| name | medication-induced-hypercalcemia-screener |
| description | Screen a hypercalcemic patient for medication- and supplement-induced causes — thiazides, lithium, vitamin D, vitamin A/retinoids, antiestrogens, theophylline, milk-alkali, SGLT2 inhibitors, immune checkpoint inhibitors, denosumab rebound, teriparatide/abaloparatide, foscarnet, ketogenic diet, aluminium. Trigger when a clinician asks "is this hypercalcemia drug-induced", "thiazide hypercalcemia", "lithium hypercalcemia", "denosumab rebound hypercalcemia", "vitamin D toxicity", "milk-alkali syndrome", "SGLT2 hypercalcemia", or any new hypercalcemia where medication review is needed. |
Medication-Induced Hypercalcemia — Screener
Run this skill on every new hypercalcemic patient before diagnosing PHPT or MAH. Drug- and supplement-induced hypercalcemia is reversible and easily missed.
STEP 1 — Take the medication & supplement history
Ask explicitly about:
- Prescription drugs — diuretics, mood stabilisers, oncology drugs, antivirals, osteoporosis injections
- OTC supplements — vitamin D, vitamin A, calcium, multivitamins, "bone health" preparations
- Antacids — calcium carbonate, milk-of-magnesia
- Recent injections — denosumab, teriparatide, abaloparatide, ICIs
- Recently stopped — denosumab discontinuation can cause rebound hypercalcemia
- Diet — ketogenic diet, large dairy intake, large vitamin D supplementation
STEP 2 — Match to the agent and act
Group A — Diuretics & mood stabilisers (PTH-dependent picture, mimics PHPT)
Thiazides
- Reduces renal Ca clearance. Typically only causes hypercalcemia in pre-existing PHPT or anephric patients.
- Action: stop the thiazide. Recheck Ca in 1–2 weeks. If still elevated → workup for PHPT.
Lithium
- 5% of users develop hypercalcemia. Shifts CaSR set-point upward + reduces renal Ca clearance.
- Action: stop or switch lithium if clinically possible (psychiatric collaboration). If lithium must continue and Ca is sustained high → consider PHPT workup; cinacalcet may be useful.
Group B — Vitamin / mineral excess
Vitamin D (D2, D3, 25(OH)D, calcitriol)
- Long half-life of cholecalciferol → hypercalcemia can persist weeks to months.
- Action: stop vitamin D. Hydration, calciuresis. Glucocorticoids + antiresorptive if severe. Restrict dietary calcium. Avoid sun.
Vitamin A / retinoids (cis-retinoic acid, ATRA) — >50,000 IU/day
- Mechanism: enhanced bone resorption.
- Action: stop, hydrate, antiresorptive if severe.
Milk-alkali syndrome — Ca carbonate ≥3 g/d + alkali (often modern OTC use)
- Triad: hypercalcemia + metabolic alkalosis + AKI / nephrocalcinosis.
- Action: stop calcium and antacid, rehydrate. Hemodialysis rarely.
Group C — Antiresorptive / anabolic bone agents
Denosumab — rebound hypercalcemia after discontinuation
- Most cases: children with bone tumours / fibrous dysplasia, occasionally adults with osteoporosis.
- Action: do not stop denosumab abruptly without bridging (bisphosphonate). If rebound has occurred → IV bisphosphonate, hydration.
Teriparatide [PTH(1-34)] / Abaloparatide [PTHrP analog]
- Transient hypercalcemia post-injection, resolves ~16 h.
- Action: confirm timing. If sustained → stop and reassess.
Group D — Oncology / antiviral / metabolic drugs
Antiestrogens (tamoxifen) — "tumour flare" hypercalcemia in breast cancer with bone mets
- Self-limiting; may need acute treatment (hydration, antiresorptive).
Theophylline / aminophylline
- Reversible on stopping; β-blockers can also help.
Foscarnet (antiviral, CMV)
- Rare; reversible on cessation.
Aluminum intoxication
- Setting: CKD on aluminium-containing phosphate binders, or contaminated dialysate / TPN.
- Action: stop aluminium source; chelate with desferrioxamine.
SGLT2 inhibitors
- Mechanism: osmotic diuresis + volume contraction, especially with co-existing risk factors (dehydration, thiazide, acidosis, undiagnosed PHPT).
- Action: hold drug, rehydrate, screen for PHPT.
Immune checkpoint inhibitors (ICIs)
- Mechanisms: ICI-induced hyperthyroidism / adrenal insufficiency / sarcoid-like granulomatosis / PTHrP / hyperprogression.
- Action: full workup including TSH, cortisol, PTHrP, imaging for new granulomas. Manage cause-specifically; glucocorticoids if granulomatous or adrenal.
Ketogenic diet (children with epilepsy)
- Mechanism: impaired osteoblast activity, reduced bone formation.
- Action: dietitian review; consider modifying ratio.
STEP 3 — Confirm reversibility
After stopping the suspected agent:
- Recheck corrected calcium at 1–2 weeks (longer for vitamin D — up to 8 weeks).
- If calcium normalises → diagnosis confirmed.
- If calcium remains elevated → return to the hypercalcemia-diagnostic-algorithm for PHPT, FHH, or MAH workup.
CLINICAL GUARDRAILS
- Drug-induced hypercalcemia can coexist with PHPT. Thiazide and lithium often unmask mild PHPT — recheck calcium after a 2–4 week washout before booking surgery.
- Vitamin D toxicity is long-lived. Cholecalciferol persists for weeks-to-months. Do not assume rapid resolution.
- Don't abruptly stop denosumab. Bridge with a bisphosphonate to prevent rebound resorption and hypercalcemia (especially in patients with high bone turnover).
- Lithium can't always be stopped. Coordinate with psychiatry; cinacalcet is an option in lithium-induced hypercalcemia who must continue lithium.
- OTC supplement load is often hidden. Ask about gummies, "bone-health" multivitamins, fish liver oil. Patients don't always volunteer these.
- ICIs cause endocrine mimics. A patient on pembrolizumab/nivolumab with hypercalcemia needs TSH, cortisol, ACTH, and chest imaging — not just a calcium recheck.
SOURCE
Bilezikian JP, Endotext. Approach to Hypercalcemia. NCBI Bookshelf NBK279129. Section: Medication-Induced Hypercalcemia (Thiazides, Lithium, Vitamin D, Vitamin A, Antiestrogens, Theophylline, Aluminum, Milk-Alkali, SGLT2i, ICIs, Denosumab, Teriparatide/Abaloparatide, Foscarnet, Ketogenic diet).
