Hypocalcemia is a state of electrolyte imbalance in which the circulating serum calcium level is low. During hypocalcemia, the total calcium level and the ionized calcium level fall below the laboratory reference range.
Hypocalcemia may occur subsequent to failure of any of the mechanisms by which serum calcium concentration is maintained. But it is usually the result of failure of parathyroid hormone secretion or an inability to release calcium from bone.
The clinical features of hypocalcemia largely manifest through neuromuscular excitability. Hypocalaemia can present acutely and be life threatening; early recognition and correction is critical. Quantitatively severe hypocalcemia can sometimes present with few symptoms, if onset has been protracted and chronic.
Calcium is one of the most abundant electrolytes in the body, and levels are tightly controlled by parathyroid hormone and vitamin D. Calcium is essential for cell function, cell membrane stability, neuronal transmission, bone physiology, blood homeostasis, and cell signaling.
Circulating calcium levels are impaired by several factors, but hypocalcemia is mainly secondary to the imbalance of calcium absorption, excretion, and distribution.
As 40% of circulating calcium is bound to albumin, in a ratio of 1 mg albumin to 0.8 mg calcium, measuring albumin is essential in interpreting total serum calcium levels. However, if ionized calcium is determined, there is no need to measure albumin or adjust the value of calcium concentration. Approximately 15% of circulating calcium is bound to sulfates, phosphates, lactate, and citrate, and the remaining 45% circulates as biologically active calcium in an ionized form.
Signs and symptoms
Hypocalcemia varies from a mild asymptomatic biochemical abnormality to a life-threatening disorder. Acute hypocalcemia can lead to paresthesia, tetany, and seizures (characteristic physical signs may be observed, including Chvostek sign, which is poorly sensitive and specific of hypocalcemia, and Trousseau sign).
Papilledema, cataracts, basal ganglia calcifications, and skin, hair, and dental changes may occur with chronic hypocalcemia. Neuropsychiatric manifestations include dementia in adults, anxiety, depression, lethargy, and extrapyramidal symptoms (parkinsonism). Skin exam may show dermatitis, eczema, hyperpigmentation, psoriasis, brittle hair with patchy alopecia, and brittle nails with characteristic transverse grooves. Patients rarely may have congestive heart failure, angina, and hypotension.
- Iatrogenic postsurgical hypoparathyroidism
- Vitamin D deficiency
- Isolated hypoparathyroidism
- Autoimmune hypoparathyroidism
- HIV-related hypoparathyroidism
- Renal failure
- Acute pancreatitis
- Extensive osteoblastic skeletal metastasis
- Hungry bone syndrome
- Drug-induced hypocalcemia
- Multiple transfusions
- Drug interference with assay
- Infiltrative hypoparathyroidism
- DiGeorge syndrome and other developmental complexes
- Tumor lysis syndrome
- Constitutively activating calcium sensing receptor (CaSR) abnormalities (mutations or autoimmune activation)
- Vitamin D resistance or receptor mutations
Use of this content is subject to our disclaimer