Assessment of hypocalcaemia

Hypocalcaemia is a state of electrolyte imbalance in which the circulating serum calcium level is low. During hypocalcaemia, the total calcium level and the ionised calcium level fall below the laboratory reference range.

Hypocalcaemia 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 hypocalcaemia largely manifest through neuromuscular excitability. Hypocalcaemia can present acutely and be life threatening; early recognition and correction is critical. Quantitatively severe hypocalcaemia can sometimes present with few symptoms, if onset has been protracted and chronic.

Pathophysiology

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 signalling.

Circulating calcium levels are impaired by several factors, but hypocalcaemia 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 ionised 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 ionised form.[1]Cooper MS, Gittoes NJ. Diagnosis and management of hypocalcaemia. BMJ. 2008 Jun 7;336(7656):1298-302. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2413335 http://www.ncbi.nlm.nih.gov/pubmed/18535072?tool=bestpractice.com

Signs and symptoms

Hypocalcaemia varies from a mild asymptomatic biochemical abnormality to a life-threatening disorder. Acute hypocalcaemia can lead to paraesthesia, tetany, and seizures (characteristic physical signs may be observed, including Chvostek's sign, which is neither sensitive nor specific for hypocalcaemia, and Trousseau's sign).[2]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. https://ec.bioscientifica.com/view/journals/ec/5/5/G7.xml http://www.ncbi.nlm.nih.gov/pubmed/27935815?tool=bestpractice.com [3]Jesus JE, Landry A. Images in clinical medicine. Chvostek's and Trousseau's signs. N Engl J Med. 2012 Sep 13;367(11):e15. https://www.doi.org/10.1056/NEJMicm1110569 http://www.ncbi.nlm.nih.gov/pubmed/22970971?tool=bestpractice.com [Figure caption and citation for the preceding image starts]: Carpopedal spasm (Trousseau's sign) occurred a few minutes after inflation of a sphygmomanometer cuff above systolic blood pressurePedrazzini B et al. BMJ Case Reports 2010;2010:bcr.08.2009.2188 [Citation ends].

Papilloedema, cataracts, basal ganglia calcifications, and skin, hair, and dental changes may occur with chronic hypocalcaemia.[4]Pepe J, Colangelo L, Biamonte F, et al. Diagnosis and management of hypocalcemia. Endocrine. 2020 Sep;69(3):485-95. http://www.ncbi.nlm.nih.gov/pubmed/32367335?tool=bestpractice.com ​ Neuropsychiatric manifestations include dementia in adults, anxiety, depression, lethargy, and extrapyramidal symptoms (parkinsonism).[4]Pepe J, Colangelo L, Biamonte F, et al. Diagnosis and management of hypocalcemia. Endocrine. 2020 Sep;69(3):485-95. http://www.ncbi.nlm.nih.gov/pubmed/32367335?tool=bestpractice.com [5]Maiti A, Chatterjee S. Neuropsychiatric manifestations and their outcomes in chronic hypocalcaemia. J Indian Med Assoc. 2013 Mar;111(3):174-7. http://www.ncbi.nlm.nih.gov/pubmed/24592758?tool=bestpractice.com [6]Hall A, Bin Farooq T, Alcaraz R Jr. Hypocalcemia-induced reversible psychosis. Cureus. 2022 Jan 2;14(1):e20874. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8805771 http://www.ncbi.nlm.nih.gov/pubmed/35145781?tool=bestpractice.com ​​ Skin examination may show dermatitis, eczema, hyperpigmentation, psoriasis, brittle hair with patchy alopecia, and brittle nails with characteristic transverse grooves.[Figure caption and citation for the preceding image starts]: Nail dystrophy due to hypocalcaemiaNijjer S et al. BMJ Case Reports 2010;2010:bcr.08.2009.2216 [Citation ends]. Patients rarely may have congestive heart failure, angina, and hypotension.