Renal & Urinary

Hypercalcemia: workup and treatment by severity

Clinical Overview and When to Suspect Hypercalcemia

— Mild: 10.5–11.9 mg/dL (often asymptomatic, outpatient workup)

— Moderate: 12.0–13.9 mg/dL (symptomatic, urgent management)

— Severe/hypercalcemic crisis: ≥14.0 mg/dL or symptomatic at any level → inpatient, IV therapy

— Outpatient (90%): Primary hyperparathyroidism — middle-aged women, incidental finding on routine chemistry panel

— Inpatient (65%): Malignancy (humoral hypercalcemia from PTHrP in squamous cell, renal, breast; osteolytic from myeloma, breast mets; 1,25-OH vit D from lymphoma)

— Together these account for >90% of cases

— Routine BMP showing elevated Ca on annual ambulatory visit

— Vague fatigue, constipation, polyuria, depression in older adult ("stones, bones, groans, psychiatric overtones, abdominal moans")

— Nephrolithiasis (especially recurrent calcium stones), osteoporosis, fragility fracture

— New AKI with shortened QT on ECG

— Confusion or lethargy in cancer patient — assume malignant hypercalcemia until proven otherwise

Definition: Serum calcium >10.5 mg/dL (corrected) or ionized Ca²⁺ >5.6 mg/dL

Correction formula: Corrected Ca = measured Ca + 0.8 × (4 − albumin). In critically ill or acid-base disturbance, order ionized calcium directly.

Epidemiology of etiology:

When to suspect:

Step 3 management: When you see Ca >10.5 on an asymptomatic outpatient panel, repeat the level with albumin before launching a workup — pseudohypercalcemia from dehydration or tourniquet stasis is common and avoids unnecessary endocrine referrals.

Board pearl: The two diagnoses to chase first are primary hyperparathyroidism (chronic, mild, outpatient) and malignancy (acute, severe, inpatient). The PTH level alone separates them in >95% of cases — order it on the first lab draw, not after a workup cascade.

Mortality risk: Severe hypercalcemia carries 30-day mortality up to 50% when from malignancy, largely reflecting underlying cancer burden rather than the calcium level itself.

Presentation Patterns and Key History

— Stones: Nephrolithiasis (calcium oxalate/phosphate), nephrocalcinosis, polyuria from nephrogenic DI

— Bones: Bone pain, osteitis fibrosa cystica (1° HPT), pathologic fracture (myeloma, mets), osteoporosis

— Groans: Abdominal pain, constipation, anorexia, nausea, peptic ulcer (gastrin↑), pancreatitis

— Thrones: Polyuria → dehydration → prerenal AKI (classic vicious cycle)

— Psychiatric overtones: Fatigue, depression, poor concentration, confusion, stupor, coma at Ca >14

— Chronic Ca of 12 in 1° HPT: often asymptomatic

— Acute Ca of 12 from PTHrP: confused, dehydrated, vomiting

— Duration: Years of mild elevation (HPT) vs. weeks (malignancy)

— Medications: Thiazides, lithium, vitamin D/A supplements, calcium carbonate (antacid abuse → milk-alkali), teriparatide

— Diet/supplements: OTC vitamin D megadoses, calcium chews for osteoporosis

— Cancer red flags: Weight loss, night sweats, smoking history, breast/prostate symptoms, lymphadenopathy

— Granulomatous clues: Cough, hilar adenopathy (sarcoid), TB exposure, fungal endemic area

— Family history: MEN1 (parathyroid + pituitary + pancreatic), MEN2A (parathyroid + medullary thyroid + pheo), FHH

The classic mnemonic — "Stones, Bones, Groans, Thrones, Psychiatric overtones":

Symptom severity correlates with rate of rise more than absolute level:

High-yield history questions:

Key distinction: Familial Hypocalciuric Hypercalcemia (FHH) vs. primary HPT — both have mildly elevated Ca and inappropriately normal/high PTH. FHH patients have a lifelong history of mild hypercalcemia, family members with the same finding, and 24-hr urine calcium <100 mg (or Ca/Cr clearance ratio <0.01). FHH needs no surgery — recognizing this prevents a futile parathyroidectomy.

Board pearl: A patient on a thiazide diuretic with new hypercalcemia → stop the thiazide and recheck Ca in 1–2 weeks. If still elevated, this often unmasks underlying 1° HPT. Thiazides alone rarely cause Ca >11.

Physical Exam Findings and Hemodynamic Assessment

— Hypercalcemia causes nephrogenic DI (calcium antagonizes ADH at collecting duct) → polyuria → volume depletion

— Dry mucous membranes, flat neck veins, orthostatic hypotension, tachycardia

— Decreased skin turgor, prolonged capillary refill

— This volume depletion worsens hypercalcemia by reducing renal Ca clearance — the cycle that justifies IV fluids as first-line therapy

— Mild: fatigue, weakness, hyporeflexia

— Moderate: confusion, lethargy, ataxia

— Severe (Ca >14): obtundation, stupor, coma

— Proximal muscle weakness (hard to rise from chair) classic for 1° HPT

— Bradycardia, hypertension (Ca potentiates vascular tone)

— Short QT interval, occasional AV block

— Digoxin toxicity potentiated — check level if patient on digoxin

— Band keratopathy (calcium deposits at corneal limbus) — chronic hypercalcemia

— Pruritus without rash — uremic-like, from Ca×PO₄ product

— Subcutaneous calcifications in chronic disease

— Brown tumors, "salt-and-pepper" skull (1° HPT — rare now)

— Lymphadenopathy (lymphoma → 1,25-vit D mediated)

— Breast exam, thyroid exam (parafollicular C cells)

— DRE in older men; skin survey for SCC

— Hepatosplenomegaly (myeloma, lymphoma)

Volume status — the most important exam finding:

Neurologic exam:

Cardiovascular:

Skin/extremities:

Cancer screening exam:

Step 3 management: Document orthostatic vitals at presentation — this drives your initial IV fluid rate. A patient with orthostasis and Ca 13 needs isotonic saline 200–300 mL/hr, not the cautious 75 mL/hr you'd use in CHF. Reassess volume q4–6h.

Board pearl: A confused elderly woman with constipation, weight loss, and Ca 13.5 has malignancy until proven otherwise. Don't anchor on dementia or depression — order PTH, PTHrP, and a CT chest/abdomen/pelvis early.

Diagnostic Workup — Initial Labs

— Repeat total calcium with albumin, or measure ionized Ca²⁺ directly

— Albumin correction: add 0.8 mg/dL per 1 g/dL albumin <4

— Elevated or inappropriately normal PTH (>20–25 pg/mL): PTH-dependent

— Primary hyperparathyroidism (>90%)

— Tertiary hyperparathyroidism (post-transplant, long-standing CKD)

— Familial hypocalciuric hypercalcemia (FHH)

— Lithium-induced

— Suppressed PTH (<20 pg/mL): PTH-independent → pursue malignancy, vitamin D, granulomatous, thyrotoxicosis

— PTHrP: Elevated in solid tumor humoral hypercalcemia (squamous lung, renal, breast, HPV-associated)

— 25-OH vitamin D: Elevated in vit D intoxication

— 1,25-(OH)₂ vitamin D (calcitriol): Elevated in granulomatous disease (sarcoid, TB, fungal) and lymphoma — extrarenal 1α-hydroxylase

— SPEP/UPEP, free light chains: Multiple myeloma

— TSH: Thyrotoxicosis causes mild hypercalcemia via bone resorption

— Phosphorus: Low in 1° HPT and PTHrP-mediated; high in vitamin D toxicity, milk-alkali

— BMP for Cr (AKI from volume depletion), bicarbonate (alkalosis in milk-alkali)

— 24-hr urine calcium: High in 1° HPT (>250 mg/d women, >300 men); low in FHH (<100 mg/d)

— Urine Ca/Cr clearance ratio: <0.01 = FHH; >0.02 = 1° HPT

— Short QT interval, occasionally Osborn waves, AV block at Ca >14

— Get one in any symptomatic patient or those on digoxin

Confirm hypercalcemia first:

The decisive first test — intact PTH:

Second-tier labs (order simultaneously to save time):

Renal and metabolic:

ECG:

CCS pearl: On the CCS case, the highest-yield single order set for new hypercalcemia is: CMP, ionized Ca, intact PTH, PTHrP, 25-OH and 1,25-OH vit D, TSH, SPEP, 24-hr urine Ca, ECG. Get these on arrival; the PTH result alone branches the entire algorithm.

Diagnostic Workup — Advanced and Confirmatory Studies

— Sestamibi parathyroid scan with SPECT/CT — preoperative localization of adenoma (~85% single adenoma, 15% 4-gland hyperplasia)

— Neck ultrasound — operator-dependent but radiation-free; often combined with sestamibi

— 4D-CT if both above non-diagnostic

— DEXA scan — assess cortical bone loss (distal radius most sensitive in HPT)

— Renal US — assess nephrolithiasis/nephrocalcinosis

— 24-hr urine Ca to exclude FHH before surgery — mandatory

— CT chest/abdomen/pelvis with contrast — solid tumors, lymphadenopathy

— Mammogram, colonoscopy if age-appropriate and not current

— PSA in older men

— Skeletal survey or PET/CT — myeloma lytic lesions, bone mets

— Peripheral smear + SPEP/UPEP/free light chains — myeloma

— ACE level, chest CT — sarcoidosis (low yield alone; CT is better)

— Bone marrow biopsy if myeloma suspected and SPEP positive

— Cortisol/ACTH — adrenal insufficiency rarely causes hypercalcemia

— CASR mutation if FHH suspected (low urine Ca, family history)

— MEN1, RET if multiple endocrine features or young patient

— Refer to genetics if positive — affects family screening

If PTH elevated → confirm primary hyperparathyroidism and localize:

If PTH suppressed → hunt for malignancy and granulomatous disease:

Genetic testing:

Key distinction: MEN1 vs MEN2A parathyroid disease — MEN1 nearly always 4-gland hyperplasia (subtotal parathyroidectomy with 3.5-gland removal or total with autotransplant); sporadic 1° HPT usually single adenoma (focused parathyroidectomy). Surgical approach differs — recognizing syndrome before OR matters.

Board pearl: A young patient (<40) with 1° HPT, multigland disease, or family history → screen for MEN1 (pituitary MRI, prolactin, IGF-1, gastrin, fasting glucose/insulin) before parathyroidectomy. Surgery without genetic context risks recurrence.

Step 3 management: Don't delay treatment of severe hypercalcemia waiting for advanced imaging. Treat the calcium first; image once stabilized.

Risk Stratification and Severity-Based Management Logic

— Mild (Ca 10.5–11.9, asymptomatic):

— Outpatient workup

— PO hydration (2–3 L/day water)

— Avoid thiazides, lithium, vitamin D/Ca supplements

— Mobilize patient (immobilization worsens it)

— Definitive treatment depends on etiology (e.g., parathyroidectomy for 1° HPT meeting criteria)

— Moderate (Ca 12.0–13.9, mildly symptomatic):

— Admit for IV fluids if symptomatic or AKI

— Outpatient feasible if truly asymptomatic and reliable follow-up

— IV normal saline 200–300 mL/hr titrated to UOP 100–150 mL/hr

— Consider calcitonin for rapid drop while bisphosphonate kicks in

— Severe (Ca ≥14 or any level with altered mental status, ECG changes, AKI):

— ICU or step-down admission

— Aggressive IV NS + calcitonin 4 IU/kg SC/IM q12h (acts in hours but tachyphylaxis at 48h)

— IV bisphosphonate (zoledronic acid 4 mg over 15 min, or pamidronate 60–90 mg over 2h) — onset 24–72h, duration 2–4 weeks

— Denosumab 60–120 mg SC if renal failure (CrCl <30) or bisphosphonate refractory

— Hemodialysis with low-Ca bath for Ca >18, renal failure, or CHF preventing fluids

— Age <50

— Serum Ca >1 mg/dL above ULN

— eGFR <60 or 24-hr urine Ca >400 mg

— Nephrolithiasis or nephrocalcinosis on imaging

— T-score ≤−2.5 or vertebral fracture

— Patient preference for cure

Triage by calcium level AND symptoms:

Indications for parathyroidectomy in asymptomatic 1° HPT (any one):

Step 3 management: Hypercalcemic crisis order set: IV NS 1 L bolus → 250–300 mL/hr; calcitonin 4 IU/kg SC q12h; zoledronic acid 4 mg IV; q4h ionized Ca, BMP, Mg, Phos; strict I/Os; foley if needed; ECG monitoring. Loop diuretics only AFTER euvolemia and only if volume overload threatens — they are no longer first-line.

Board pearl: Loop diuretics are NOT first-line. Old teaching of "saline + furosemide" caused harm by worsening volume depletion. Use furosemide only if you've fully volume-resuscitated and the patient is becoming overloaded (CHF, oliguric AKI).

Pharmacotherapy — First-Line Drug Regimen

— Restores volume, increases GFR, promotes calciuresis

— Rate: 200–300 mL/hr (1–2 L bolus first if severely depleted)

— Goal urine output: 100–150 mL/hr

— Lowers Ca by 1–3 mg/dL in 24–48h

— Caution in CHF, CKD, elderly — monitor lungs, JVP

— 4 IU/kg SC or IM q12h (can up-titrate to 8 IU/kg q6h)

— Onset 4–6 hours; lowers Ca 1–2 mg/dL

— Tachyphylaxis at 48–72h — useless beyond that

— Mechanism: inhibits osteoclasts, increases renal Ca excretion

— Use while waiting for bisphosphonate to kick in

— Zoledronic acid 4 mg IV over ≥15 min (preferred — more potent, single dose, lasts 4 weeks)

— Pamidronate 60–90 mg IV over 2–4 hours (alternative)

— Onset 24–72h; nadir at 4–7 days

— Renal dosing: Reduce zoledronic acid to 3 mg if CrCl 30–59; avoid if CrCl <30

— Adverse effects: Acute phase reaction (fever, myalgia in 30%), hypocalcemia (esp. if vit D deficient — replete first), osteonecrosis of jaw (rare with single doses), atypical femur fracture (chronic use)

— 60–120 mg SC (120 mg for malignancy)

— No renal dose adjustment — drug of choice if CrCl <30

— Onset 2–4 days; duration weeks–months

— Risk: severe rebound hypocalcemia — monitor Ca, Mg, vit D; replete before dosing

— More expensive; reserved for refractory cases

— Prednisone 20–60 mg PO daily or hydrocortisone 100 mg IV q8h

— Inhibits 1α-hydroxylase in granulomas; lymphoma cytolysis

— Onset 2–5 days

— Not effective for HPT or solid tumor PTHrP

— PO; activates CaSR on parathyroid → ↓PTH secretion

— Use in parathyroid carcinoma, severe 2°/3° HPT, or 1° HPT awaiting/declining surgery

IV isotonic saline — foundation of acute therapy:

Calcitonin (salmon) — rapid bridge:

IV bisphosphonates — definitive acute therapy:

Denosumab — for bisphosphonate failure or renal failure:

Glucocorticoids — granulomatous/lymphoma/vit D toxicity:

Cinacalcet (calcimimetic):

Board pearl: The trio for malignant hypercalcemia: saline + calcitonin + zoledronic acid. Saline starts immediately, calcitonin works in hours, zoledronate is the durable backbone. Denosumab if renal failure.

Procedures and Refractory Management

— Focused (minimally invasive) parathyroidectomy: Preoperative sestamibi/US localizes single adenoma; intraoperative PTH monitoring confirms cure (>50% drop at 10 min)

— Bilateral neck exploration: For 4-gland hyperplasia (MEN1, lithium-induced) — subtotal (3.5-gland) resection or total with forearm autotransplant

— Cure rate: >95% experienced surgeons

— Complications: Recurrent laryngeal nerve injury (1%), hypocalcemia ("hungry bone syndrome" — high turnover bone rapidly takes up Ca, PO₄, Mg postop)

— Check Ca, Mg, PO₄ at 6h and daily

— Treat hungry bone with oral calcium 1–3 g/day + calcitriol 0.25–0.5 mcg BID

— Watch for tetany, Chvostek/Trousseau, perioral numbness, prolonged QT

— Indications:

— Ca >18 mg/dL

— Severe symptoms (coma, arrhythmia) with renal failure

— CHF preventing aggressive fluids

— Failure of pharmacotherapy

— Lowers Ca by 3–6 mg/dL per session

— Continue medical therapy concurrently

— Cytoreductive chemotherapy, radiation, or surgery is the only durable fix

— Hypercalcemia of malignancy carries grim prognosis; hospice discussion appropriate when refractory

— Recheck adherence to NS, ensure calcitonin not >48h (tachyphylaxis)

— Add denosumab if zoledronate failed at 7 days

— Add glucocorticoids if granulomatous/lymphoma component

— Cinacalcet if parathyroid carcinoma

— Dialysis as bridge

Parathyroidectomy — definitive treatment for 1° HPT:

Postoperative monitoring:

Hemodialysis with low-calcium dialysate:

Treatment of underlying malignancy:

Refractory hypercalcemia algorithm:

CCS pearl: After parathyroidectomy, order Ca, Mg, Phos q6h x24h then daily, PTH on POD1, vitamin D, oral calcium carbonate 500 mg TID, calcitriol 0.25 mcg BID PRN. Discharge once Ca stable >8.0 off IV. Follow-up in clinic 1–2 weeks with repeat Ca and PTH.

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher baseline risk of confusion, falls, dehydration at lower Ca levels

— Polypharmacy: thiazides, vit D supplements, calcium carbonate (antacids, supplements) common contributors

— Slower IV fluid rates if CHF, diastolic dysfunction — 100–150 mL/hr with q4h reassessment of lungs/JVP

— Risk of digoxin toxicity ↑ with hypercalcemia — check level, hold digoxin if symptomatic

— Parathyroidectomy is safe and indicated even in 80s if symptomatic 1° HPT or meeting NIH criteria; age alone is not a contraindication

— Common: secondary HPT from phosphate retention, low calcitriol → can evolve to tertiary HPT (autonomous, hypercalcemic) post-transplant or after years

— Avoid zoledronic acid if CrCl <30; avoid pamidronate if CrCl <30

— Denosumab preferred for CKD hypercalcemia of malignancy — no renal dose adjustment

— Watch for severe rebound hypocalcemia with denosumab in CKD — replete vit D (calcitriol, not ergocalciferol) and Mg first

— Calcimimetics (cinacalcet, etelcalcetide) for 2°/3° HPT in dialysis patients

— Persistent hypercalcemia >12 months post-transplant

— Cinacalcet first-line; parathyroidectomy if refractory, severe bone disease, or graft dysfunction

— Less direct impact; check albumin (often low → use ionized Ca)

— Avoid acetaminophen-containing supplements if cirrhosis

— Bed-bound elderly or SCI patients develop hypercalcemia from unopposed bone resorption

— Treat with bisphosphonates and early mobilization — PT consult, weight-bearing as tolerated

Elderly considerations:

CKD (eGFR <60):

Tertiary HPT after kidney transplant:

Hepatic impairment:

Immobilized patients:

Step 3 management: Elderly nursing-home patient with new hypercalcemia + confusion → review med list FIRST (stop thiazide, vit D, Ca carbonate), check TSH, then PTH. Often reversible without admission. If Ca >12 or AKI, transfer to ED.

Board pearl: In CKD stage 4–5 with hypercalcemia, the diagnosis is rarely 1° HPT — think tertiary HPT, calcium-based phosphate binder excess, calcitriol overdose, or adynamic bone disease. PTH interpretation differs: in dialysis, target PTH is 2–9× ULN, not normal.

Special Populations — Pregnancy and Pediatrics

— 1° HPT in pregnancy is rare but high-risk: maternal preeclampsia, nephrolithiasis, hyperemesis; fetal IUGR, prematurity, neonatal hypocalcemic tetany (fetal parathyroids suppressed by maternal hypercalcemia)

— Diagnosis: Total Ca falls in pregnancy due to ↓albumin — use ionized Ca or albumin-corrected

— PTHrP normally elevated late pregnancy/lactation — interpret cautiously

— Treatment:

— Mild: hydration, monitor

— Severe or symptomatic: parathyroidectomy in 2nd trimester is preferred — safest window

— Avoid bisphosphonates (cross placenta, accumulate in fetal bone; pregnancy category D)

— Avoid denosumab in pregnancy

— Calcitonin is safe (does not cross placenta) — useful bridge

— Cinacalcet — limited data, avoid if possible

— Monitor for hypocalcemic tetany in first weeks (suppressed fetal PTH)

— May need calcium and calcitriol supplementation

— Williams syndrome: Idiopathic infantile hypercalcemia, elfin facies, supravalvular AS, intellectual disability

— Neonatal severe HPT (NSHPT): Homozygous CASR loss-of-function — life-threatening, requires urgent parathyroidectomy

— Heterozygous CASR mutation: FHH — benign, no treatment

— Vitamin D intoxication: OTC supplement errors in infants

— Subcutaneous fat necrosis of newborn — post-asphyxia, releases Ca from necrotic fat

— Jansen metaphyseal chondrodysplasia: Activating PTH1R mutation

— Malignancy (leukemia, rhabdomyosarcoma) — less common than adults

— Screen for MEN1/MEN2A — young age strongly suggests genetic syndrome

— Family history may be subtle (mom had "kidney stones")

Pregnancy:

Neonate of mother with hypercalcemia:

Pediatric hypercalcemia — distinct differential:

Adolescents with hypercalcemia:

Key distinction: FHH vs 1° HPT in pregnancy is critical — FHH needs no surgery and the neonate may also have FHH (benign). Don't operate on FHH; confirm with 24-hr urine Ca and family history.

Board pearl: A pregnant woman with Ca 12 and PTH 80 — get a 24-hr urine Ca (off thiazides). If urine Ca low, think FHH. If high, plan parathyroidectomy in 2nd trimester — safer than bisphosphonates and more durable than calcitonin.

Complications and Adverse Outcomes

— Acute kidney injury: Prerenal from volume depletion + nephrogenic DI; intrinsic from nephrocalcinosis

— Cardiac arrhythmia: Short QT, AV block, asystole at Ca >15; digoxin toxicity potentiated

— Coma: At Ca >14–15 with confusion progressing to obtundation

— Pancreatitis: Ca activates trypsinogen in pancreatic ducts

— Peptic ulcer disease: Hypercalcemia stimulates gastrin

— Death: From arrhythmia, aspiration, or underlying malignancy

— Nephrolithiasis (15–20% of 1° HPT) — calcium oxalate or phosphate

— Nephrocalcinosis → CKD progression

— Osteoporosis — cortical bone preferentially affected (distal radius DEXA most sensitive)

— Fragility fractures — wrist, vertebral, hip

— Cardiovascular: LVH, hypertension, vascular calcification

— Cognitive decline, depression — partially reversible with parathyroidectomy

— Peptic ulcer, pancreatitis — recurrent

— IV fluid overload — pulmonary edema in elderly/CHF

— Bisphosphonate:

— Acute phase reaction (fever, myalgia, fatigue 24–72h post-dose)

— Hypocalcemia (esp. vit D deficient — check 25-OH vit D and replete pre-treatment)

— Osteonecrosis of jaw (rare with single oncology doses; higher with chronic high-dose)

— Atypical femur fracture (chronic use >5y)

— Renal toxicity if infused too quickly

— Denosumab: Severe rebound hypocalcemia (esp. CKD), ONJ

— Calcitonin: Nausea, flushing, hypersensitivity, tachyphylaxis

— Glucocorticoids: Hyperglycemia, immunosuppression, mood

— Hungry bone syndrome: Severe hypocalcemia + hypophosphatemia + hypomagnesemia in first days–weeks; requires aggressive Ca + calcitriol

— Recurrent laryngeal nerve injury, neck hematoma, persistent/recurrent HPT

Acute (severe hypercalcemia):

Chronic (untreated mild–moderate hypercalcemia, esp. 1° HPT):

Treatment-related complications:

Post-parathyroidectomy:

Board pearl: Before giving IV zoledronate, check 25-OH vitamin D. If <20 ng/mL, replete first or risk severe symptomatic hypocalcemia. In urgent cases, give bisphosphonate but co-administer oral calcium + calcitriol.

Step 3 management: Discharge counseling should include signs of hypocalcemia (perioral numbness, cramps, Chvostek) post-bisphosphonate or post-parathyroidectomy, with clear return precautions.

When to Escalate Care — ICU, Consult, and Inpatient Triage

— Calcium ≥14 mg/dL regardless of symptoms

— Altered mental status, obtundation, coma

— ECG changes: short QT with arrhythmia, AV block, ventricular ectopy

— Hemodynamic instability

— Severe AKI with anuria → needs urgent dialysis

— Pulmonary edema preventing aggressive IV fluids → needs dialysis

— Pancreatitis with hemodynamic compromise

— Calcium 12–14 with symptoms

— Symptomatic AKI

— Inability to tolerate PO (vomiting)

— Unreliable outpatient follow-up

— New malignancy workup needed

— Asymptomatic Ca 10.5–11.9

— Mild symptoms with Ca <12 and normal renal function

— Reliable patient, ability to maintain PO hydration

— Follow-up within 1–2 weeks confirmed

— Endocrinology: All confirmed 1° HPT, MEN syndromes, refractory cases, FHH workup

— Endocrine surgery: For parathyroidectomy planning

— Nephrology: Dialysis indication, CKD with hypercalcemia, refractory AKI

— Oncology: Malignancy-associated hypercalcemia, especially newly diagnosed

— Hematology: Suspected myeloma (SPEP/UPEP positive, lytic lesions)

— Palliative care: Recurrent malignant hypercalcemia signals poor prognosis — early integration

— Ca >18 mg/dL

— Severe symptoms + renal failure

— CHF/anuria preventing IV fluids

— Refractory to all medical therapy at 48h

ICU/step-down admission criteria:

General medicine admission:

Outpatient management acceptable:

Consultations to consider:

Indications for hemodialysis:

CCS pearl: On CCS, for a patient with Ca 16, AMS, and Cr 3.5: transfer to ICU, call nephrology for emergent HD, start IV NS 200 mL/hr (cautiously), calcitonin 4 IU/kg SC q12h, denosumab 120 mg SC (not zoledronate — renal failure), continuous telemetry, q4h ionized Ca. Don't wait 24h on bisphosphonates that won't work.

Board pearl: Hypercalcemia of malignancy >14 without prior chemotherapy plan signals goals of care discussion. Median survival post-episode is 30–60 days untreated cancer. Step 3 stems often probe whether you'll initiate palliative care alongside calcium-lowering therapy — the answer is yes.

Key Differentials — PTH-Dependent Causes

— Single adenoma (80–85%), 4-gland hyperplasia (10–15%), parathyroid carcinoma (<1%)

— Middle-aged women predominate; often incidental on routine labs

— Labs: ↑Ca, ↑/inappropriately normal PTH, ↓PO₄, ↑urine Ca, ↑Cl/PO₄ ratio (>33 classic)

— Imaging: sestamibi + neck US; DEXA (distal radius); renal US for stones

— Treatment: parathyroidectomy if criteria met; observation otherwise

— Autonomous PTH secretion after long-standing secondary HPT (CKD, prolonged vit D deficiency)

— Classic setting: post-renal transplant patient with persistent hypercalcemia

— Treatment: cinacalcet; subtotal parathyroidectomy if refractory

— Autosomal dominant CASR loss-of-function — set point for Ca shifted upward

— Lifelong mild hypercalcemia, family members affected

— Urine Ca <100 mg/24h or Ca/Cr clearance ratio <0.01 (vs 1° HPT >0.02)

— No treatment, no surgery — failure to recognize leads to unnecessary parathyroidectomy with no cure

— Genetic counseling for family

— Lithium shifts CaSR set point → mild ↑Ca, ↑PTH, ↓urine Ca (mimics FHH)

— Develops months–years into therapy

— Management: continue lithium if psychiatrically stable, monitor; switch if severe

— Parathyroidectomy if Ca persistently elevated and lithium cannot be stopped — usually 4-gland hyperplasia

— MEN1: Parathyroid (>90%) + pituitary + pancreatic NETs (gastrinoma, insulinoma); MEN1 gene

— MEN2A: Medullary thyroid + pheochromocytoma + parathyroid (20%); RET gene

— Screen young (<40) HPT patients

Primary hyperparathyroidism (>85% of outpatient hypercalcemia):

Tertiary hyperparathyroidism:

Familial hypocalciuric hypercalcemia (FHH):

Lithium-induced hypercalcemia:

MEN syndromes:

Key distinction: FHH vs 1° HPT — both have ↑Ca, ↑/normal PTH. The differentiator is 24-hr urine Ca: low in FHH, high-normal/high in HPT. Always check before scheduling surgery.

Board pearl: A patient on lithium for 5 years with new Ca 11.2 and PTH 75 — this is lithium-mediated, not coincidental 1° HPT in 90% of cases. Try lithium discontinuation/switch before surgical referral.

Key Differentials — PTH-Independent Causes

— Humoral hypercalcemia of malignancy (PTHrP):

— Squamous cell (lung, head/neck, esophagus, cervix), renal cell, breast, ovarian, HTLV-1 lymphoma

— Mimics PTH biochemistry: ↑Ca, ↓PO₄, ↑urine Ca, but PTH suppressed, PTHrP elevated

— Osteolytic metastases:

— Breast cancer, multiple myeloma, lung

— Direct bone resorption by tumor cells via RANKL

— SPEP/UPEP if myeloma suspected

— 1,25-(OH)₂ vit D-mediated (tumor):

— Hodgkin and non-Hodgkin lymphoma — ectopic 1α-hydroxylase

— Elevated calcitriol; treat with glucocorticoids + tumor therapy

— Ectopic PTH secretion: extremely rare (some ovarian, lung tumors)

— Sarcoidosis, tuberculosis, histoplasmosis, coccidioidomycosis, berylliosis, GPA

— Macrophages in granulomas express 1α-hydroxylase

— Treatment: glucocorticoids; treat underlying disease; sun/vit D avoidance

— OTC megadose supplements, prescription calcitriol overdose

— ↑25-OH vit D (>150 ng/mL) and/or ↑1,25-OH vit D

— Treatment: stop supplement, hydration, glucocorticoids if severe

— Megadose supplements, isotretinoin

— Stimulates osteoclasts → hypercalcemia + headaches, alopecia, hepatotoxicity

— Mild hypercalcemia from accelerated bone turnover

— Check TSH; treat hyperthyroidism

— Excess Ca carbonate (antacids, supplements >3 g/day Ca) + absorbable alkali

— Triad: hypercalcemia + metabolic alkalosis + AKI

— Treatment: stop calcium, IV fluids

— Especially in young (Paget) or paraplegic patients

— High bone turnover unopposed

— Treatment: mobilization + bisphosphonate

Malignancy (most common cause of inpatient hypercalcemia):

Granulomatous diseases (1,25-vit D mediated):

Vitamin D intoxication:

Vitamin A intoxication:

Thyrotoxicosis:

Milk-alkali syndrome:

Immobilization:

Adrenal insufficiency, pheochromocytoma, VIPoma — uncommon

Board pearl: Mnemonic for PTH-independent hypercalcemia: "CHIMPANZEES" — Calcium supplementation/milk-alkali, Hyperparathyroidism (1° secondary), Iatrogenic/Immobilization, Multiple myeloma, Paget/Parenteral nutrition, Addison/Acromegaly, Neoplasm, Zollinger-Ellison (MEN1), Excess vit D, Excess vit A, Sarcoidosis.

Secondary Prevention, Discharge Medications, and Long-Term Plan

— If parathyroidectomy: Curative; follow Ca + PTH at 6 months then annually

— Calcium supplement 1000–1200 mg/day + vit D 800–2000 IU/day post-op (lifelong if needed for bone)

— DEXA at 1 year, then q2y; bone density typically improves

— Stop calcium/vit D supplements pre-op; resume post if hungry bone

— If observation (asymptomatic, not meeting criteria):

— Annual serum Ca, Cr, eGFR

— DEXA every 1–2 years (lumbar, hip, distal radius)

— Vitamin D repletion to 25-OH vit D >30 ng/mL (cautiously — paradoxically helps)

— Adequate calcium intake 1000–1200 mg/day (restriction worsens HPT)

— Hydration; avoid thiazides, lithium

— Annual renal US or non-contrast CT if stones suspected

— Refer for surgery if criteria develop

— Definitive treatment is cancer therapy

— Recurrent episodes: scheduled zoledronate q4 weeks or denosumab q4 weeks SC

— Hospice/palliative care integration — median survival <60 days untreated

— Avoid thiazides, vit D supplements, calcium-containing antacids

— Maintain low-vitamin D diet, sun avoidance

— Glucocorticoids for active disease

— Hydroxychloroquine, methotrexate as steroid-sparing in sarcoidosis

— STOP: thiazides (switch to loop or other antihypertensive), lithium (if feasible), vitamin D megadoses, calcium carbonate antacids, calcium supplements >1200 mg/day

— CONTINUE/ADD: modest vit D if deficient, mobilization, hydration counseling

— No treatment; genetic counseling, family screening

— Avoid unnecessary workup/surgery

— Wear medical alert if severe

Primary hyperparathyroidism — long-term:

Malignancy-associated hypercalcemia:

Granulomatous disease:

Medication reconciliation at discharge:

FHH:

Step 3 management: Discharge plan for new 1° HPT not meeting surgery criteria: Ca + Cr q6 months, DEXA in 1 year, 24-hr urine Ca, renal US, calcium/vit D dietary counseling (don't restrict), avoid thiazide, endocrinology follow-up in 3 months.

Board pearl: Vitamin D deficiency is common in 1° HPT and worsens secondary HPT-like physiology. Replete 25-OH vit D to 30+ ng/mL slowly even in mild hypercalcemia — paradoxically, Ca often does not rise further and PTH falls.

Follow-Up, Monitoring, and Counseling

— Day 3–7 post-discharge: BMP for Ca, Cr, electrolytes

— 2 weeks: clinic visit, full workup review, ensure outpatient labs sent (PTH, PTHrP, vit D, SPEP if indicated)

— 4 weeks: repeat Ca; bisphosphonate effect peaks then wanes

— Schedule next zoledronate dose at 4 weeks if malignancy

— POD #1: Ca, PTH (should drop >50% intraoperatively)

— Week 1: clinic visit, wound check, Ca

— 6 months: Ca, PTH, vit D, DEXA baseline

— Annually thereafter: Ca, PTH (rule out persistent/recurrent disease)

— Serum Ca + Cr + eGFR annually

— DEXA every 1–2 years — lumbar, hip, distal radius (cortical bone)

— 24-hr urine Ca every 1–2 years

— Renal imaging (US or non-contrast CT) every 1–2 years

— Refer for surgery if: Ca rises >1 mg/dL above ULN, eGFR falls below 60, new stone, T-score worsens to ≤−2.5, age <50

— Hydration: 2–3 L/day, especially during illness/diarrhea

— Calcium intake: Don't over-restrict; aim 1000–1200 mg/day from diet

— Medications to avoid: thiazides, lithium, vit D megadoses, excess calcium carbonate

— Activity: weight-bearing exercise for bone health

— Symptoms to report: confusion, severe constipation, polyuria, flank pain (stone), perioral numbness (hypocalcemia post-op)

— Smoking/alcohol cessation for bone health

— Bisphosphonate (alendronate, risedronate) if T-score ≤−2.5 and not having surgery

— Denosumab alternative

— Adequate vit D and calcium

Acute hospitalization follow-up:

Post-parathyroidectomy follow-up:

Asymptomatic 1° HPT (observation) monitoring:

Counseling points:

Bone health (if osteoporosis present):

Step 3 management: Provide written discharge instructions listing: medications stopped, follow-up dates, target labs, hydration goal, symptoms to return for, contact number. Transitions of care failures (no labs at 1 week, missed endo appt) cause readmission — a tested Step 3 systems issue.

Board pearl: Recurrent hypercalcemia after parathyroidectomy in <6 months suggests incomplete resection or multigland disease (MEN1); re-image with sestamibi + 4D-CT and consider MEN1 gene testing. After 6 months, consider recurrence of disease.

Ethical, Legal, and Patient Safety Considerations

— Recurrent hypercalcemia of malignancy carries median survival of weeks to months — it is a terminal event marker

— Step 3 expects you to initiate goals of care discussions when treating second/third episodes

— Document advance directive, code status, hospice eligibility

— Avoid futile escalation (e.g., dialysis in actively dying patient unless aligned with patient wishes)

— Discuss: cure rate >95%, RLN injury (1%), neck hematoma, persistent HPT (5%), permanent hypocalcemia (<1%), conversion to bilateral exploration if intraop PTH inadequate

— Special concern: patient with cognitive impairment — ensure surrogate decision-maker involvement; document capacity assessment

— Pregnant patient: discuss timing (2nd trimester), fetal risk of surgery vs. untreated maternal/fetal risk

— Most common error: failure to recheck Ca within 1–2 weeks post-discharge → readmission with rebound or persistent hypercalcemia

— Medication reconciliation MUST include stopping thiazide, lithium, vit D supplements

— Communicate discharge plan directly to PCP — fax/portal/phone — within 24h

— Pending labs (PTHrP, SPEP) at discharge need ownership: who reviews? Schedule follow-up before result returns

— Pediatric hypercalcemia from vitamin D OTC overdose may trigger child welfare evaluation if pattern suggests neglect or Munchausen by proxy

— Document carefully; involve social work for repeated cases

— Inadvertent thiazide continuation or missed FHH diagnosis leading to unnecessary surgery requires honest disclosure to patient per AMA ethics — Step 3 ethics stems test the duty to disclose

— Apologize, explain, document; root-cause analysis

— Sarcoidosis disproportionately affects Black patients — consider it earlier in differential

— Access to parathyroidectomy varies; refer to high-volume centers for best outcomes

— Hypercalcemia in dying patient: focus on symptom relief (sedation for confusion, antiemetics, mouth care for dehydration) — calcium-lowering therapy may not align with comfort-only goals; discuss with family

Goals of care in malignant hypercalcemia:

Informed consent for parathyroidectomy:

Patient safety — transitions of care:

Mandatory reporting and screening:

Disclosure of medical errors:

Health equity:

End-of-life considerations:

Board pearl: When a patient on hospice presents with hypercalcemia and confusion, the default is NOT to admit and treat — confirm goals of care first. Treating reversible delirium that distresses the family may be appropriate; admitting for dialysis usually is not.

Step 3 management: Document capacity assessment in confused hypercalcemic patients before obtaining consent for invasive procedures. Confusion from hypercalcemia is reversible — once Ca corrected, reassess capacity and re-consent.

High-Yield Associations and Rapid-Fire Clinical Facts

— IV saline: hours

— Calcitonin: 4–6 hours (tachyphylaxis at 48h)

— Zoledronate: 24–72 hours, peaks 4–7 days, lasts 2–4 weeks

— Denosumab: 2–4 days, lasts weeks

— Glucocorticoids: 2–5 days (granuloma/lymphoma only)

— Dialysis: hours

— Age <50

— Ca >1 above ULN

— eGFR <60 OR urine Ca >400/d

— T-score ≤−2.5 OR vertebral fracture

— Nephrolithiasis/nephrocalcinosis

— Outpatient hypercalcemia: 1° HPT

— Inpatient hypercalcemia: malignancy

— Hypercalcemia with high PTH: 1° HPT

— Hypercalcemia with low PTH: malignancy

Primary HPT triad: ↑Ca, ↑PTH, ↓PO₄

PTHrP triad: ↑Ca, ↓PTH, ↓PO₄, malignancy history

Vit D toxicity triad: ↑Ca, ↓PTH, ↑PO₄, ↑25-OH vit D

Milk-alkali triad: ↑Ca + metabolic alkalosis + AKI

FHH: ↑Ca, normal/↑PTH, ↓urine Ca (<100 mg/24h)

Sarcoid/lymphoma: ↑Ca, ↓PTH, ↑1,25-OH vit D

Mnemonic for symptoms: "Stones, bones, groans, thrones, psychiatric overtones"

Mnemonic for causes: CHIMPANZEES (Calcium intake, Hyperparathyroidism, Iatrogenic/Immobilization, Multiple myeloma, Paget/Parenteral nutrition, Addison/Acromegaly, Neoplasm, Zollinger-Ellison/MEN, Excess vit D, Excess vit A, Sarcoidosis)

ECG: Short QT, occasionally J wave, AV block, ventricular ectopy at Ca >14

Digoxin toxicity potentiated by hypercalcemia

Calcium-creatinine clearance ratio: <0.01 = FHH; >0.02 = 1° HPT

Albumin correction: Add 0.8 mg/dL per 1 g/dL albumin <4. In acidosis or critical illness, measure ionized

Treatment onset times:

NIH criteria for parathyroidectomy in asymptomatic 1° HPT (any one):

MEN1: Parathyroid + Pituitary + Pancreas (3 P's)

MEN2A: Medullary thyroid + Pheo + Parathyroid

Most common cause of:

Drugs causing hypercalcemia: thiazides, lithium, vit D, vit A, calcium carbonate, teriparatide, theophylline (rare), tamoxifen (transient flare)

Bisphosphonate ADRs: acute phase reaction, hypocalcemia, ONJ, atypical femur fracture, renal toxicity

Board pearl: A calcium-to-phosphorus ratio >3 with hypercalcemia is highly suggestive of 1° HPT or PTHrP (both phosphaturic). When PO₄ is normal/high, think vit D, milk-alkali, immobilization.

Board Question Stem Patterns

"55F routine physical, Ca 11.2, repeat 11.4, asymptomatic. PTH 88." → 1° HPT. Next: 24-hr urine Ca (rule out FHH), DEXA, renal US. Surgery if criteria met.

"63M lung cancer (squamous), confused, Ca 14.5, Cr 2.0, PTH suppressed, PTHrP elevated." → Humoral hypercalcemia of malignancy. Treatment: IV NS + calcitonin + zoledronate (if Cr improves) or denosumab. Discuss goals of care.

"42F Black woman with dyspnea, cough, bilateral hilar adenopathy, Ca 11.8, PTH low, 1,25-OH vit D elevated." → Sarcoidosis. Treatment: prednisone, sun/vit D avoidance.

"28M Ca 10.9 (chronic since teens), PTH 65, urine Ca 65 mg/24h. Father had 'asymptomatic high calcium'." → FHH. Do not operate. Genetic counseling.

"50F bipolar on lithium 8 years, Ca 11.1, PTH 70." → Lithium-induced. Trial discontinuation/switch first.

"65F osteoporosis taking 6 g Ca carbonate/day, Ca 13, HCO₃ 32, Cr 2.5, PTH suppressed." → Milk-alkali syndrome. Stop calcium, IV fluids.

"68M lethargic, Ca 16, Cr 3.5, ECG short QT, anuric." → ICU + hemodialysis, not just zoledronate.

"POD #1 after parathyroidectomy, Ca 7.2, tingling lips, Chvostek positive." → Hungry bone syndrome. IV calcium gluconate, then oral Ca + calcitriol.

"60F on HCTZ 5 years, Ca 11.0. Stop HCTZ, recheck in 2 weeks." → If still elevated, workup for 1° HPT.

"25M Ca 11.5, PTH 90, gastrinoma, prolactinoma." → MEN1. Genetic testing, screen family, parathyroidectomy is subtotal/total (4-gland hyperplasia).

"30F 18 weeks pregnant, Ca 12, symptomatic, PTH 100." → Parathyroidectomy in 2nd trimester. Avoid bisphosphonates.

Stem 1 — Asymptomatic incidental:

Stem 2 — Malignancy with severe hypercalcemia:

Stem 3 — Granulomatous disease:

Stem 4 — FHH masquerade:

Stem 5 — Lithium-induced:

Stem 6 — Milk-alkali:

Stem 7 — Hypercalcemic crisis:

Stem 8 — Post-parathyroidectomy:

Stem 9 — Thiazide unmasking:

Stem 10 — MEN1:

Stem 11 — Pregnancy:

Step 3 management: When the stem mentions recent IV bisphosphonate + new perioral numbness, the answer is hypocalcemia from undiagnosed vit D deficiency — check 25-OH vit D, treat with IV calcium gluconate and calcitriol.

Board pearl: When asked "next best step" in newly discovered hypercalcemia, the answer is almost always measure intact PTH (if not already done) — it branches every downstream decision.

One-Line Recap

Hypercalcemia workup hinges on the PTH level — elevated/inappropriately normal PTH points to primary hyperparathyroidism (after excluding FHH and lithium), suppressed PTH points to malignancy, vitamin D-mediated, or granulomatous disease, and severity-based treatment escalates from oral hydration in mild outpatient disease, to IV saline + calcitonin + IV bisphosphonate (or denosumab if renal failure) in moderate-to-severe disease, to hemodialysis in life-threatening crisis.

— Confirm with ionized or albumin-corrected Ca → measure intact PTH first → PTH-dependent (1° HPT, FHH, lithium, MEN) vs PTH-independent (malignancy, vit D, granuloma, milk-alkali) → confirm with PTHrP, 25-OH and 1,25-OH vit D, SPEP, 24-hr urine Ca, CT imaging as branched

— Mild (10.5–11.9): outpatient, hydration, stop offenders, treat cause

— Moderate (12–13.9): IV NS, calcitonin, bisphosphonate

— Severe (≥14 or symptomatic): ICU, aggressive saline, calcitonin + zoledronate/denosumab, dialysis if refractory

— 1° HPT meeting criteria: parathyroidectomy (cure rate >95%)

— Malignancy: treat the cancer; recurrent episodes signal poor prognosis and goals-of-care discussion

— Granulomatous/lymphoma: glucocorticoids

— FHH: no treatment, genetic counseling

Diagnostic algorithm:

Severity-based treatment:

Definitive treatments:

Step 3 management: Always reconcile medications (stop thiazide, lithium, vit D, Ca carbonate), confirm vitamin D status before bisphosphonate, ensure follow-up Ca check within 1–2 weeks of discharge, and integrate palliative care early in recurrent malignant hypercalcemia.

Board pearl: The single most common test that distinguishes the two highest-yield diagnoses (1° HPT vs malignancy) is the PTH level, and the single most common pitfall is operating on a patient with FHH — always check 24-hr urine calcium before parathyroidectomy.