Evaluation of hypocalcemia

Summary

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.[1]

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, vitamin D deficiency, or an inability to release calcium from bone.

The clinical features of hypocalcemia largely manifest through neuromuscular excitability.[2] Hypocalaemia can present acutely and be life threatening; early recognition and correction is critical.[3] Quantitatively severe hypocalcemia can sometimes present with few symptoms, if onset has been protracted and chronic.[2] [4]

Pathophysiology

Calcium is one of the most abundant electrolytes in the body, and is essential for cell function, cell membrane stability, neuronal transmission, bone physiology, blood homeostasis, and cell signaling.[5] [6]

Approximately 40% of circulating calcium is bound to proteins (mostly albumin), 13% is bound to anions (such as sulfates, phosphates, lactate, citrate, and bicarbonate), and the remaining 47% circulates as biologically active calcium in an ionized form.[7]

Calcium levels are tightly controlled by parathyroid hormone and vitamin D. When serum calcium levels decrease, secretion of parathyroid hormone increases. As a result, there is increased reabsorption of calcium in the kidneys, bone resorption, and vitamin D secretion. Vitamin D causes increased calcium absorption in the gastrointestinal tract.[2] [6]

Circulating calcium levels are impaired by several factors, but hypocalcemia is mainly secondary to the imbalance of calcium absorption, excretion, and distribution.[6]

Library

Carpopedal spasm (Trousseau sign) occurred a few minutes after inflation of a sphygmomanometer cuff above systolic blood pressure
Nail dystrophy due to hypocalcemia
Electrocardiogram (ECG) showing an adjusted QT interval (QTc) of 503 ms while in sinus rhythm

Citations

Key Articles

Hannan FM, Thakker RV. Investigating hypocalcaemia. BMJ. 2013 May 9;346:f2213.
Cooper MS, Gittoes NJ. Diagnosis and management of hypocalcaemia. BMJ. 2008 Jun 7;336(7656):1298-302.[Abstract][Full Text]
Turner J, Gittoes N, Selby P, et al. Society for endocrinology endocrine emergency guidance: emergency management of acute hypocalcaemia in adult patients. Endocr Connect. 2016 Sep;5(5):G7-8.[Abstract][Full Text]

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