More to it than we thought… Approach to hypocalcemia!

Hypocalcemia: What is our approach??? If you’re anything like me, you’ve thought about this a lot less than hypercalcemia. We start the approach much like hypercalcemia: is this a PTH problem or is PTH an innocent bystander?

  1. Primary problem DUE TO LOW PTH
  • Destruction of the parathyroid glands most common
    • Surgery – may be transient, permanent, or even intermittent
    • Autoimmune (can be part of an inherited polyglandular autoimmune syndrome)
    • Uncommonly:
      • Radiation
      • Infiltrative (typical infiltrative diseases)
    • Congenital causes
  1. Not PTH’s Fault! – PTH levels variable
  • Vitamin D Deficiency
  • Advanced CKD
  • Extracellular deposition: (aka chelation): like hyperphosphatemia, osteoblastic mets, pancreatitis, and blood transfusions all chelate calcium
  • Sepsis/Critical Illness (80-90% incidence) – causes probably decreased secretion of PTH in critical illness. Lactate also chelates calcium! Check calciums frequently in critical illness – Remember this as this can contribute to hypotension in sepsis!
  • PTH resistance (pseudohypoparathyroidism)
  • Hypomagnesaemia – both decreases PTH secretion and increases PTH resistance
    • Happens more when Mg <0.8
    • Can’t correct the hypocalcemia until you correct the hypomagnesaemia!
  • DRUGS!!! Many drugs cause low calcium! While there are many, don’t forget about bisphosphonates and denosumab.
  1. Lastly, don’t forget about the fake-outs: LOW ALBUMIN
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