AKT · Endocrine/Calcium, bone & parathyroid

Hypercalcaemia

Raised calcium (90% primary hyperparathyroidism or malignancy)

Overview

Raised serum (corrected) calcium. ~90% is either primary hyperparathyroidism (commonest in the well outpatient) or malignancy (commonest in the unwell inpatient — PTHrP, bony metastases, myeloma). PTH is the pivotal test: raised/normal = parathyroid; suppressed = malignancy/other. Severe hypercalcaemia is treated with IV fluids then a bisphosphonate.

Recognise

'Stones, bones, abdominal groans, psychic moans, thrones (polyuria)' — renal stones, bone pain, constipation/nausea, confusion/depression, polyuria/polydipsia
Short QT on ECG; dehydration; in malignancy often rapid and symptomatic
Mild and chronic (hyperparathyroidism) vs acute and unwell (malignancy)

Red flags

Severe (>3.5 mmol/L) or symptomatic (confusion, dehydration, arrhythmia) → emergency IV fluids + bisphosphonate
New hypercalcaemia in a smoker/weight loss → investigate for malignancy

Differentials & how to tell them apart

Primary hyperparathyroidismPTH raised/inappropriately normal, low phosphate, well outpatient

Malignancy (PTHrP / bony mets / myeloma)PTH SUPPRESSED, unwell, rapid; known/occult cancer

FHHmild, LOW urine calcium, benign family history — do not treat as hyperparathyroidism

Vitamin D toxicity / sarcoidosis / thiazides / immobility / milk-alkaliPTH suppressed; specific contexts

Investigations

Corrected calcium + PTH (the key discriminator) + phosphate; renal function; if PTH suppressed → investigate malignancy (myeloma screen, imaging, PTHrP), vitamin D, sarcoid (ACE), TSH. Urine calcium (exclude FHH).

Management

IV fluids first, then IV bisphosphonate; treat the cause

1Check PTH to split parathyroid (raised/normal PTH) from non-parathyroid (suppressed PTH) causes. Severe/symptomatic → IV 0.9% saline rehydration, then IV bisphosphonate; stop contributing drugs (thiazides, calcium/vitamin D).Gate: Rehydrate with saline FIRST — bisphosphonates take a few days and the immediate problem is volume depletion; PTH level directs the work-up (parathyroidectomy vs cancer hunt)
2Treat the cause: parathyroidectomy (hyperparathyroidism); oncological treatment ± denosumab (malignancy); steroids (sarcoid/vitamin D/myeloma).

IV 0.9% saline (rehydration) — first-line for severe/symptomatic — restores volume and promotes calcium excretion

IV bisphosphonate (zoledronate) — after rehydration — reduces osteoclastic resorption (works over days)

Calcitonin / denosumab / steroids (specific causes) — calcitonin faster but transient; steroids for sarcoid/vitamin D/myeloma

Key points

PTH is the fork: raised/normal = hyperparathyroidism, suppressed = malignancy (or other). Fluids before the bisphosphonate. FHH (low urine calcium) is the benign trap not to operate on.

Monitor & prognosis

Calcium, renal function, ECG.

Depends on cause.

Source: Society for Endocrinology; CKS Hypercalcaemia