AKT · Endocrine/Calcium, bone & parathyroidlow yield

Hypoparathyroidism

PTH deficiency (post-surgical, autoimmune) or PTH resistance (pseudohypoparathyroidism)

Overview

Deficiency of PTH — most commonly after thyroid/parathyroid surgery, or autoimmune (± polyglandular syndrome), causing HYPOcalcaemia with HIGH phosphate and low/inappropriate PTH. Pseudohypoparathyroidism is end-organ PTH resistance (high PTH, with skeletal features). Treated with calcium and active vitamin D.

Recognise

Hypocalcaemia symptoms: perioral/peripheral paraesthesiae, muscle cramps, carpopedal spasm, TETANY; Chvostek and Trousseau signs
Severe: laryngospasm, seizures, prolonged QT (arrhythmia)
Biochemistry: low calcium, HIGH phosphate, low/inappropriately-low PTH (post-surgical/autoimmune)

Red flags

Acute symptomatic hypocalcaemia (tetany, seizures, laryngospasm, long QT) → IV calcium gluconate
Post-thyroidectomy hypocalcaemia → monitor calcium

Differentials & how to tell them apart

Vitamin D deficiency / CKDhypocalcaemia with HIGH PTH (secondary hyperparathyroidism) — opposite PTH

Pseudohypoparathyroidismhypocalcaemia with HIGH PTH (resistance), short stature/short 4th metacarpals (Albright)

Hypomagnesaemialow magnesium impairs PTH — correct magnesium first

Investigations

Calcium (low), phosphate (high), PTH (low/inappropriate), magnesium, vitamin D; ECG (long QT). Pseudohypoparathyroidism: high PTH with resistance (± Albright features).

Management

Calcium + active vitamin D (IV calcium gluconate if severe/symptomatic)

1Acute symptomatic hypocalcaemia → IV calcium gluconate with cardiac monitoring. Maintenance: oral calcium + active vitamin D (alfacalcidol/calcitriol). Correct magnesium.Gate: Check and correct MAGNESIUM — hypomagnesaemia causes refractory hypocalcaemia that won't respond to calcium until magnesium is replaced; the high phosphate + low PTH distinguishes true hypoparathyroidism from vitamin D deficiency (high PTH)
2Long-term monitoring of calcium/phosphate/renal function; recombinant PTH in selected refractory cases.

Calcium + active vitamin D (alfacalcidol/calcitriol) — maintenance replacement

IV calcium gluconate (acute/severe) — for tetany/seizures/long QT — with cardiac monitoring

Correct magnesium — hypomagnesaemia must be corrected for PTH/calcium to respond

Key points

Low calcium + HIGH phosphate + low PTH = hypoparathyroidism (often post-surgical). Tetany, Chvostek/Trousseau, long QT. Always correct magnesium. High PTH instead = vitamin D deficiency or pseudohypoparathyroidism.

Monitor & prognosis

Calcium, phosphate, renal function; ECG if severe.

Manageable with replacement.

Source: Society for Endocrinology