Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Both disorders can present with acute symptomatic hypocalcaemia
Tetany, seizure, laryngospasm, prolonged QT or arrhythmia demands the adult acute hypocalcaemia pathway before genetic or mechanistic refinement. Vomiting or missed activated vitamin D can destabilise established hypoparathyroidism, while severe magnesium deficiency may mimic low PTH.
Action: Use ABCDE and ECG monitoring, measure ionised or adjusted calcium, phosphate, magnesium, renal function and PTH, and give intravenous calcium gluconate when symptomatic or severely low. Correct magnesium and involve endocrinology for transition to oral calcium and activated vitamin D.
Synopsis
Separate absent PTH from end-organ PTH resistance, manage chronic calcium safely, and recognise genetic and multi-hormone implications requiring specialist care.
Hypoparathyroidism produces low calcium and high phosphate with PTH that is low or inappropriately normal, most often after anterior neck surgery.
Pseudohypoparathyroidism produces a similar calcium-phosphate pattern but PTH is raised because target tissues resist its signal.
Severe magnesium depletion can suppress PTH secretion and action, so it must be corrected before declaring permanent gland failure.
Investigation priorities
01
Concurrent calcium, phosphate and PTHFirst step
Distinguish inadequate PTH secretion from an appropriately raised but ineffective PTH response.
Management branches
ClassifyRead PTH in context
Persistent hypocalcaemia and hyperphosphataemia suggest parathyroid-axis disease.
Confirm true low calcium and measure PTH, phosphate, magnesium, kidney function and vitamin D from the same physiological period.
Correct significant magnesium deficiency and review surgery, autoimmune history, CKD and medicines before concluding gland loss or resistance.
Key medicines
Calcitriol or alfacalcidolBegin and adjust the activated vitamin D preparation in small specialist-guided increments according to symptoms, calcium, phosphate, kidney function and urine calcium, following the local product-specific regimen.
Oral calciumUse a divided elemental-calcium regimen selected for dietary intake, symptoms and activated vitamin D dose, with product and timing documented because different salts contain different elemental amounts.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.