Etiology and mechanisms of development
The main trigger of the disease is a massive intake of cholecalciferol into the body, which exceeds permissible norms by tens of times. The key risk group consists of premature newborns and infants in the first year of life. This is due to the immaturity of their detoxification enzyme systems. As the child grows older, tolerance to the drug increases significantly as the enzyme systems of the liver and kidneys reach functional maturity.
The pathogenetic basis of hypervitaminosis is hypercalcemia. Excess calcium circulates in the bloodstream and exerts a direct toxic effect. This leads to the following disorders:
- Profound damage to the structure of cell membranes.
- Pronounced shifts in acid-base balance (ABB).
- A sharp suppression of the excretory and metabolic functions of the liver, as well as the kidneys.
Clinical picture depending on age
The symptom complex of vitamin D intoxication varies greatly depending on the patient's age.
In infants of the first year of life, signs of general intoxication and gross disorders of water balance dominate. Due to excess calcium, polyuria occurs (increased urine output), which compensatorily causes polydipsia (severe thirst). Infants refuse to eat, vomit frequently and profusely, and rapidly lose body weight. Ultimately, these processes lead to severe dehydration of the body.
In older children, vascular and neurological pathologies come to the fore in the clinical picture. Patients complain of intense headaches and pronounced general weakness. Objective examination reveals arterial hypertension. In severe cases, the toxic effect on the central nervous system provokes the development of seizure syndrome.
Complications and laboratory diagnostics
The main danger of the disease lies in the development of ectopic calcification — the deposition of calcium salts in soft tissues where they should not be. This leads to formidable complications: angiocalcinosis (vascular damage), nephrocalcinosis, and the formation of secondary dysmetabolic pyelonephritis.
To confirm the diagnosis, a comprehensive laboratory evaluation is required:
- Blood test: hypercalcemia and hyperphosphatemia are detected against the background of a paradoxical decrease in parathyroid hormone (PTH) levels. A specific and most accurate marker of overdose is an increase in the concentration of the 25(OH)D metabolite above 100 ng/mL.
- Urine test: hypercalciuria is noted. At the same time, calcium excretion of more than 2 mg/kg of body weight is recognized as the most accessible, rapid, and reliable diagnostic criterion.
Principles of treatment and prevention
Therapy for patients with hypervitaminosis D is carried out exclusively in a hospital setting, specifically in the nephrology department.
The treatment regimen includes:
- Elimination of the cause: immediate and complete discontinuation of any vitamin D preparations, as well as strict exclusion of ultraviolet irradiation (insolation).
- Antidote therapy: administration of direct antagonists — vitamin A (retinol) and the hormone calcitonin.
- Forced diuresis: active infusion therapy in combination with diuretics for the accelerated flushing out of excess calcium. This stage requires the strictest monitoring of calcium and phosphorus levels in blood and urine.
Prevention is divided into non-specific (breastfeeding, adequate daily routine, sufficient sun exposure, obtaining calcium only from food without dietary supplements) and specific. Specific prevention is carried out with cholecalciferol at a universal dose of 400–600 IU/day, which is prescribed to all children without exception, regardless of the season and type of feeding.
Vitamin D antagonists are easy to remember by the acronym "ARC" — Antagonists: Retinol, Calcitonin.
Class and exam questions
In which hospital department is treatment carried out?
Therapy is carried out strictly in a hospital setting; the nephrological department is the appropriate profile, as the urinary system takes the primary hit.
Is it necessary to cancel the prophylactic dose of vitamin D in summer?
No, you don't need to. The prophylactic dosage of 400–600 IU/day is universal and is prescribed regardless of the season and the nature of the child's feeding.
Which urine indicator is key in diagnosis?
The most accessible and reliable criterion is hypercalciuria — urinary calcium excretion exceeding 2 mg/kg of body weight.
What else to study on this topic
- Mechanisms of development of ectopic tissue calcification
- Pathogenesis of dysmetabolic pyelonephritis in hypercalciuria
- Features of water-electrolyte disorders in infants (polyuria and polydipsia)
- Interaction of vitamin D with parathyroid hormone (PTH) and phosphorus
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