Thread by @AaronGoodman33

Hypercalcemia: A Tweetorial for Internist

Calcium regulated to levels between 9-10.5 mg/dL

↑PTH = ↑calcium
↑Calcitonin = ↓calcium

PTH produced by the chief cells in parathyroid glands
Calcitonin produced by the parafollicular cells in thyroid

PTH = ⬆️Ca ⬇️Phos

↑renal reabsorption Ca in distal tubule
↑urinary Phos excretion
↑release Ca from bones
Binds osteoblasts ↑ RANKL -> activates osteoclasts

↑25-OH D3 1-α hydroxylase -> vit D to active form (1,25-dihydroxy)
Active vit D ↑absorption of intestinal Ca

Causes of Hypercalcemia

Primary hyperparathyroidism

Malignancy (3 mechanisms):
Osteolytic mets
PTHrP (squamous cell lung cancer)
↑production of active vitamin D (NHL)

Meds:
Lithium
Thiazides diuretics

Thyrotoxicosis
Milk alkali syndrome
Familial hypocalciuric hypercalcemia

Clinical Manifestations

"stones, bones, abdominal groans, thrones and psychiatric overtones"

Renal:
Polyuria
Polydipsia

GI:
Anorexia
N/V
Pancreatitis

MSK:
Weakness
Bone pain

Neurologic:
Confusion
Stupor/coma

Cardiovascular:
Shortened QT
Bradycardia
Hypertension

Check ionized Calcium to make sure calcium is truly elevated!

Changes in albumin will affect total serum calcium without changing the level of free calcium. (decreased albumin --> decreased total Ca--> constant free Ca)

Corrected Ca = [Measured Ca] + 0.8 x [4.0-Albumin]

Diagnostic workup

First check PTH

If ⬆️ PTH
Measure urine 24 hour calcium

If ⬇️24 hr urine Ca->Familial hypocalciuric hypercalcemia
If ⬆️ 24 hr urine Ca
perform parathyroid scan (Sestamibi)
Likely primary hyperparathyroidism

If ⬇️PTH
Check meds
Start worrying about cancer!

Treatment of Hypercalcemic crisis

Replace IV fluids first!
At least 20-30 ml/kg (2L) IV NS
Avoid lasix unless volume overload!

Bisphosphonate
Zoledronic acid 4 mg IV over 15 minutes
Caution with kidney failure

Calcitonin SC
Tachyphylaxis occurs (stops working after few doses)