Hypercalcaemia and primary hyperparathyroidism: the GP approach

What hypercalcaemia means in general practice

Hypercalcaemia is a corrected serum calcium above 2.55 mmol/L (laboratory reference ranges vary slightly). It is one of the most common unexpected abnormalities found on routine blood tests in general practice — and in most ambulatory patients, the cause is primary hyperparathyroidism (PHPT) or, less commonly, malignancy. Together these two diagnoses account for over 90% of hypercalcaemia seen in general practice.

eTG complete and RACGP resources note that PHPT has become predominantly an asymptomatic disease discovered on routine pathology, rather than one presenting with the classical “stones, bones, abdominal groans, and psychic moans” picture. The shift reflects widespread routine biochemistry testing, catching disease while the calcium elevation is still mild.

Efficient workup rests on one central distinction: is the parathyroid hormone (PTH) driving the hypercalcaemia, or is PTH appropriately suppressed? This single biochemical question restructures the differential and avoids unnecessary investigation.

A. Core clinical — the AU general practice framework

Confirming the calcium elevation

A single high calcium reading is frequently spurious — haemoconcentration, lab variation, or prolonged tourniquet time can artefactually raise the result. Always:

• Corrected calcium for albumin: corrected Ca = total Ca + 0.02 × (40 − albumin g/L). Most Australian laboratories report this automatically.
• Ionised calcium when albumin is abnormal, in acid-base disorders, or where corrected and total values diverge.
• Repeat on a second fasting morning sample — per eTG complete, one confirmation before proceeding to extensive investigation avoids unnecessary workup from transient artefacts.

The PTH-based diagnostic framework

Measuring intact PTH alongside the repeat calcium is the single most informative step:

PTH-dependent hypercalcaemia (PTH inappropriately normal or elevated with high calcium):

• Primary hyperparathyroidism — the most common cause of ambulatory hypercalcaemia; autonomous PTH oversecretion from a parathyroid adenoma (80–85%), four-gland hyperplasia (10–15%), or rarely multiple adenomas or carcinoma.
• Familial hypocalciuric hypercalcaemia (FHH) — autosomal dominant calcium-sensing receptor (CaSR) mutation; biochemically resembles PHPT but is clinically benign. Distinguished by a urinary calcium-to-creatinine ratio below 0.01. Parathyroidectomy is not indicated for FHH.
• Lithium therapy — elevates the CaSR set-point.
• Tertiary hyperparathyroidism — autonomous PTH secretion after prolonged secondary hyperparathyroidism in chronic kidney disease.

PTH-independent hypercalcaemia (PTH appropriately suppressed):

• Malignancy — PTHrP secretion from squamous lung, breast, or renal cell carcinoma; lytic bone metastases (breast cancer, multiple myeloma); calcitriol production in lymphoma, sarcoidosis, or tuberculosis.
• Vitamin D toxicity — from supplementation or granulomatous disease converting 25-OH vitamin D to active 1,25-(OH)₂ vitamin D.
• Hyperthyroidism (thyrotoxicosis).
• Adrenal insufficiency (Addison’s disease).
• Milk-alkali syndrome (high calcium carbonate ingestion).
• Thiazide diuretics — raise tubular calcium reabsorption; may unmask mild PHPT.
• Immobilisation, particularly with underlying Paget’s disease.

The mnemonic CHIMPANZEES (Calcium ingestion, Hyperparathyroidism, Immobilisation/Iatrogenic, Milk-alkali, Paget’s, Addison’s, Neoplasm, Zollinger-Ellison/MEN, Excess vitamin D/A, Endocrine — thyrotoxicosis, Sarcoidosis/granulomatous) covers the full differential for reference.

Primary hyperparathyroidism: who it affects

Per the Fourth International Workshop guidelines (Bilezikian et al. JCEM 2014; updated 2022):

• Incidence approximately 25 per 100,000 per year; prevalence around 1% in women over 65.
• Female-to-male ratio approximately 3:1; peak in the postmenopausal decade.
• Most patients are asymptomatic at diagnosis.

Clinical features, when present:

• Renal — nephrolithiasis (calcium oxalate or phosphate), nephrocalcinosis, polyuria and polydipsia from nephrogenic diabetes insipidus.
• Skeletal — osteoporosis preferentially affecting cortical bone (distal radius, hip), bone pain, fragility fractures.
• Gastrointestinal — anorexia, nausea, constipation; pancreatitis is rare.
• Neurocognitive — fatigue, low mood, cognitive slowing.
• Cardiovascular — hypertension; whether PHPT increases cardiovascular risk independently is debated in the literature.

Genetic syndromes warrant consideration in patients under 40, those with a family history, or multi-gland disease: MEN-1 (PHPT with pancreatic islet tumours and pituitary adenoma), MEN-2A (PHPT with medullary thyroid carcinoma and phaeochromocytoma), hyperparathyroidism-jaw tumour syndrome (HPT-JT; elevated parathyroid carcinoma risk), and familial isolated hyperparathyroidism (FIHP).

Diagnostic workup in general practice

Step 1 — Confirm hypercalcaemia and measure PTH simultaneously. Order: corrected calcium (or ionised calcium), intact PTH, phosphate, alkaline phosphatase (ALP), 25-OH vitamin D, and kidney function (U&E/eGFR/creatinine). A suppressed PTH redirects workup toward malignancy (myeloma screen: SPEP, free light chains, urine BJP; CXR and CT chest; thyroid function; oncological workup as indicated by clinical context).

Step 2 — Urine calcium-to-creatinine ratio. A spot or 24-hour urine ratio distinguishes PHPT from FHH: PHPT typically ≥0.02; FHH typically below 0.01. RACGP guidance recommends this before any surgical referral — failing to identify FHH leads to parathyroidectomy in a condition that does not benefit from it.

Step 3 — Vitamin D repletion. Vitamin D deficiency masks and worsens PHPT by lowering the calcium reading. NHMRC reference values support a target 25-OH vitamin D of at least 50 nmol/L (many endocrinologists aim for ≥75 nmol/L in PHPT). Replete and recheck before finalising the biochemical picture.

Surgical criteria for PHPT

The Fourth International Workshop (updated 2022) recommends parathyroidectomy for PHPT if any one of the following applies:

• Age under 50.
• Corrected serum calcium more than 0.25 mmol/L above the laboratory upper limit of normal.
• eGFR below 60 mL/min/1.73 m².
• 24-hour urine calcium above 10 mmol per day with nephrolithiasis risk, or documented kidney stones or nephrocalcinosis on imaging.
• DEXA T-score ≤−2.5 at any site, or vertebral fracture.
• Symptomatic hypercalcaemia or PHPT-related complications.

If no criteria are met, conservative monitoring is the recommended approach. Discuss with an endocrinologist before concluding no criteria are present — normocalcaemic hyperparathyroidism (elevated PTH with consistently normal calcium after vitamin D repletion) is a separate diagnostic category with its own monitoring needs.

Conservative monitoring plan

Per the ESA/ANZBMS position statement:

• Annual corrected calcium and eGFR.
• DEXA bone density every one to two years, including distal radius for cortical bone.
• 24-hour urine calcium every one to two years if initial values were borderline.
• Annual symptom review: renal colic, low mood, cognitive change, gastrointestinal symptoms.
• Ensure adequate vitamin D status.
• Adequate calcium intake (1000–1200 mg per day) — dietary calcium restriction is counterproductive in PHPT, worsening secondary hyperparathyroidism and accelerating bone loss. This is counterintuitive and frequently misapplied; confirm the advice with the treating endocrinologist.

B. Evidence appraisal — what the data show

Parathyroidectomy

For PHPT meeting at least one surgical criterion, parathyroidectomy is the most effective treatment. The 2022 updated Fourth International Workshop guidelines and Walker and Silverberg’s 2018 review in Nature Reviews Endocrinology confirm:

• Resolution of hypercalcaemia in the large majority of patients treated at high-volume endocrine surgery centres.
• Improvement in bone mineral density, particularly at the lumbar spine and hip.
• Reduction in nephrolithiasis recurrence.
• Minimally invasive parathyroidectomy (MIP) is standard for localised single adenoma confirmed on pre-operative imaging; bilateral neck exploration for multi-gland disease.
• Complications: recurrent laryngeal nerve injury (~1%), transient hypoparathyroidism (~10%), permanent hypoparathyroidism (under 2%).

Pre-operative localisation: sestamibi parathyroid scan combined with neck ultrasound is standard. Where results are discordant or negative, 4D CT parathyroid or SPECT-CT is used. Imaging is for localisation only — it does not confirm or exclude the diagnosis of PHPT, which is biochemical.

Medical management

Cinacalcet — a calcimimetic that sensitises the calcium-sensing receptor to calcium — reduces PTH and corrected calcium in PHPT. Per the PBS, cinacalcet carries an Authority Required indication for inoperable PHPT meeting specific clinical criteria, parathyroid carcinoma, and severe secondary hyperparathyroidism in dialysis patients. Dose 30–90 mg twice daily; nausea and hypocalcaemia are common adverse effects. Cinacalcet reduces serum calcium but does not substantially improve bone density, unlike surgery.

Per AMH, bisphosphonates (alendronate, zoledronic acid) and denosumab offer bone protection in PHPT patients who are not surgical candidates. These agents produce modest secondary calcium lowering but are not primary calcium-lowering treatments.

NICE NG132 aligns with the Fourth International Workshop criteria for conservative monitoring intervals and surgical thresholds; Australian practice refers primarily to the international workshop guidelines.

C. Acute severe hypercalcaemia — emergency management

Acute severe hypercalcaemia — corrected calcium above approximately 3.0–3.5 mmol/L with symptoms — is a medical emergency requiring hospital admission. Symptoms include confusion, drowsiness, profound dehydration, severe vomiting, muscle weakness, polyuria, shortened QT interval on ECG, and arrhythmia.

The eTG acute care approach follows a stepwise inpatient protocol:

1. IV isotonic saline 200–500 mL/hour to restore circulating volume and promote renal calcium excretion. Four to six litres over the first 24 hours is typical. Exercise caution in older patients and those with cardiac or renal impairment to avoid fluid overload.

2. Calcitonin 4 IU/kg subcutaneous or intramuscular every 12 hours for the first 24–48 hours. Onset within 4–6 hours; tachyphylaxis limits it to short-term bridge use while bisphosphonate takes effect.

3. IV bisphosphonate — zoledronic acid 4 mg IV over 15 minutes is preferred (faster onset and longer duration than pamidronate). Pamidronate 60–90 mg IV over 2–4 hours is an alternative. Onset 24–72 hours; effect lasts weeks. Dose-reduce for eGFR below 30 mL/min or consider alternative agents.

4. Denosumab 120 mg subcutaneously — alternative when eGFR is below 30 mL/min or bisphosphonate is contraindicated. Effective in malignancy-related hypercalcaemia; watch for profound hypocalcaemia after the calcium falls.

5. Glucocorticoids (prednisolone 20–40 mg/day) — for vitamin D-mediated and granulomatous hypercalcaemia (sarcoidosis, lymphoma, tuberculosis). Not appropriate for PHPT.

6. Haemodialysis — reserved for refractory hypercalcaemia with severe renal failure or cardiac failure where IV fluids cannot be safely administered.

7. Treat the underlying cause — surgery for PHPT, chemotherapy for haematological malignancy, corticosteroids for granulomatous disease, discontinue thiazide or lithium if implicated.

D. Australian operations

MBS items in hypercalcaemia management

Per MBS Online, relevant items in general practice:

• Items 23/36/44 — Level B/C/D GP attendances.
• Items 715/707 — ATSI Health Assessment and 75+ Health Assessment (metabolic conditions included).
• Pathology items for calcium, PTH, phosphate, ALP, 25-OH vitamin D, U&E, and urine collections.
• Items 12306/12320 — DEXA bone densitometry.
• Item 55700 — neck ultrasound (pre-operative localisation, specialist-ordered).
• Item 61425 — sestamibi parathyroid nuclear scan (specialist-ordered).
• Items 30533/30536 — parathyroidectomy (endocrine surgical items).
• Items 132/133 — specialist physician (endocrinology) initial and subsequent consultations.

PBS prescribing

From the PBS schedule:

• Cinacalcet (Sensipar) — Authority Required (Telephone) for inoperable PHPT meeting defined criteria, parathyroid carcinoma, and secondary hyperparathyroidism in dialysis; not available for operable PHPT.
• Zoledronic acid (Aclasta/Zometa) — Authority Required for osteoporosis, Paget’s disease, and hypercalcaemia of malignancy under specified criteria.
• Pamidronate — General Schedule for hypercalcaemia and Paget’s disease.
• Denosumab (Xgeva 120 mg) — Authority Required for bone metastases and hypercalcaemia of malignancy.
• Calcitonin — General Schedule.
• Calcium and vitamin D supplements — General Schedule.

Specialist referral in general practice

• Endocrinologist — all confirmed PHPT, normocalcaemic hyperparathyroidism, complex or PTH-independent hypercalcaemia, MEN syndromes.
• Endocrine surgeon — parathyroidectomy planning and surgery; outcomes are substantially better at high-volume centres.
• Renal physician — CKD-MBD (mineral and bone disorder), tertiary hyperparathyroidism, hypercalcaemia complicating acute kidney injury.
• Oncologist / palliative care — malignancy-related hypercalcaemia.
• Genetic counselling — MEN-1/2A, HPT-JT, FHH, and FIHP families.
• Endocrine Society of Australia (ESA) and ANZBMS provide professional guidelines and resources.
• Healthy Bones Australia — patient resources for osteoporosis management co-occurring with PHPT.

E. Special populations

Older adults. PHPT prevalence rises with age, particularly in postmenopausal women. Symptoms — fatigue, cognitive change, constipation — are easily attributed to ageing. Falls risk from neuromuscular involvement warrants attention alongside bone density assessment at cortical sites. Conservative management is more often preferred as surgical risk increases with comorbidity; cinacalcet and bone-protective therapy have a larger role in this group.

Pregnancy. PHPT in pregnancy carries risk of neonatal tetany and hypocalcaemia from rebound foetal parathyroid suppression. Surgical management in the second trimester is preferred when surgical criteria are met. Cinacalcet experience in pregnancy is limited; specialist obstetric and endocrine input is required. Coordination between endocrinology, endocrine surgery, and obstetrics is essential.

Paediatric and young adult patients. PHPT in patients under 40 warrants screening for genetic syndromes — MEN-1, MEN-2A, HPT-JT, and FIHP. Genetic counselling and family cascade screening should be arranged through an appropriate specialist service.

Chronic kidney disease. Secondary hyperparathyroidism (a physiological response to hypocalcaemia and hyperphosphataemia in CKD) may progress to autonomous tertiary hyperparathyroidism. Management is the domain of renal physicians — phosphate binders, active vitamin D analogues, calcimimetics, and selected parathyroidectomy under renal-specific criteria.

Lithium users. Lithium elevates the CaSR set-point, causing mild PTH-dependent hypercalcaemia in up to 10% of long-term users, and may unmask underlying PHPT. Where an alternative mood stabiliser is clinically appropriate, a trial of lithium cessation with psychiatric input clarifies the diagnosis.

Thiazide diuretic users. Thiazides raise serum calcium by increasing tubular reabsorption. Consider switching to an alternative antihypertensive if calcium is borderline elevated, then reassess after the diuretic has cleared.

When to escalate

Refer or escalate from general practice when:

• Hypercalcaemia confirmed on repeat testing — endocrinology review is appropriate for all confirmed PHPT.
• Corrected calcium above 3.0 mmol/L or symptomatic hypercalcaemia — emergency department or hospital admission.
• PTH suppressed with no clear explanation — oncology or haematology workup for malignancy.
• PHPT meeting any surgical criterion — endocrine surgical referral.
• Suspected genetic syndrome (MEN, HPT-JT, FHH, FIHP) — genetics referral and multidisciplinary input.
• PHPT with kidney stones — combined urology and endocrinology management.
• Elevated PTH with consistently normal calcium after adequate vitamin D repletion (normocalcaemic PHPT) — endocrinology.
• Tertiary hyperparathyroidism in CKD — renal physician.
• Parathyroid carcinoma suspected (severe hypercalcaemia, very high PTH, palpable neck mass) — urgent specialist referral.

What this article is and is not

This is general health information drawn from current Australian general practice guidelines — eTG complete, RACGP resources, NHMRC Nutrient Reference Values, ESA/ANZBMS position statements, and the Fourth International Workshop guidelines on primary hyperparathyroidism. It is not personal medical advice and does not create a doctor–patient relationship. Decisions about investigation and management, including whether to proceed to surgery, are made with your own GP and treating specialists.

For consumer-friendly information: HealthDirect, Healthy Bones Australia, Better Health Channel.

For urgent symptoms (severe confusion, vomiting, weakness): call 000 or attend your nearest emergency department.

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Sources cited

1. eTG complete — Hypercalcaemia and hyperparathyroidism
2. RACGP — Hypercalcaemia investigation in general practice
3. NHMRC — Nutrient Reference Values: Calcium and Vitamin D
4. Australian Medicines Handbook (AMH)
5. Endocrine Society of Australia / ANZBMS — Primary hyperparathyroidism
6. Bilezikian JP et al. — Fourth International Workshop on Asymptomatic Primary Hyperparathyroidism (JCEM 2014; updated 2022)
7. Walker MD, Silverberg SJ — Primary hyperparathyroidism (Nature Reviews Endocrinology 2018)
8. NICE NG132 — Primary hyperparathyroidism
9. PBS schedule
10. MBS Online
11. Healthy Bones Australia
12. HealthDirect — Calcium and your health