Hypervitaminosis D

The toxic effect of high doses of vitamin D has been known since 1929. Hypervitaminosis D can occur with unreasonable prescription of the drug without taking into account individual sensitivity to "shock" doses. Individual reactions to the introduction of vitamin D can be caused by both genetic factors and changes that have occurred in the child's body under the influence of environmental factors.

An overdose of vitamin D has both a direct and indirect toxic effect on the child's body - through disruption of phosphorus-calcium homeostasis and the development of hypercalcemia. Excessive intake of vitamin D into the blood leads to a sharp increase in calcium absorption in the intestine and causes bone resorption.

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Symptoms of hypervitaminosis D

Symptoms of hypervitaminosis D are well studied and look like acute toxicosis or chronic intoxication (the differences depend on the child's age, duration of vitamin D administration). Acute toxicosis most often occurs in children in the first half of life, when large doses of vitamin D are prescribed in a short period of time. In the second half of the year, chronic intoxication may develop (with prolonged use of small doses of vitamin D). The main symptoms are: anorexia, hypotrophy, asthenia, nausea, vomiting, developmental delay, constipation, polyuria, polydipsia, dehydration and convulsions. The degree of damage to the nervous system varies from mild inhibition to severe comatose states.

• There are three degrees of hypercalcemia:
• first degree - the calcium content in the blood is stable at the upper limit of the norm, it is intensively excreted in the urine (Sulkovich reaction +++), the clinical picture is moderate toxicosis, polyuria, polydipsia, weight loss;
• the second degree - the calcium content in the blood is higher than normal, but does not exceed 12 mg%, the Sulkovich reaction is +++ or ++++, in the clinical picture - severe toxicosis, polyuria, dystrophy;
• third degree - calcium content in the blood is more than 12 mg%, severe toxicosis and mandatory kidney damage.

The intensity of cardiovascular damage varies from minor functional disorders to severe myocarditis with circulatory failure. In case of liver damage, the activity of serum transaminases may be increased, dysproteinemia is possible, the blood cholesterol level may be increased, the ratio of α- and β-lipoproteins may be disturbed; pathological types of glycemic curves have been described. Kidney damage varies from minor dysuric phenomena to acute renal failure; leukocyturia, minor hematuria and proteinuria are characteristic; secondary infection and development of pyelonephritis often occur; nephrocalcinosis: oxalate-calcific urolithiasis. With the progression of these diseases, chronic renal failure develops.

Damage to the respiratory system and gastrointestinal tract is rare.

Diagnosis of hypervitaminosis D

The diagnosis of hypervitaminosis D is made when a complex of biochemical changes is detected (hypercalciuria, hypercalcemia, hypophosphatemia and hyperphosphaturia, acidosis are possible). Radiologically, intensive deposition of lime in the epiphyseal zones of tubular bones and increased porosity of the diaphyses can be established. The bones of the skull are compacted. The large fontanelle closes early. Anamnesis data on the intake of vitamin D, especially in high doses, are important.

The Sulkovich test is widely used in diagnosis. In hypercalciuria, a mixture of Sulkovich reagent with double the amount of urine immediately produces a gross turbidity, whereas in healthy children a slight milky turbidity occurs immediately or after a few seconds.

However, the test is not reliable enough, so in doubtful cases it is necessary to simultaneously check the calcium and phosphorus levels in the blood.

After hypervitaminosis D, nephropathy often develops: chronic pyelonephritis, interstitial nephritis, tubulopagia. 

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Tactics of managing children with hypervitaminosis D

Hypervitaminosis D may take an atypical course. If intoxication caused by vitamin D preparations is suspected, it is necessary to immediately stop taking the preparation and discontinue administration of calcium salts. Products rich in calcium are excluded from the child's diet: whole cow's milk, kefir, cottage cheese, if possible replacing them with expressed breast milk (fractional feeding). Prescribe plenty of tea, 5% glucose solution and prescribe vitamin A at 5000-10,000 IU (2 drops 2-3 times a day, vitamins B, E. At the same time, it is necessary to do the Sulkovich test, examine the calcium content in the patient's blood serum. Acute toxicosis with vitamin D is treated in a hospital setting; in addition to the above measures, drip administration of fluids is prescribed (5% glucose solution, 0.9% sodium chloride solution) based on the daily requirement.

In cases of severe intoxication, glucocorticoids are indicated to promote the excretion of calcium in the urine. Prednisolone is prescribed at 1.0-1.5 mg per 1 kg of body weight per day for 8-12 days.

Properly organized general hygiene regimen, aerotherapy, massage, therapeutic gymnastics, individual care are important. As the signs of intoxication disappear, the patient's diet can be expanded.

Children who have suffered from vitamin D intoxication should be observed in a polyclinic for 2-3 years. Periodically, it is necessary to examine urine analysis and kidney function tests, pay attention to the state of the cardiovascular system, and monitor electrocardiographic indicators.

How to prevent hypervitaminosis D?

Prevention of hypervitaminosis D is closely related to rational prevention of rickets. When prescribing any vitamin D preparations, it is important to remember about its possible toxic effect, so the dose should be determined as accurately as possible, summing up all sources of vitamin D intake. The development of hypervitaminosis is inhibited by the simultaneous administration of vitamins A and B.

When carrying out prevention, it is important to take into account the individual sensitivity of the child to vitamin D; to clarify this, it is necessary to carefully collect anamnesis and systematically monitor the child's condition. Premature and artificially and mixed-fed children are regularly (once a week) given the Sulkovich test during the period of vitamin D use to detect the first signs of intoxication.