Hypocalcaemia

Disease class: Calcium metabolism disorders 
Disease class: Water-electrolyte imbalance

This refers to calcium levels in the blood below the reference range.

 

Aetiology / Causes

Low PTH (hypoparathyroidism)

• Genetic disorders
• Abnormal parathyroid gland development
• Abnormal PTH synthesis
• Activating mutations of calcium-sensing receptor (autosomal dominant hypocalcaemia or sporadic isolated hypoparathyroidism)
• Postsurgical
• Thyroidectomy
• Parathyroidectomy
• Radical neck dissection
• Autoimmune
• Autoimmune polyglandular syndrome (associated with chronic mucocutaneous candidiasis and primary adrenal insufficiency)
• Isolated hypoparathyroidism due to activating antibodies to calcium-sensing receptor
• Infiltration of the parathyroid gland (granulomatous, iron overload, metastases)
• Radiation-induced destruction parathyroid glands
• Hungry bone syndrome (post-parathyroidectomy)
• HIV infection

High PTH (secondary hyperparathyroidism in response to hypocalcaemia)

• Vitamin D deficiency or resistance
• Multiple causes
• PTH resistance
• Missense mutation in PTH
• Pseudohypoparathyroidism
• Hypomagnesaemia
• Kidney diseases
• Loss of calcium from the circulation
• Hyperphosphataemia
• Tumor lysis
• Acute pancreatitis
• Osteoblastic metastases
• Acute respiratory alkalosis
• Sepsis or acute severe illness

Drugs

• Inhibitors of bone resorption (bisphosphonates, calcitonin, denosumab), especially in vitamin D deficiency
• Cinacalcet
• Calcium chelators (EDTA, citrate, phosphate)
• Foscarnet (due to intravascular complexing with calcium)
• Phenytoin (due to conversion of vitamin D to inactive metabolites)
• Fluoride poisoning

Disorders of magnesium metabolism

• Hypomagnesaemia can reduce PTH secretion or cause PTH resistance and is therefore associated with normal, low, or high PTH levels.

 

Management

• Calcium and vitamin D

 

 See also

• Hypercalcaemia