Hypercalcemia in the cat: Not just idiopathic (Proceedings)

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?

Idiopathic hypercalcemic disorders in humans

Familial benign hypercalcemia

      Nonprogressive

      Hypocalciuric

      Normal PTH levels

      Normal D2 and D3 levels

      Don't respond to steroid therapy

Williams syndrome/Idiopathic infantile hypercalcemia

      Moderate to severe hypercalcemia

      Nephrocalcinosis with hypercaliuria

      Respond to steroid, calcitonin

      Decreased calcitonin levels, sometimes increases in calcitriol levels

      Can grow out of it

References

Midkiff AM, Chew DJ, Randolph JF, Center SA, DiBartola SP. Idiopathic hypercalcemia in cats. JVIM 2000 14:619-626.

Savary KCM, Price GS, Vaden SL. Hypercalcemia in cats: A retrospective study of 71 cats (1991-1997). JVIM 2000 14:184-189.

McClain HM, Barsanti JM, Bartges JW. Hypercalcemia and calcium oxaloate urolithiasis in cats: A report of 5 cases. JAAHA 1999 35:297-301.

Rodd C, Goodyer P. Hypercalcemia of the newborn: Etiology, evaluation, and management. Pediatr Nephrol 2000 14:354-355.

Shimizu H, Kodama S, Takeuchi A, Matui T. Idiopathic infantile hypercalcemia discovered in the newborn period. Acta Pediatrica Japonica 1994 36:720-723.

Alon U, Berkowitz D, Berant M. Idiopathic infantile hypercalcemia. Child Nephrol & Urol. 1992 12:47-50