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)
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