Causes of Decreased Calcium Levels
Blood calcium concentration is tightly regulated, and its drop always indicates a serious underlying disorder. Key factors contributing to hypocalcemia include:
- Endocrine disorders: The most common cause is the surgical removal or immune-mediated damage of the parathyroid glands, leading to hypoparathyroidism. This inhibits calcium release from bones and stimulates its renal excretion. Hypersecretion of calcitonin (a direct antagonist of parathyroid hormone) also leads to deficiency.
- Gastrointestinal and absorption issues: Vitamin D deficiency, chronic enteritis, malabsorption syndromes, or small bowel resection critically impair ion absorption. Acholia (the absence of bile in the intestine) plays a major role. Without bile, luminal and membrane digestion as well as fat-soluble vitamin D metabolism are disrupted.
- Metabolic shifts: Chronic uncompensated alkalosis (respiratory or metabolic, with respiratory being more common in children) actively binds ionized calcium. Hypomagnesemia suppresses parathyroid hormone secretion and blocks its effects in bone tissue. Hypoalbuminemia decreases total calcium due to a reduction in the protein-bound fraction.
- Associated conditions: Calcium deficiency often accompanies cerebral palsy, autism, anorexia, and kidney disease. It can develop against the background of severe stress, infections, dysbiosis, candidiasis, and heavy metal poisoning.
Pathogenesis: How Seizures Occur
The primary danger of hypocalcemia is a pronounced bathmotropic effect, which is the pathological increase in neuromuscular excitability.
Under normal physiological conditions, calcium ions block sodium channels on cell membranes. When calcium concentration in the interstitial space drops, this protective block is removed. As a result, the depolarization threshold is significantly lowered, and the excitation of nerve and muscle cells is greatly facilitated. Cells begin to respond to the slightest stimulus. The clinical outcome of this cascade includes muscle spasms, tetany attacks, and severe cardiac arrhythmias.
Clinical Presentation and Complications
If calcium levels drop slowly and mildly, symptoms may remain absent for a long time. However, significant hypocalcemia manifests brightly and affects multiple systems:
- Neuromuscular system and CNS: Patients complain of numbness in the extremities and paresthesias (tingling sensations) in the hands, feet, and around the mouth. Muscle spasms and cramps occur. Impaired consciousness is possible.
- Cardiovascular system: Myocardial contractility drops, and arrhythmias develop. In severe cases, cardiac arrest may occur.
- Hemostasis: Contrary to common misconceptions, blood clotting does not increase; it decreases. Blood rheology is impaired, leading to increased fragility and bleeding of vascular walls.
- Tissue changes: Ectodermal derivatives are affected. Dystrophy of teeth, hair, nails, and the eye lens develops. Connective tissue dysplasia (up to generalized forms) is also observed.
- Chronic manifestations: Prolonged deficiency leads to rickets, abnormal dental development, and frequent bone fractures secondary to osteoporosis.
Treatment Approaches
The most effective approaches to treating hypocalcemia include several strategies:
- Elimination of the cause (etiotropic therapy): Since hypoparathyroidism is the most frequent cause, parathyroid hormone replacement therapy forms the basis of treatment.
- Management of acute hypocalcemia: Tetany attacks and acute seizure states require immediate intravenous calcium administration (calcium gluconate is most commonly used).
- Treatment of chronic forms: Oral preparations (calcium carbonate or calcium gluconate) are prescribed in strict combination with vitamin D (ergocalciferol, calcitriol).
- Correction of acid-base balance: Performed in the presence of alkalosis, as alkalosis shifts calcium into a bound form and reduces its active ionized fraction.