning, followed by changes in the epiphysis. During the course of treatment, blood calcium recovers first, and epiphyseal X-ray examinations gradually recover later. A positive X-ray can help diagnose, while a negative X-ray does not deny vitamin D poisoning.

Differential diagnosis of vitamin D poisoning

Infection must be excluded with low fever. Polyuria is easily misdiagnosed as a urinary tract infection, but treatment with antibiotics is not satisfactory. The occurrence of hypercalcemia should be distinguished from infant idiopathic hypercalcemia, hyperparathyroidism, malignant tumor bone metastases, and hypoalkaline phosphatase. Idiopathic hypercalcemia is similar to vitamin D poisoning, but there is no history of overactive VitD. The symptoms of hyperparathyroidism are the same as those of vitamin D poisoning, and blood calcium is also elevated, but the X-ray shows general osteoporosis, and treatment with adrenal corticosteroids is ineffective. In addition, the X-ray bones alone need to be distinguished from rickets recovery period, lead, and fluorosis, and must be considered in combination with medical history, signs, bismuth, and blood calcium.

Vitamin D poisoning treatment

1. VitD preparations and calcium should be stopped immediately after diagnosis of vitamin D poisoning, avoid sunlight, and give a low calcium diet.

2. Control infection and correct dehydration acidosis. Generally, the patients should recover gradually after the above treatment for a long time, the blood calcium will return to normal after about 2 to 3 months, and the renal function can be delayed after 18 months to recover.

3. Special therapy: Adrenocortical hormone can inhibit the absorption of calcium in the intestine, and has an antagonistic effect on VitD. Prednisone is orally administered at 1 to 2 mg / kg / d. After 1 to 2 weeks, the blood calcium level drops to normal. Generally, it is discontinued for 2 to 3 weeks, and the blood calcium level no longer rises. In severe cases, the medication time can be appropriately extended according to blood calcium and X-ray pictures. Oral sulfuric acid can reduce the absorption of calcium, and 1 to 2 g can be used for older children.

Vitamin D poisoning prevention

1. Master the dosage of VitD for prevention or treatment. The preventive dose should not exceed 400U orally per day. Parents should be educated about the dangers of excessive VitD overdose.

2. The patient should be asked in detail the dose of VitD used in the past before the surprise treatment. Most of the poisoning cases are based on long-term oral cod liver oil, and the symptoms of poisoning are more likely to occur after D2 or D3 injection. Therefore, the indications must be grasped before using large doses.

3. When the general VitD dose is not satisfactory, the blood calcium, phosphorus and alkaline phosphatase should be checked before deciding whether to use assault therapy.

4. The prevention and treatment of general nutritional rickets should avoid large-dose VD assaults as much as possible. When high-dose VitD treatment must be applied, closely observe clinical symptoms, and determine whether there is any sign of poisoning in blood calcium every month, and check every half month if necessary.

5. Practice has proved that VD20U has the same effect as 400,000 U. When a large dose of VitD is required for assault treatment, it is best not to exceed 20U, and generally no second injection is required. Oral VitD in children with normal liver, kidney, and gastrointestinal functions has the same effect as intramuscular injection. It is safe to take orally, and intramuscular injection is not necessary when not necessary.