Introduction to hypocalcaemia
Hypocalcaemia is often asymptomatic, but patients may present with generalised signs of neuromuscular irritability such as tetany (often including positive Chvostek and Trousseau signs).
Hypocalcaemia is diagnosed on the basis of a low serum total calcium concentration corrected for albumin (normal range 2.10 to 2.60 mmol/L). If the albumin concentration is significantly abnormal, serum ionised calcium should be measured directly.
Common causes of hypocalcaemia are listed in Common causes of hypocalcaemia.
Severe vitamin D deficiency [NB1]
Autoimmune hypoparathyroidism
Parathyroid injury following thyroidectomy or parathyroidectomy
Hypoparathyroidism related to congenital disorders (eg DiGeorge syndrome)
Hypomagnesaemia (including in association with malabsorption, alcohol abuse and proton pump inhibitors)
Antiresorptive drugs (bisphosphonates and denosumab)
Autosomal dominant hypocalcaemia
Neonate of a mother with hypercalcaemia
Vitamin D–dependent rickets type 1 or 2 [NB2]
NB1: Severe vitamin D deficiency in children with nutritional deficiency is the most common cause of hypocalcaemia in children.
NB2: Vitamin D–dependent rickets type 1 is a deficiency of the enzyme that catalyses the conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D. Vitamin D–dependent rickets type 2 is a mutation of the vitamin D receptor gene, leading to resistance to 1,25-dihydroxyvitamin D.