Possible mechanisms of hypercalcemia
Increased intake/absorption (intestinal)
Decreased loss (renal tubular reabsorption)
Increased bone resorption
Veterinary Literature
Midkiff et al:
- Retrospective of 20 cats with hypercalcemia (11.5-14.1 mg/dL)
- 14 cats had known dietary history: all on acidifying diets
- assays run: (not all tests run on all cats) total calcium, ionized calcium, PTH, PTHrP, calcitriol, 25, dihydroxycholecalciferol,
fractional excretion of calcium (spot checks only)
Therapy
Diet: 11/20, no response, except one concurrent treatment with steroids
Surgery: 2/20, transient (days) response, recurrence of hypercalcemia
Glucocorticoids: 6/20, 10-12.5 mg per cat per day 4/6 had complete response
2/6 had partial response (i.e. decrease in either total or ionized serum calcium but not both)
Prognosis
15/20 cats were alive 7 years past diagnosis
Savary KCM, et al
Retrospective of 71 cats with hypercalcemia and a clinical diagnosis
- Majority paraneoplastic or CRF
- 11/71: urolithiasis with no other diagnosis
o mean calcium 11.5 +/- 0.4 mg/dL
o significantly lower than paraneoplastic (mean 13.5+/- 2.5)
o of those with known dietary history, only ½ on acidifying diets
McClain HM et al:
- Retrospective of 5 cats who presented with lower urinary tract signs, CaOx urolithiasis
- On acidifying diets, switched to W/D, hypercalcemia resolved
- Due to decreased acid, or increased fiber with decreased intestinal absorption?
