Definition
- Deficient PTH secretion causing hypocalcaemia and hyperphosphataemia
Aetiology
- Surgical removal or injury of parathyroids, most often after thyroidectomy
- Autoimmune, isolated or within autoimmune polyendocrine syndrome type 1
- DiGeorge syndrome (22q11.2 deletion)
- Hypomagnesaemia impairs PTH secretion and is reversible
Clinical Features
- Perioral and digital paraesthesia, muscle cramps and tetany
- Chvostek sign, facial twitch on tapping the facial nerve anterior to the ear
- Trousseau sign, carpal spasm with a BP cuff above systolic pressure for three minutes
- Seizures, laryngospasm and prolonged QT
- Cataracts and basal ganglia calcification with long standing disease
Investigations
- Low calcium, high phosphate and low or inappropriately normal PTH
- Check magnesium and vitamin D
- X-ray shows increased bone density and soft tissue calcification
- Paraspinal ligament calcification and enthesopathy can mimic DISH
Differential Diagnosis
- Pseudohypoparathyroidism, with raised PTH
- Vitamin D deficiency, with raised PTH and low phosphate
Management
- Acute tetany treated with IV calcium gluconate under cardiac monitoring
- Long term oral calcium with active vitamin D such as calcitriol
- High dose ergocalciferol is an older alternative with greater toxicity risk
- Recombinant PTH for patients poorly controlled on conventional therapy
- Aim for low normal calcium to limit hypercalciuria
Complications
- Nephrocalcinosis, renal stones and renal impairment from treatment
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.